



Network Working Group                                  J. Preuß Mattsson
Internet-Draft                                               G. Selander
Updates: 6698 (if approved)                                  Ericsson AB
Intended status: Standards Track                                 S. Raza
Expires: 25 December 2025                                     J. Höglund
                                                                 RISE AB
                                                              M. Furuhed
                                                             Nexus Group
                                                            23 June 2025


          CBOR Encoded X.509 Certificates (C509 Certificates)
                  draft-ietf-cose-cbor-encoded-cert-14

Abstract

   This document specifies a CBOR encoding of X.509 certificates.  The
   resulting certificates are called C509 Certificates.  The CBOR
   encoding supports a large subset of RFC 5280 and all certificates
   compatible with the RFC 7925, IEEE 802.1AR (DevID), CNSA 1.0, RPKI,
   GSMA eUICC, and CA/Browser Forum Baseline Requirements profiles.
   When used to re-encode DER encoded X.509 certificates, the CBOR
   encoding can in many cases reduce the size of RFC 7925 profiled
   certificates with over 50% while also significantly reducing memory
   and code size compared to ASN.1.  The CBOR encoded structure can
   alternatively be signed directly ("natively signed"), which does not
   require re-encoding for the signature to be verified.  The TLSA
   selectors registry defined in RFC 6698 is extended to include C509
   certificates.  The document also specifies C509 Certificate Requests,
   C509 COSE headers, a C509 TLS certificate type, and a C509 file
   format.

About This Document

   This note is to be removed before publishing as an RFC.

   Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-ietf-cose-cbor-encoded-cert/.

   Discussion of this document takes place on the CBOR Object Signing
   and Encryption Working Group mailing list (mailto:cose@ietf.org),
   which is archived at https://mailarchive.ietf.org/arch/browse/cose/.
   Subscribe at https://www.ietf.org/mailman/listinfo/cose/.

   Source for this draft and an issue tracker can be found at
   https://github.com/cose-wg/CBOR-certificates.





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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 25 December 2025.

Copyright Notice

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   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   5
   3.  C509 Certificate  . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Message Fields  . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Encoding of subjectPublicKey and issuerSignatureValue . .  11
     3.3.  Encoding of Extensions  . . . . . . . . . . . . . . . . .  12
     3.4.  COSE Header Parameters  . . . . . . . . . . . . . . . . .  17
     3.5.  Private Key Structures  . . . . . . . . . . . . . . . . .  19
     3.6.  Deterministic Encoding  . . . . . . . . . . . . . . . . .  19
   4.  C509 Certificate (Signing) Request  . . . . . . . . . . . . .  20
     4.1.  Certificate Request Types . . . . . . . . . . . . . . . .  21
     4.2.  Subject Signature Algorithm . . . . . . . . . . . . . . .  22
     4.3.  Certificate Request Attributes  . . . . . . . . . . . . .  22
     4.4.  Certificate Request Template  . . . . . . . . . . . . . .  23
   5.  C509 Processing and Certificate Issuance  . . . . . . . . . .  24



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   6.  Legacy Considerations . . . . . . . . . . . . . . . . . . . .  25
   7.  Expected Certificate Sizes  . . . . . . . . . . . . . . . . .  26
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  27
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  27
     9.1.  C509 Certificate Types Registry . . . . . . . . . . . . .  28
     9.2.  C509 Certificate Request Types Registry . . . . . . . . .  28
     9.3.  C509 Private Key Types  . . . . . . . . . . . . . . . . .  29
     9.4.  C509 Attributes Registry  . . . . . . . . . . . . . . . .  30
     9.5.  C509 Extensions Registry  . . . . . . . . . . . . . . . .  34
     9.6.  C509 Certificate Policies Registry  . . . . . . . . . . .  38
     9.7.  C509 Policies Qualifiers Registry . . . . . . . . . . . .  41
     9.8.  C509 Information Access Registry  . . . . . . . . . . . .  41
     9.9.  C509 Extended Key Usages Registry . . . . . . . . . . . .  43
     9.10. C509 General Names Registry . . . . . . . . . . . . . . .  45
     9.11. C509 Signature Algorithms Registry  . . . . . . . . . . .  47
     9.12. C509 Public Key Algorithms Registry . . . . . . . . . . .  51
     9.13. COSE Header Parameters Registry . . . . . . . . . . . . .  54
     9.14. Media Type application/cose-c509-cert . . . . . . . . . .  54
     9.15. Media Type application/cose-c509-pkcs10 . . . . . . . . .  55
     9.16. Media Type application/cose-c509-privkey  . . . . . . . .  56
     9.17. Media Type application/cose-c509-pem  . . . . . . . . . .  57
     9.18. Media Type application/cose-certhash  . . . . . . . . . .  58
     9.19. CoAP Content-Formats Registry . . . . . . . . . . . . . .  60
     9.20. TLS Certificate Types Registry  . . . . . . . . . . . . .  61
     9.21. CBOR Tags Registry  . . . . . . . . . . . . . . . . . . .  61
     9.22. TLSA Selectors Registry . . . . . . . . . . . . . . . . .  61
     9.23. EDHOC Authentication Credential Types Registry  . . . . .  62
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  62
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  62
     10.2.  Informative References . . . . . . . . . . . . . . . . .  64
   Appendix A.  C509 Certificate Examples  . . . . . . . . . . . . .  67
     A.1.  Example: RFC 7925 profiled X.509 Certificate  . . . . . .  68
     A.2.  Example: IEEE 802.1AR profiled X.509 Certificate  . . . .  73
     A.3.  Example: CAB Baseline ECDSA HTTPS X.509 Certificate . . .  77
     A.4.  Example: CAB Baseline RSA HTTPS X.509 Certificate . . . .  79
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  82
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  83
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  83

1.  Introduction

   One of the challenges with deploying a Public Key Infrastructure
   (PKI) for the Internet of Things (IoT) is the size and parsing of
   X.509 public key certificates [RFC5280], since those are not
   optimized for constrained environments [RFC7228].  Large certificate
   chains are also problematic in non-constrained protocols such as EAP-
   TLS [RFC9190] [RFC9191] where authenticators typically drop an EAP
   session after only 40–50 round-trips, QUIC [RFC9000] where the



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   latency increases significantly unless the server sends less than
   three times as many bytes as received prior to validating the client
   address, and RPKI [RFC6487] where a single certificate can be very
   large.  More compact certificate representations are therefore
   desirable in many use cases.  Due to the current PKI usage of DER
   encoded X.509 certificates, keeping compatibility with DER encoded
   X.509 is necessary at least for a transition period.  However, the
   use of a more compact encoding with the Concise Binary Object
   Representation (CBOR) [RFC8949] reduces the certificate size
   significantly which has known performance benefits in terms of
   decreased communication overhead, power consumption, latency,
   storage, etc.  The use of CBOR also reduces code complexity, code
   size, memory usage, and CPU usage.

   CBOR is a data format designed for small code size and small message
   size.  CBOR builds on the JSON data model but extends it by e.g.
   encoding binary data directly without base64 conversion.  In addition
   to the binary CBOR encoding, CBOR also has a diagnostic notation that
   is readable and editable by humans.  The Concise Data Definition
   Language (CDDL) [RFC8610] provides a way to express structures for
   protocol messages and APIs that use CBOR.  RFC 8610 also extends the
   diagnostic notation.

   CBOR data items are encoded to or decoded from byte strings using a
   type-length-value encoding scheme, where the three highest order bits
   of the initial byte contain information about the major type.  CBOR
   supports several different types of data items, in addition to
   integers (int, uint), simple values (e.g. null), byte strings (bstr),
   and text strings (tstr), CBOR also supports arrays [] of data items,
   maps {} of pairs of data items, and sequences of data items.  For a
   complete specification and examples, see [RFC8949], [RFC8610], and
   [RFC8742].  We recommend implementors to get used to CBOR by using
   the CBOR playground [CborMe].

   CAB Baseline Requirements [CAB-TLS], RFC 7925 [RFC7925], IEEE 802.1AR
   [IEEE-802.1AR], and CNSA 1.0 [RFC8603] specify certificate profiles
   which can be applied to certificate based authentication with, e.g.,
   TLS [RFC8446], QUIC [RFC9000], DTLS [RFC9147], COSE [RFC9052], EDHOC
   [RFC9528], or Compact TLS 1.3 [I-D.ietf-tls-ctls].  RFC 7925
   [RFC7925], RFC7925bis [I-D.ietf-uta-tls13-iot-profile], and IEEE
   802.1AR [IEEE-802.1AR] specifically target Internet of Things
   deployments.

   This document specifies a CBOR encoding of X.509 certificates based
   on [X.509-IoT].  The resulting certificates are called C509
   Certificates.  The CBOR encoding supports a large subset of RFC 5280
   and all certificates compatible with the RFC 7925, IEEE 802.1AR
   (DevID), CAB Baseline [CAB-TLS], [CAB-Code], RPKI [RFC6487], eUICC



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   [GSMA-eUICC] profiled X.509 certificates, and is designed to render a
   compact encoding of certificates used in constrained environments.
   When used to re-encode DER encoded X.509 certificates, the CBOR
   encoding can in many cases reduce the size of RFC 7925 profiled
   certificates with over 50% while also significantly reducing memory
   and code size compared to ASN.1.  C509 is not a general CBOR ecoding
   for Abstract Syntax Notation One (ASN.1) data structures.

   C509 is designed to be extensible to additional features of X.509,
   for example support for new algorithms, including new post-quantum
   algorithms, which can be registered in the IANA registry as they
   become specified, see Section 9.11.

   This document does not specify a certificate profile.  Two variants
   are defined using the same CBOR encoding and differing only in what
   is being signed:

   1.  An invertible CBOR re-encoding of DER encoded X.509 certificates
       [RFC5280], which can be reversed to obtain the original DER
       encoded X.509 certificate.

   2.  Natively signed C509 certificates, where the signature is
       calculated over the CBOR encoding instead of over the DER
       encoding as in 1.  This removes the need for ASN.1 and DER
       parsing and the associated complexity but they are not backwards
       compatible with implementations requiring DER encoded X.509.

   Natively signed C509 certificates can be applied in devices that are
   only required to authenticate to natively signed C509 certificate
   compatible servers, which is not a major restriction for many IoT
   deployments where the parties issuing and verifying certificates can
   be a restricted ecosystem.

   This document also specifies C509 Certificate Requests, see
   Section 4; COSE headers for use of the C509 certificates with COSE,
   see Section 9.13; and a TLS certificate type for use of the C509
   certificates with TLS and QUIC (with or without additional TLS
   certificate compression), see Section 9.20, and a C509 file format.

2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.





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   This specification makes use of the terminology in [RFC2986],
   [RFC5280], [RFC7228], [RFC8610], and [RFC8949].  When referring to
   CBOR, this specification always refers to Deterministically Encoded
   CBOR as specified in Sections 4.2.1 and 4.2.2 of [RFC8949].

3.  C509 Certificate

   This section specifies the content and encoding for C509
   certificates, with the overall objective to produce a very compact
   representation supporting large parts of [RFC5280], and everything in
   [RFC7925], [IEEE-802.1AR], RPKI [RFC6487], GSMA eUICC [GSMA-eUICC],
   and CAB Baseline [CAB-TLS] [CAB-Code].  In the CBOR encoding, static
   fields are elided, elliptic curve points and time values are
   compressed, OID are replaced with short integers or complemented with
   CBOR OID encoding [RFC9090], and redundant encoding is removed.
   Combining these different components reduces the certificate size
   significantly, which is not possible with general purpose compression
   algorithms, see Figure 6.

   The C509 certificate can be either a CBOR re-encoding of a DER
   encoded X.509 certificate, in which case the signature is calculated
   on the DER encoded ASN.1 data in the X.509 certificate, or a natively
   signed C509 certificate, in which case the signature is calculated
   directly on the CBOR encoded data.  In both cases the certificate
   content is adhering to the restrictions given by [RFC5280].  The re-
   encoding is known to work with DER encoded certificates but might
   work with other canonical encodings.  The re-encoding does not work
   for BER encoded certificates.

   In the encoding described below, the order of elements in arrays are
   always encoded in the same order as the elements or the corresponding
   SEQUENCE or SET in the DER encoding.

3.1.  Message Fields

   The X.509 fields and their CBOR encodings are described in this
   section, and used in the definition of C509 certificates, see
   Figure 1.

   The following Concise Data Definition Language (CDDL) defines the
   CBOR array C509Certificate and the CBOR sequence [RFC8742]
   TBSCertificate.  The member names therefore only have documentary
   value.  Applications not requiring a CBOR item MAY represent C509
   certificates with the CBOR sequence ~C509Certificate (unwrapped
   C509Certificate).  Examples are given in the appendices, e.g.
   Appendix A.1.





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   C509Certificate = [
      TBSCertificate,
      issuerSignatureValue : any,
   ]

   ; The elements of the following group are used in a CBOR Sequence:
   TBSCertificate = (
      c509CertificateType: int,
      certificateSerialNumber: CertificateSerialNumber,
      issuerSignatureAlgorithm: AlgorithmIdentifier,
      issuer: Name / null,
      validityNotBefore: ~time,
      validityNotAfter: ~time / null,
      subject: Name,
      subjectPublicKeyAlgorithm: AlgorithmIdentifier,
      subjectPublicKey: NonNull,
      extensions: Extensions,
   )

   CertificateSerialNumber = ~biguint

   Name = [ * Attribute ] / SpecialText

   Attribute = (( attributeType: int, attributeValue: SpecialText ) //
                ( attributeType: ~oid, attributeValue: bytes ))

   AlgorithmIdentifier = int / ~oid /
                       [ algorithm: ~oid, parameters: bytes ]

   Extensions = [ * Extension ] / int

   Extension = (( extensionID: int, extensionValue: NonNull ) //
                ( extensionID: ~oid, ? critical: true,
                 extensionValue: bytes ))

   SpecialText = text / bytes / tag

   NonNull = any .ne null

   tag = #6

                    Figure 1: CDDL for C509Certificate.

   C509 certificates are defined in terms of DER encoded [RFC5280] X.509
   certificates as detailed in the following subsections.






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3.1.1.  version

   The 'version' field is encoded in the 'c509CertificateType' CBOR int.
   The field 'c509CertificateType' also indicates the type of the C509
   certificate.  Currently, the type can be a natively signed C509
   certificate following X.509 v3 (c509CertificateType = 2) or a CBOR
   re-encoded X.509 v3 DER certificate (c509CertificateType = 3), see
   Section 9.1.

3.1.2.  serialNumber

   The 'serialNumber' INTEGER value field is encoded as the unwrapped
   CBOR unsigned bignum (~biguint) 'certificateSerialNumber'.  Any
   leading 0x00 byte (to indicate that the number is not negative) is
   therefore omitted.

3.1.3.  signature

   The 'signature' field, containing the signature algorithm including
   parameters, is encoded as a CBOR int (see Section 9.11) or as an
   array with an unwrapped CBOR OID tag [RFC9090] optionally followed by
   the parameters encoded as a CBOR byte string.

3.1.4.  issuer

   In the general case, the sequence of 'Attribute' is encoded as a CBOR
   array consisting of Attribute elements.  RelativeDistinguishedName
   with more than one AttributeTypeAndValue is not supported.  Each
   Attribute is CBOR encoded as (type, value) either as a (int,
   SpecialText) pair, or a (~oid, bytes) tuple.

   In the former case, the absolute value of the int encodes the
   attribute type (see Figure 10) and the sign is used to represent the
   character string type in the X.509 certificate; positive for
   utf8String, negative for printableString.  The attribute value for
   emailAddress and domainComponent are always of type IA5String (see
   [RFC5280]), and is for this reason unambiguously represented using a
   non-negative int.  In CBOR all text strings are UTF-8 encoded and in
   natively signed C509 certificates all CBOR ints SHALL be non-
   negative.  Text strings SHALL still adhere to any X.509 restrictions,
   i.e., serialNumber SHALL only contain the 74-character subset of
   ASCII allowed by printableString and countryName SHALL have length 2.
   CBOR encoding is allowed for IA5String (if this is the only allowed
   type, e.g. emailAddress), printableString and utf8String, whereas the
   string types teletexString, universalString, and bmpString are not
   supported.

   The text strings are further optimized as follows:



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   *  If the text string has an even length ≥ 2 and contains only the
      symbols '0'–'9' or 'a'–'f', it is encoded as a CBOR byte string.

   *  If the text string contains an EUI-64 of the form "HH-HH-HH-HH-HH-
      HH-HH-HH" where each 'H' is one of the symbols '0'-'9' or 'A'-'F'
      it is encoded as a CBOR tagged MAC address using the CBOR tag 48,
      see Section 2.4 of [RFC9542].  If of the form "HH-HH-HH-FF-FE-HH-
      HH-HH", it is encoded as a 48-bit MAC address, otherwise as a
      64-bit MAC address.  See example in Appendix A.1.

   *  Otherwise it is encoded as a CBOR text string.

   The final encoding of the extension value may therefore be text,
   bytes, or tag, i.e. SpecialText.  If Name contains a single 'common
   name' attribute with attributeType = +1 it is for compactness encoded
   as just the SpecialText containing the single attribute value.

   In natively signed C509 certificates, bytes and tag 48 does not
   correspond to any predefined text string encoding and may also be
   used for other attribute types such as macAddress.

   If the 'issuer' field is identical to the 'subject' field, e.g. in
   case of self-signed certificates, then the 'issuer' field MUST be
   encoded as CBOR null.

3.1.5.  validity

   The 'notBefore' and 'notAfter' fields are encoded as unwrapped CBOR
   epoch-based date/time (~time) where the tag content is an unsigned
   integer.  In POSIX time, leap seconds are ignored, with a leap second
   having the same POSIX time as the second before it.  Compression of
   X.509 certificates with the time 23:59:60 UTC is therefore not
   supported.  Note that RFC 5280 mandates encoding of dates through the
   year 2049 as UTCTime, and later dates as GeneralizedTime.  The value
   "99991231235959Z" (no expiration date) is encoded as CBOR null.

3.1.6.  subject

   The 'subject' field is encoded exactly like issuer, except that CBOR
   null is not a valid value.

3.1.7.  subjectPublicKeyInfo

   The 'AlgorithmIdentifier' field including parameters is encoded as
   the CBOR int 'subjectPublicKeyAlgorithm' (see Section 9.12) or as an
   array with an unwrapped CBOR OID tag [RFC9090] optionally followed by
   the parameters encoded as a CBOR byte string.




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   In general, the 'subjectPublicKey' BIT STRING value field is encoded
   as a CBOR byte string, but may be encoded as a CBOR item of any type
   except null.  This specification assumes the BIT STRING has zero
   unused bits, and the unused bits byte is omitted.  For rsaEncryption
   and id-ecPublicKey, the encoding of subjectPublicKey is further
   optimized as described in Section 3.2.

3.1.8.  issuerUniqueID

   Not supported.

3.1.9.  subjectUniqueID

   Not supported.

3.1.10.  extensions

   The 'extensions' field is encoded either as a CBOR array or as a CBOR
   int.  An omitted 'extensions' field is encoded as an empty CBOR
   array.

   Each 'extensionID' in the CBOR array is encoded either as a CBOR int
   (see Section 9.5) or as an unwrapped CBOR OID tag [RFC9090].

   *  If 'extensionID' is encoded as a CBOR int, it is followed by a
      CBOR item of any type except null, and the sign of the int is used
      to encode if the extension is critical: Critical extensions are
      encoded with a negative sign and non-critical extensions are
      encoded with a positive sign.  If the CBOR array contains exactly
      two ints and the absolute value of the first int is 2
      (corresponding to keyUsage, see Section 3.3), the CBOR array is
      omitted and the extensions is encoded as a single CBOR int with
      the absolute value of the second int and the sign of the first
      int.

   *  If extensionID is encoded as an unwrapped CBOR OID tag, then it is
      followed by an optional CBOR true 'critical', and the DER-encoded
      value of the extnValue.  The presence of the true value in the
      array indicates that the extension is critical; its absence means
      the extension is non-critical (see Figure 1).  The extnValue OCTET
      STRING value field is encoded as the CBOR byte string
      'extensionValue'.

   The currently defined extension values for which there is CBOR int
   encoded 'extensionID' is specified in Section 3.3.  The extensions
   mandated to be supported by [RFC7925] and [IEEE-802.1AR] are given
   special treatment.




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   More details about extensions in Section 3.3.

3.1.11.  signatureAlgorithm

   The 'signatureAlgorithm' field is always the same as the 'signature'
   field and therefore omitted from the CBOR encoding.

3.1.12.  signatureValue

   In general, the 'signatureValue' BIT STRING value field is encoded as
   the CBOR byte string issuerSignatureValue.  This specification
   assumes the BIT STRING has zero unused bits, and the unused bits byte
   is omitted.  For natively signed C509 certificates the signatureValue
   is calculated over the CBOR sequence TBSCertificate.  For ECDSA, the
   encoding of issuerSignatureValue is further optimized as described in
   Section 3.2

3.2.  Encoding of subjectPublicKey and issuerSignatureValue

3.2.1.  Encoding of subjectPublicKey

   For RSA public keys (rsaEncryption), the SEQUENCE and INTEGER type
   and length fields are omitted, and the two INTEGER value fields
   (modulus, exponent) are encoded as an array of two unwrapped CBOR
   unsigned bignum (~biguint), i.e. [ modulus : ~biguint, exponent :
   ~biguint ].  If the exponent is 65537, the array and the exponent is
   omitted and subjectPublicKey consist of only the modulus encoded as
   an unwrapped CBOR unsigned bignum (~biguint).

   For elliptic curve public keys in Weierstraß form (id-ecPublicKey),
   keys may be point compressed as defined in Section 2.3.3 of [SECG].
   Native C509 certificates with Weierstraß form keys use the octets
   0x02, 0x03, and 0x04 as defined in [SECG].  If a DER encoded
   certificate with an uncompressed public key of type id-ecPublicKey is
   CBOR encoded with point compression, the octets 0xfe and 0xfd are
   used instead of 0x02 and 0x03 in the CBOR encoding to represent even
   and odd y-coordinate, respectively.

3.2.2.  Encoding of issuerSignatureValue

   For ECDSA signatures, the SEQUENCE and INTEGER type and length fields
   as well as the any leading 0x00 byte (to indicate that the number is
   not negative) are omitted.  If the two INTEGER value fields have
   different lengths, the shorter INTEGER value field is padded with
   zeroes so that the two fields have the same length.  The resulting
   byte string is encoded as a CBOR byte string.





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3.3.  Encoding of Extensions

   The 'extensions' field is encoded as specified in Section 3.1.10 with
   further details provided in this section.

   For some extensions, the CBOR int encoded extensionID is only
   supported for commonly used values of the extension.  In case of
   extension values for which the CBOR int encoded extensionID is not
   supported, the extension MUST be encoded using the unwrapped CBOR OID
   tag encoded extensionID.

   A note on extensionID naming: in existing OID databases most IDs can
   be found in versions with and without an 'id-pe' or 'id-ce' prefix.
   We have excluded the prefix for the commonly used extensions defined
   in [RFC5280] and included them for extensions defined elsewhere.

   CBOR encoding of the following extension values is fully supported:

   *  Subject Key Identifier (subjectKeyIdentifier).  In natively signed
      certificates, KeyIdentifier SHOULD be composed of the leftmost
      160-bits of the SHA-256 hash of the CBOR encoded subjectPublicKey.
      Other methods of generating unique numbers can be used.  The
      extensionValue is encoded as follows:

      KeyIdentifier = bytes
      SubjectKeyIdentifier = KeyIdentifier

   *  Key Usage (keyUsage).  The 'KeyUsage' BIT STRING is interpreted as
      an unsigned integer in network byte order and encoded as a CBOR
      int.  See Section 3.1.10 for special encoding in case keyUsage is
      the only extension present.

      KeyUsage = int

   *  Policy Mappings (policyMappings). extensionValue is encoded as
      follows:

      PolicyMappings = [
        + (issuerDomainPolicy: ~oid, subjectDomainPolicy: ~oid)
      ]

   *  Basic Constraints (basicConstraints).  If 'cA' = false then
      extensionValue = -2, if 'cA' = true and 'pathLenConstraint' is not
      present then extensionValue = -1, and if 'cA' = true and
      'pathLenConstraint' is present then extensionValue =
      pathLenConstraint.

      BasicConstraints = int



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   *  Policy Constraints (policyConstraints). extensionValue is encoded
      as follows:

      PolicyConstraints = [
        requireExplicitPolicy: uint / null,
        inhibitPolicyMapping: uint / null,
      ]

   *  Extended Key Usage (extKeyUsage). extensionValue is encoded as an
      array of CBOR ints (see Section 9.9), or unwrapped CBOR OID tags
      [RFC9090], where each int or OID encodes a key usage purpose.  If
      the array contains a single KeyPurposeId, the array is omitted.

      KeyPurposeId = int / ~oid
      ExtKeyUsageSyntax = [ 2* KeyPurposeId ] / KeyPurposeId

   *  Inhibit anyPolicy (inhibitAnyPolicy). extensionValue is encoded as
      follows:

      InhibitAnyPolicy = uint

   CBOR encoding of the following extension values are partly supported:

   *  Subject Alternative Name (subjectAltName).  If the subject
      alternative name only contains general names registered in
      Section 9.10 the extension value can be CBOR encoded.
      extensionValue is encoded as an array of (int, any) pairs where
      each pair encodes a general name (see Section 9.10).  If
      subjectAltName contains exactly one dNSName, the array and the int
      are omitted and extensionValue is the dNSName encoded as a CBOR
      text string.  In addition to the general names defined in
      [RFC5280], the hardwareModuleName type of otherName has been given
      its own int due to its mandatory use in IEEE 802.1AR.  When
      'otherName + hardwareModuleName' is used, then [ ~oid, bytes ] is
      used to contain the pair ( hwType, hwSerialNum ) directly as
      specified in [RFC4108].  Only the general names in Section 9.10
      are supported.

      GeneralName = ( GeneralNameType : int, GeneralNameValue : any )
      GeneralNames = [ + GeneralName ]
      SubjectAltName = GeneralNames / text

   *  Issuer Alternative Name (issuerAltName). extensionValue is encoded
      exactly like subjectAltName.

      IssuerAltName  = GeneralNames / text





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   *  CRL Distribution Points (cRLDistributionPoints).  If the CRL
      Distribution Points is a sequence of DistributionPointName, where
      each DistributionPointName only contains
      uniformResourceIdentifiers, the extension value can be CBOR
      encoded. extensionValue is encoded as follows:

      DistributionPointName = [ 2* text ] / text
      CRLDistributionPoints = [ + DistributionPointName ]

   *  Freshest CRL (freshestCRL). extensionValue is encoded exactly like
      cRLDistributionPoints.

      FreshestCRL = CRLDistributionPoints

   *  Authority Information Access (authorityInfoAccess).  If all the
      GeneralNames in authorityInfoAccess are of type
      uniformResourceIdentifier, the extension value can be CBOR
      encoded.  Each accessMethod is encoded as a CBOR int (see
      Section 9.8) or an unwrapped CBOR OID tag [RFC9090].  The
      uniformResourceIdentifiers are encoded as CBOR text strings.

      AccessDescription = ( accessMethod: int / ~oid , uri: text )
      AuthorityInfoAccessSyntax = [ + AccessDescription ]

   *  Subject Information Access (subjectInfoAccess).  Encoded exactly
      like authorityInfoAccess.

      SubjectInfoAccessSyntax = AuthorityInfoAccessSyntax

   *  Authority Key Identifier (authorityKeyIdentifier).  If the
      authority key identifier contains all of keyIdentifier,
      certIssuer, and certSerialNumberm or if only keyIdentifier is
      present the extension value can be CBOR encoded.  If all three are
      present a CBOR array is used, if only keyIdentifier is present,
      the array is omitted:

      KeyIdentifierArray = [
        keyIdentifier: KeyIdentifier,
        authorityCertIssuer: GeneralNames,
        authorityCertSerialNumber: CertificateSerialNumber
      ]
      AuthorityKeyIdentifier = KeyIdentifierArray / KeyIdentifier

   *  Certificate Policies (certificatePolicies).  If noticeRef is not
      used and any explicitText are encoded as UTF8String, the extension
      value can be CBOR encoded.  OIDs registered in Section 9.6 are
      encoded as an int.  The policyQualifierId is encoded as an CBOR
      int (see Section 9.7) or an unwrapped CBOR OID tag [RFC9090].



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      PolicyIdentifier = int / ~oid
      PolicyQualifierInfo = (
        policyQualifierId: int / ~oid,
        qualifier: text,
      )
      CertificatePolicies = [
        + ( PolicyIdentifier, ? [ + PolicyQualifierInfo ] )
      ]

   *  Name Constraints (nameConstraints).  If the name constraints only
      contain general names registered in Section 9.10 the extension
      value can be CBOR encoded.  C509 uses the same additions and
      restrictions as defined in Section 4.2.1.10 of [RFC5280].  Note
      that the minimum and maximum fields are not used and therefore
      omitted.

      GeneralSubtrees = [ + GeneralName ]
      NameConstraints = [
        permittedSubtrees: GeneralSubtrees / null,
        excludedSubtrees: GeneralSubtrees / null,
      ]

   *  Subject Directory Attributes (subjectDirectoryAttributes).
      Encoded as attributes in issuer and subject with the difference
      that there can be more than one attributeValue.

         Attributes = (( attributeType: int,
                         attributeValue: [+ SpecialText] ) //
                       ( attributeType: ~oid, attributeValue: [+ bytes] ))
         SubjectDirectoryAttributes = [+Attributes]

   *  AS Resources (id-pe-autonomousSysIds).  If rdi is not present, the
      extension value can be CBOR encoded.  Each ASId is encoded as an
      uint.  With the exception of the first ASId, the ASid is encoded
      as the difference to the previous ASid.

      ASIdOrRange = uint / [min:uint, max:uint]
      ASIdentifiers = [ + ASIdOrRange ] / null

   *  AS Resources v2 (id-pe-autonomousSysIds-v2).  Encoded exactly like
      autonomousSysIds.

   *  IP Resources (id-pe-ipAddrBlocks).  If rdi and SAFI is not
      present, the extension value can be CBOR encoded.  Each
      AddressPrefix is encoded as a CBOR bytes string (without the
      unused bits octet) followed by the number of unused bits encoded
      as a CBOR uint.  Each AddressRange is encoded as an array of two
      CBOR byte strings.  The unused bits for min and max are omitted,



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      but the unused bits in max IPAddress is set to ones.  With the
      exception of the first Address, if the byte string has the same
      length as the previous Address, the Address is encoded as an uint
      with the the difference to the previous Address.  It should be
      noted that using address differences for compactness prevents
      encoding an address range larger than 2^64 - 1 corresponding to
      the CBOR integer max value.

      Address = bytes
      AddressPrefix = (Address, unusedBits: uint)
      AddressRange = [min: Address, max: Address]
      IPAddressOrRange = AddressPrefix / AddressRange
      IPAddressChoice = [ + IPAddressOrRange ] / null
      IPAddressFamily = (AFI: uint, IPAddressChoice)
      IPAddrBlocks = [ + IPAddressFamily ]

   *  IP Resources v2 (id-pe-ipAddrBlocks-v2).  Encoded exactly like id-
      pe-ipAddrBlocks.

   *  Signed Certificate Timestamp (Certificate Transparency).  If all
      the SCTs are version v1 [RFC6962], and there are no SCT
      extensions, the extension value can be CBOR encoded.  Other
      versions of SCT are out of scope for this document.  LogIDs are
      encoded as CBOR byte strings, the timestamp is encoded as a CBOR
      int (milliseconds since validityNotBefore), and the signature is
      encoded with an (AlgorithmIdentifier, any) pair in the same way as
      issuerSignatureAlgorithm and issuerSignatureValue.

      SignedCertificateTimestamp = (
        logID: bytes,
        timestamp: int,
        sigAlg: AlgorithmIdentifier,
        sigValue: any,
      )
      SignedCertificateTimestamps = [ + SignedCertificateTimestamp ]

   *  OCSP No Check (id-pkix-ocsp-nocheck).  If the extension value is
      NULL it can be CBOR encoded.  The CBOR encoded extensionValue is
      the empty string h''.

   *  Precertificate Signing Certificate.  The CBOR encoded
      extensionValue is the empty string h''.

   *  TLS Features (id-pe-tlsfeature).  The extensionValue is encoded as
      an array of integers, where each integer represents a TLS
      extension.

      TLSFeatures = [* feature: uint]



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3.3.1.  Example Encoding of Extensions

   The examples below use values from Section 9.5, Section 9.9, and
   Section 9.10:

   *  A critical basicConstraints ('cA' = true) without
      pathLenConstraint is encoded as the two CBOR ints -4, -1.

   *  A non-critical keyUsage with digitalSignature (0), nonRepudiation
      (1), keyEncipherment (2) and keyAgreement (4) asserted is encoded
      as the two CBOR ints 2, 23 (2^0 + 2^1 + 2^2 + 2^4 = 23).

   *  A non-critical extKeyUsage containing id-kp-codeSigning and id-kp-
      OCSPSigning is encoded as the CBOR int 8 followed by the CBOR
      array [ 3, 9 ].

   *  A non-critical subjectAltName containing only the dNSName
      example.com is encoded as the CBOR int 3 followed by the CBOR text
      string "example.com".

   Thus, the extension field of a certificate containing all of the
   above extensions in the given order would be encoded as the CBOR
   array [ -4, -1, 2, 23, 8, [ 3, 9 ], 3, "example.com" ].

3.4.  COSE Header Parameters

   The formatting and processing for c5b, c5c, c5t, and c5u, defined in
   Table 1 below, are similar to x5bag, x5chain, x5t, x5u defined in
   [RFC9360] except that the certificates are C509 instead of DER
   encoded X.509 and uses a COSE_C509 structure instead of COSE_X509.
   c5u provides an alternative way to identify an untrusted certificate
   chain by reference with a URI [RFC3986], encoded as a CBOR text
   string.  The content is a COSE_C509 item served with the application/
   cose-c509-cert media type ("usage" = "chain"), see Section 9.14, with
   corresponding CoAP Content-Format defined in Section 9.19.  A stored
   file format is defined in [RFC9277], with "magic number" TBD8
   composed of the reserved CBOR tag 55799 concatenated with the CBOR
   tag calculated from the CoAP Content-Format value.

   The COSE_C509 structure used in c5b, c5c, and c5u is defined as:

   COSE_C509 = C509CertData / [ 2* C509CertData ]
   C509CertData = bstr .cborseq C509Certificate

   C509CertData thus includes the unwrapped CBOR sequence,
   ~C509Certificate, see Appendix A.1.5 for an example.





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   The value type of c5t is the COSE_CertHash structure defined in
   [RFC9360], which contains the hash value of the C509 certificate
   calculated over ~C509Certificate.  Thus C509CertData contains all
   data necessary to calculate the thumbprint c5t.

   c5u provides an alternative way to identify an untrusted certificate
   bag/chain by reference with a URI.

   The COSE_C509 item has media type application/cose-c509-cert, see
   Section 9.14, with corresponding CoAP Content-Format defined in
   Section 9.19.  A stored file format is defined in [RFC9277], with
   "magic number" TBD8 composed of the reserved CBOR tag 55799
   concatenated with the CBOR tag calculated from the CoAP Content-
   Format value.

   As the contents of c5b, c5c, c5t, and c5u are untrusted input, the
   header parameters can be in either the protected or unprotected
   header bucket.  The trust mechanism MUST process any certificates in
   the c5b, c5c, and c5u parameters as untrusted input.  The presence of
   a self-signed certificate in the parameter MUST NOT cause the update
   of the set of trust anchors without some out-of-band confirmation.

      +======+=======+===============+=============================+
      | Name | Label | Value Type    | Description                 |
      +======+=======+===============+=============================+
      |  c5b | TBD1  | COSE_C509     | An unordered bag of C509    |
      |      |       |               | certificates                |
      +------+-------+---------------+-----------------------------+
      |  c5c | TBD2  | COSE_C509     | An ordered chain of C509    |
      |      |       |               | certificates                |
      +------+-------+---------------+-----------------------------+
      |  c5t | TBD3  | COSE_CertHash | Hash of a ~C509Certificate  |
      +------+-------+---------------+-----------------------------+
      |  c5u | TBD4  | uri           | URI pointing to a COSE_C509 |
      |      |       |               | containing an ordered chain |
      |      |       |               | of certificates             |
      +------+-------+---------------+-----------------------------+

                     Table 1: COSE Header Parameters

   Note that certificates can also be identified with a 'kid' header
   parameter by storing 'kid' and the associated bag or chain in a
   dictionary.








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3.5.  Private Key Structures

   Certificate management also makes use of data structures including
   private keys, see e.g. [RFC7468].  This section defines the following
   CBOR encoded structures:

   C509PrivateKey = [
      C509PrivateKeyType: int,
      subjectPrivateKeyAlgorithm: AlgorithmIdentifier,
      subjectPrivateKey: any,
   ]

   The field 'C509PrivateKeyType' indicates the type of the C509 private
   key.  Different types of C509 Private Key Structures can be defined,
   see Section 9.3.  Currently, two types are defined.  When
   C509PrivateKeyType = 0, the subjectPrivateKey is the CBOR byte string
   encoding of the PrivateKey OCTET STRING value field defined in
   [RFC5958].  When C509PrivateKeyType = 1, the subjectPrivateKey is a
   COSE_KEY structure containing a private key as defined in [RFC9052].
   Note that COSE_KEY might not be possible to use with all algorithms
   that have a C509 AlgorithmIdentifier defined.

   The C509PrivateKey item is served with the application/cose-
   c509-privkey media type, see Section 9.16, with corresponding CoAP
   Content-Format defined in Section 9.19.  A stored file format is
   defined in [RFC9277], with "magic number" TBD12 composed of the
   reserved CBOR tag 55799 concatenated with the CBOR tag calculated
   from the CoAP Content-Format value.

   C509PEM = [
      C509PrivateKey,
      COSE_C509 / null,
   ]

   The C509PEM item is served with the application/cose-c509-pem media
   type, see Section 9.17, with corresponding CoAP Content-Format
   defined in Section 9.19.  A stored file format is defined in
   [RFC9277], with "magic number" TBD13 composed of the reserved CBOR
   tag 55799 concatenated with the CBOR tag calculated from the CoAP
   Content-Format value.

3.6.  Deterministic Encoding

   In some use cases it is desirable to be able to specify a unique C509
   representation of a given X.509 certificate.






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   While this specification requires the use of Deterministically
   Encoded CBOR (see Section 2), it is still possible to represent
   certain X.509 certificate fields in different ways.  This is a
   consequence of the extensibility of the C509 format where new
   encodings can be defined, for example to optimize extensions for
   which no special CBOR encoding have been previously defined.

   Where there is support for a specific and a generic CBOR encoding,
   the specific CBOR encoding MUST be used.  For example, when there is
   support for specific CBOR encoding of an extension, as specified in
   Section 3.3 and the C509 Extensions Registry, it MUST be used.  In
   particular, when there is support for a specific otherName encoding
   (negative integer value in C509 General Names Registry) it MUST be
   used.

   Native C509 certificates MUST only use specific CBOR encoded fields.
   However, when decoding a non-native C509 certificates, the decoder
   may need to support, for example, (extensionID:~oid,
   extensionValue:bstr)-encoding of an extension for which there is an
   (extensionID:int, extensionValue:any)-encoding.  One reason being
   that the certificate was issued before the specific CBOR extension
   was registered.

4.  C509 Certificate (Signing) Request

   This section defines the format of a C509 Certificate Request, also
   known as a C509 Certificate Signing Request (CSR), based on and
   compatible with RFC 2986 [RFC2986], and reusing the formatting of
   C509 certificates defined in Section 3.

   The CDDL for the C509 Certificate Request is shown in Figure 2.  The
   fields have the same encoding as the corresponding fields of the C509
   Certificate, see Section 3.1.

   C509CertificateRequest = [
      TBSCertificateRequest,
      subjectSignatureValue: any,
   ]

   ; The elements of the following group are used in a CBOR Sequence:
   TBSCertificateRequest = (
      c509CertificateRequestType: int,
      subjectSignatureAlgorithm: AlgorithmIdentifier,
      subject: Name,
      subjectPublicKeyAlgorithm: AlgorithmIdentifier,
      subjectPublicKey: NonNull,
      extensionsRequest: Extensions,
   )



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                 Figure 2: CDDL for C509CertificateRequest.

   After verifying the subjectSignatureValue, the CA MAY transform the
   C509CertificateRequest into a [RFC2986] CertificationRequestInfo for
   compatibility with existing procedures and code.

   The media type of C509CertificateRequest is application/cose-
   c509-pkcs10, see Section 9.15, with corresponding CoAP Content-Format
   defined in Section 9.19.  The "magic number" TBD9 is composed of the
   reserved CBOR tag 55799 concatenated with the CBOR tag calculated
   from the CoAP Content-Format value, see [RFC9277].

4.1.  Certificate Request Types

   Different types of C509 Certificate Requests are defined, see
   Section 9.2, all using the same CBOR encoding and differing only in
   what is being signed and what type of C509 certificate is being
   requested:

   *  The C509 Certificate Request can either be an invertible CBOR re-
      encoding of a DER encoded RFC 2986 certification request, or it
      can be natively signed where the signature is calculated over the
      CBOR encoding instead of the DER encoding.

   *  The requested C509 certificate in the C509 Certificate Request can
      either be of type 2 or of type 3, see Section 9.1.

   Combining these options enables the four instances of
   c509CertificateRequestType defined in Section 9.2 and illustrated in
   Figure 3.

    +-------------------------+---------------------------------------+
    |                         |             Signed object             |
    +-------------------------+---------------------------------------+
    |                         | CBOR encoded C509 | DER encoded C509  |
    |                         |    Certificate    |    Certificate    |
    | Requested certificate   |      Request      |      Request      |
    +=========================+===================+===================+
    | c509CertificateType = 2 |         0         |           1       |
    +-------------------------+-------------------+-------------------+
    | c509CertificateType = 3 |         2         |           3       |
    +-------------------------+-------------------+-------------------+

          Figure 3: C509 Certificate Request Types 0, 1, 2 and 3.

   An implementation MAY only support c509CertificateRequestType = 0.
   The most common variants are expected to be:




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   *  c509CertificateRequestType = 0.  This type indicates that the C509
      Certificate Request is natively signed, and that the requested
      certificate format has c509CertificateType = 2.  This encoding
      removes the need for ASN.1 and DER parsing and re-encoding in the
      requesting party.

   *  c509CertificateRequestType = 3.  This type indicates that the C509
      Certificate Request is CBOR re-encoded RFC 2986 certification
      requests, and that the requested certificate format has
      c509CertificateType = 3.  This encoding is backwards compatible
      with legacy RFC 2986 certification requests and X.509
      certificates, but enables a reduced transport overhead.

4.2.  Subject Signature Algorithm

   subjectSignatureAlgorithm can be a signature algorithm or a non-
   signature proof-of-possession algorithm, e.g., as defined in
   [RFC6955].  In the case of [RFC6955], the signature is replaced by a
   MAC and requires a public Diffie-Hellman key of the verifier
   distributed out-of-band.  Both signature algorithms and non-signature
   proof-of-possession algorithms are listed in the C509 Signature
   Algorithms Registry, see Section 9.11.  Note that a key agreement key
   pair may be used with a signature algorithm in a certificate request,
   see Appendix A.1.3.

4.3.  Certificate Request Attributes

   Section 5.4 of [RFC2985] specifies two attribute types that may be
   included in the certificate request: extension request and challenge
   password.

4.3.1.  Extensions Request

   The extensionRequest field is used to carry information about
   certificate extensions the entity requesting certification wishes to
   be included in the certificate, encoded as Extensions in Section 3.1.
   An empty CBOR array indicate no extensions.

4.3.2.  Challenge Password

   Other certificate request attributes are included using the
   Extensions structure and the extensionRequest field.  The only other
   certificate request attribute specified in this document is
   challengePassword, listed in the C509 Extensions Registry, see
   Figure 11.  The extensionValue is encoded as follows:

   challengePassword = SpecialText




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   In natively signed requests (types 0 and 2), a positive extensionID
   is used.  In CBOR re-encoding of a DER encoded request (types 1 and
   3), the sign of extensionID of challengePassword indicates the string
   type in the DER encoded challengePassword (instead of the
   criticalness in extensions): positive for utf8String and negative for
   printableString.  The same text string encoding optimizations applies
   as in Section 3.1.4.

4.4.  Certificate Request Template

   Enrollment over Secure Transport (EST, [RFC7030]) defines, and
   [I-D.ietf-lamps-rfc7030-csrattrs] clarifies, how an EST server can
   specify what it expects the EST client to include in a subsequent
   Certificate Signing Request (CSR).  Alternatively to the unstructured
   mechanism specified in [RFC7030], Appendix B of [RFC8295] describes
   an approach using a CSR template: In response to GET /csrattrs by the
   EST client, the EST server returns an entire CSR object with various
   fields filled out, and other fields waiting to be filled in by the
   EST client.

   For C509 we follow the approach of [RFC8295].  The
   C509CertificateRequestTemplate is based on TBSCertificateRequest of
   the C509CertificateRequest, see Figure 2, which excludes the
   subjectSignatureValue field from the template since that needs no
   further specification.

   The C509 Certificate Request Template is shown in Figure 4.
























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   C509CertificateRequestTemplate = [
      c509CertificateRequestType: int / null,
      subjectSignatureAlgorithm: AlgorithmIdentifier / null,
      subject: NameTemplate,
      subjectPublicKeyAlgorithm: AlgorithmIdentifier / null,
      subjectPublicKey: any,
      extensionsRequest: ExtensionsTemplate,
   ]

   NameTemplate = [ * AttributeTemplate ] / SpecialText

   AttributeTemplate = (( attributeType: int,
                          attributeValue: SpecialText / null ) //
                        ( attributeType: ~oid,
                          attributeValue: bytes / null ))

   ExtensionsTemplate = [ * ExtensionTemplate ] / int

   ExtensionTemplate = (( extensionID: int, extensionValue: any ) //
                        ( extensionID: ~oid, ? critical: true,
                          extensionValue: bytes / null ))

             Figure 4: CDDL for C509CertificateRequestTemplate.

   Except as specified in this section, the fields have the same
   encoding as the corresponding fields of the TBSCertificateRequest,
   see Figure 2.

   The presence of a non-null value in a C509CertificateRequestTemplate
   indicates that the EST server expects this value to be used in the
   certificate request by the EST client.  The presence of a null value
   in a C509CertificateRequestTemplate indicates that the EST server
   expects the EST client to replace it with a relevant value for that
   field.

5.  C509 Processing and Certificate Issuance

   It is straightforward to integrate the C509 format into legacy X.509
   processing during certificate issuance.  C509 processing can be
   performed as an isolated function of the CA, or as a separate
   function trusted by the CA.

   The Certificate Request format defined in Section 4 follows the
   PKCS#10 format to enable a direct mapping to the certification
   request information, see Section 4.1 of [RFC2986].






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   When a certificate request is received, the CA, or function trusted
   by the CA, needs to perform some limited C509 processing and verify
   the proof-of-possession corresponding to the public key, before
   normal certificate generation can take place.

   In the reverse direction, in case c509CertificateType = 3 was
   requested, a separate C509 processing function can perform the
   conversion from a generated X.509 certificate to C509 as a bump-in-
   the-wire.  In case c509CertificateType = 2 was requested, the C509
   processing needs to be performed before signing the certificate, in
   which case a tighter integration with the CA may be needed.

6.  Legacy Considerations

   C509 certificates can be deployed with legacy X.509 certificates and
   CA infrastructure.  An existing CA can continue to use its existing
   procedures and code for PKCS#10, and DER encoded X.509 and only
   implement C509 as a thin processing layer on top.  When receiving a
   C509 CSR, the CA transforms it into a DER encoded RFC 2986
   CertificationRequestInfo and use that with existing processes and
   code to produce an RFC 5280 DER encoded X.509 certificate.  The DER
   encoded X.509 is then transformed into a C509 certificate.  At any
   later point, the C509 certificate can be used to recreate the
   original X.509 data structure needed to verify the signature.

   For protocols like TLS/DTLS 1.2, where the handshake is sent
   unencrypted, the actual encoding and compression can be done at
   different locations depending on the deployment setting.  For
   example, the mapping between C509 certificate and standard X.509
   certificate can take place in a 6LoWPAN border gateway which allows
   the server side to stay unmodified.  This case gives the advantage of
   the low overhead of a C509 certificate over a constrained wireless
   links.  The conversion to X.509 within a constrained IoT device will
   incur a computational overhead, however, measured in energy this is
   likely to be negligible compared to the reduced communication
   overhead.

   For the setting with constrained server and server-only
   authentication, the server only needs to be provisioned with the C509
   certificate and does not perform the conversion to X.509.  This
   option is viable when client authentication can be asserted by other
   means.

   For protocols like IKEv2, TLS/DTLS 1.3, and EDHOC, where certificates
   are encrypted, the proposed encoding needs to be done fully end-to-
   end, through adding the encoding/decoding functionality to the
   server.




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7.  Expected Certificate Sizes

   The CBOR encoding of the sample certificate chains given in
   Appendix A results in the numbers shown in Figures 5 and 6.
   COSE_X509 is defined in [RFC9360] and COSE_C509 is defined in
   Section 9.13.  After RFC 7925 profiling, most duplicated information
   has been removed, and the remaining text strings are minimal in size.
   Therefore, the further size reduction reached with general
   compression mechanisms such as Brotli will be small, mainly
   corresponding to making the ASN.1 encoding more compact.  CBOR
   encoding can however significantly compress RFC 7925 profiled
   certificates.  For the example HTTPS certificate chains (www.ietf.org
   and tools.ietf.org) both C509 and Brotli perform well complementing
   each other.  C509 use dedicated information to compress individual
   certificates, while Brotli can compress duplicate information in the
   entire chain.  Note that C509 certificates of type 2 and 3 have the
   same size.  For Brotli [RFC7932], the Rust crate Brotli 3.3.0 was
   used with compression level 11 and window size 22.

     +---------------------------------------+-----------+-----------+
     |                                       | COSE_X509 | COSE_C509 |
     +---------------------------------------+-----------+-----------+
     | RFC 7925 profiled IoT Certificate (1) |       317 |       142 |
     +---------------------------------------+-----------+-----------+
     | ECDSA HTTPS Certificate Chain (2)     |      2193 |      1397 |
     +---------------------------------------+-----------+-----------+
     | RSA HTTPS Certificate Chain (4)       |      5175 |      3937 |
     +---------------------------------------+-----------+-----------+

      Figure 5: Comparing Sizes of Certificate Chains in COSE.  Number
                  of bytes (length of certificate chain).

   +-------------------+-------+----------------+------+---------------+
   |                   | X.509 | X.509 + Brotli | C509 | C509 + Brotli |
   +-------------------+-------+----------------+------+---------------+
   | RFC 7925 Cert (1) |   327 |            324 |  152 |           170 |
   +-------------------+-------+----------------+------+---------------+
   | RPKI Cert (1)     | 20991 |           9134 | 8663 |          5671 |
   +-------------------+-------+----------------+------+---------------+
   | HTTPS Chain (2)   |  2204 |           1455 | 1417 |          1066 |
   +-------------------+-------+----------------+------+---------------+
   | HTTPS Chain (4)   |  5190 |           3244 | 3961 |          2848 |
   +-------------------+-------+----------------+------+---------------+
   | HTTPS Bag (8)     | 11578 |           3979 | 8885 |          3522 |
   +-------------------+-------+----------------+------+---------------+






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     Figure 6: Comparing Sizes of Certificate Chains with TLS.  Number
        of bytes (length of certificate chain).  X.509 and C509 are
        Certificate messages.  X.509 + Brotli and C509 + Brotli are
                      CompressedCertificate messages.

8.  Security Considerations

   The CBOR profiling of X.509 certificates does not change the security
   assumptions needed when deploying standard X.509 certificates but
   decreases the number of fields transmitted, which reduces the risk
   for implementation errors.

   The use of natively signed C509 certificates removes the need for
   ASN.1 encoding, which is a rich source of security vulnerabilities.

   Conversion between the certificate formats can be made in constant
   time to reduce risk of information leakage through side channels.

   The mechanism in this draft does not reveal any additional
   information compared to X.509.  Because of difference in size, it
   will be possible to detect that this profile is used.  The gateway
   solution described in Section 6 requires unencrypted certificates and
   is not recommended.

9.  IANA Considerations

   This document creates several new registries under the new heading
   "CBOR Encoded X.509 (C509) Parameters".  For all items, the
   'Reference' field points to this document.

   The expert reviewers for the registries defined in this document are
   expected to ensure that the usage solves a valid use case that could
   not be solved better in a different way, that it is not going to
   duplicate one that is already registered, and that the registered
   point is likely to be used in deployments.  They are furthermore
   expected to check the clarity of purpose and use of the requested
   code points.  Experts should take into account the expected usage of
   entries when approving point assignment, and the length of the
   encoded value should be weighed against the number of code points
   left that encode to that size and how constrained the systems it will
   be used on are.  Values in the interval [-24, 23] have a 1-byte
   encodings, other values in the interval [-256, 255] have a 2-byte
   encodings, and the remaining values in the interval [-65536, 65535]
   have 3-byte encodings.







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9.1.  C509 Certificate Types Registry

   IANA has created a new registry titled "C509 Certificate Types" under
   the new heading "CBOR Encoded X.509 (C509) Parameters".  The columns
   of the registry are Value, Description, and Reference, where Value is
   an integer, and the other columns are text strings.  All columns are
   mandatory.  For values in the interval [-24, 23] the registration
   procedure is "IETF Review" and "Expert Review".  For all other values
   the registration procedure is "Expert Review".  The initial contents
   of the registry are:

   +-------+-----------------------------------------------------------+
   | Value | Description                                               |
   +=======+===========================================================+
   |     0 | Reserved                                                  |
   +-------+-----------------------------------------------------------+
   |     1 | Reserved                                                  |
   +-------+-----------------------------------------------------------+
   |     2 | Natively Signed C509 Certificate following X.509 v3       |
   +-------+-----------------------------------------------------------+
   |     3 | CBOR re-encoding of X.509 v3 Certificate                  |
   +-------+-----------------------------------------------------------+

                      Figure 7: C509 Certificate Types

9.2.  C509 Certificate Request Types Registry

   IANA has created a new registry titled "C509 Certificate Request
   Types" under the new heading "CBOR Encoded X.509 (C509) Parameters".
   The columns of the registry are Value, Description, and Reference,
   where Value is an integer, and the other columns are text strings.
   All columns are mandatory.  For values in the interval [-24, 23] the
   registration procedure is "IETF Review" and "Expert Review".  For all
   other values the registration procedure is "Expert Review".  The
   initial contents of the registry are:
















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   +-------+-----------------------------------------------------------+
   | Value | Description                                               |
   +=======+===========================================================+
   |     0 | Requested certificate is C509 Type 2.                     |
   |       | Natively Signed C509 Certificate Request.                 |
   +-------+-----------------------------------------------------------+
   |     1 | Requested certificate is C509 Type 2.                     |
   |       | CBOR re-encoding of RFC 2986 certification request.       |
   +-------+-----------------------------------------------------------+
   |     2 | Requested certificate is C509 Type 3.                     |
   |       | Natively Signed C509 Certificate Request.                 |
   +-------+-----------------------------------------------------------+
   |     3 | Requested certificate is C509 Type 3.                     |
   |       | CBOR re-encoding of RFC 2986 certification request.       |
   +-------+-----------------------------------------------------------+

                  Figure 8: C509 Certificate Request Types

9.3.  C509 Private Key Types

   IANA has created a new registry titled "C509 Private Key Types" under
   the new heading "CBOR Encoded X.509 (C509) Parameters".  The columns
   of the registry are Value, Comments, and subjectPrivateKey, and
   Reference, where Value is an integer, and the other columns are text
   strings.  All columns are mandatory.  For values in the interval
   [-24, 23] the registration procedure is "IETF Review" and "Expert
   Review".  For all other values the registration procedure is "Expert
   Review".  The initial contents of the registry are:

   +-------+-----------------------------------------------------------+
   | Value | Private Key Types                                         |
   +=======+===========================================================+
   |     0 | Comments:          Asymmetric Key Package (RFC 5958)      |
   |       | subjectPrivateKey: bytes                                  |
   +-------+-----------------------------------------------------------+
   |     1 | Comments:          COSE Key Object (RFC 9052)             |
   |       | subjectPrivateKey: COSE_Key                               |
   +-------+-----------------------------------------------------------+

                      Figure 9: C509 Private Key Types











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9.4.  C509 Attributes Registry

   IANA has created a new registry titled "C509 Attributes" under the
   new heading "CBOR Encoded X.509 (C509) Parameters".  The columns of
   the registry are Value, Name, Identifiers, OID, DER, Comments, and
   Reference, where Value is a non-negative integer, and the other
   columns are text strings.  The columns Name, OID, and DER are
   mandatory.  For values in the interval [0, 23] the registration
   procedure is "IETF Review" and "Expert Review".  Values ≥ 32768 are
   reserved for Private Use. For all other values the registration
   procedure is "Expert Review".  Name and Identifiers are informal
   descriptions.  The OID is given in dotted decimal representation.
   The DER column contains the hex string of the DER-encoded OID
   [X.690].

   The initial contents of the registry are:

   +-------+-----------------------------------------------------------+
   | Value | Attribute                                                 |
   +=======+===========================================================+
   |     0 | Name:            Email Address                            |
   |       | Identifiers:     emailAddress, e-mailAddress              |
   |       | OID:             1.2.840.113549.1.9.1                     |
   |       | DER:             06 09 2A 86 48 86 F7 0D 01 09 01         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     1 | Name:            Common Name                              |
   |       | Identifiers:     commonName, cn                           |
   |       | OID:             2.5.4.3                                  |
   |       | DER:             06 03 55 04 03                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     2 | Name:            Surname                                  |
   |       | Identifiers:     surname, sn                              |
   |       | OID:             2.5.4.4                                  |
   |       | DER:             06 03 55 04 04                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     3 | Name:            Serial Number                            |
   |       | Identifiers:     serialNumber                             |
   |       | OID:             2.5.4.5                                  |
   |       | DER:             06 03 55 04 05                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     4 | Name:            Country                                  |
   |       | Identifiers:     countryName, c                           |
   |       | OID:             2.5.4.6                                  |
   |       | DER:             06 03 55 04 06                           |



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   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     5 | Name:            Locality                                 |
   |       | Identifiers:     localityName, locality, l                |
   |       | OID:             2.5.4.7                                  |
   |       | DER:             06 03 55 04 07                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     6 | Name:            State or Province                        |
   |       | Identifiers:     stateOrProvinceName, st                  |
   |       | OID:             2.5.4.8                                  |
   |       | DER:             06 03 55 04 08                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     7 | Name:            Street Address                           |
   |       | Identifiers:     streetAddress, street                    |
   |       | OID:             2.5.4.9                                  |
   |       | DER:             06 03 55 04 09                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     8 | Name:            Organization                             |
   |       | Identifiers:     organizationName, o                      |
   |       | OID:             2.5.4.10                                 |
   |       | DER:             06 03 55 04 0A                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     9 | Name:            Organizational Unit                      |
   |       | Identifiers:     organizationalUnitName, ou               |
   |       | OID:             2.5.4.11                                 |
   |       | DER:             06 03 55 04 0B                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    10 | Name:            Title                                    |
   |       | Identifiers:     title                                    |
   |       | OID:             2.5.4.12                                 |
   |       | DER:             06 03 55 04 0C                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    11 | Name:            Business Category                        |
   |       | Identifiers:     businessCategory                         |
   |       | OID:             2.5.4.15                                 |
   |       | DER:             06 03 55 04 0F                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    12 | Name:            Postal Code                              |
   |       | Identifiers:     postalCode                               |
   |       | OID:             2.5.4.17                                 |
   |       | DER:             06 03 55 04 11                           |



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   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    13 | Name:            Given Name                               |
   |       | Identifiers:     givenName                                |
   |       | OID:             2.5.4.42                                 |
   |       | DER:             06 03 55 04 2A                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    14 | Name:            Initials                                 |
   |       | Identifiers:     initials                                 |
   |       | OID:             2.5.4.43                                 |
   |       | DER:             06 03 55 04 2B                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    15 | Name:            Generation Qualifier                     |
   |       | Identifiers:     generationQualifier                      |
   |       | OID:             2.5.4.44                                 |
   |       | DER:             06 03 55 04 2C                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    16 | Name:            DN Qualifier                             |
   |       | Identifiers:     dnQualifier                              |
   |       | OID:             2.5.4.46                                 |
   |       | DER:             06 03 55 04 2E                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    17 | Name:            Pseudonym                                |
   |       | Identifiers:     pseudonym                                |
   |       | OID:             2.5.4.65                                 |
   |       | DER:             06 03 55 04 41                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    18 | Name:            Organization Identifier                  |
   |       | Identifiers:     organizationIdentifier                   |
   |       | OID:             2.5.4.97                                 |
   |       | DER:             06 03 55 04 61                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    19 | Name:            Inc. Locality                            |
   |       | Identifiers:     jurisdictionOfIncorporationLocalityName  |
   |       | OID:             1.3.6.1.4.1.311.60.2.1.1                 |
   |       | DER:             06 0B 2B 06 01 04 01 82 37 3C 02 01 01   |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    20 | Name:            Inc. State or Province                   |
   |       | Identifiers:     jurisdictionOfIncorporation              |
   |       |                  StateOrProvinceName                      |
   |       | OID:             1.3.6.1.4.1.311.60.2.1.2                 |



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   |       | DER:             06 0B 2B 06 01 04 01 82 37 3C 02 01 02   |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    21 | Name:            Inc. Country                             |
   |       | Identifiers:     jurisdictionOfIncorporationCountryName   |
   |       | OID:             1.3.6.1.4.1.311.60.2.1.3                 |
   |       | DER:             06 0B 2B 06 01 04 01 82 37 3C 02 01 03   |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    22 | Name:            Domain Component                         |
   |       | Identifiers:     domainComponent, dc                      |
   |       | OID:             0.9.2342.19200300.100.1.25               |
   |       | DER:             06 0A 09 92 26 89 93 F2 2C 64 01 19      |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    24 | Name:            Postal Address                           |
   |       | Identifiers:     postalAddress                            |
   |       | OID:             2.5.4.16                                 |
   |       | DER:             06 03 55 04 10                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    25 | Name:            Name                                     |
   |       | Identifiers:     name                                     |
   |       | OID:             2.5.4.41                                 |
   |       | DER:             06 03 55 04 29                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    26 | Name:            Telephone Number                         |
   |       | Identifiers:     telephoneNumber                          |
   |       | OID:             2.5.4.20                                 |
   |       | DER:             06 03 55 04 14                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    27 | Name:            Directory Management Domain Name         |
   |       | Identifiers:     dmdName                                  |
   |       | OID:             2.5.4.54                                 |
   |       | DER:             06 03 55 04 36                           |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    28 | Name:            userid                                   |
   |       | Identifiers:     uid                                      |
   |       | OID:             0.9.2342.19200300.100.1.1                |
   |       | DER:             06 0A 09 92 26 89 93 F2 2C 64 01 01      |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    29 | Name:            Unstructured Name                        |
   |       | Identifiers:     unstructuredName                         |
   |       | OID:             1.2.840.113549.1.9.2                     |



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   |       | DER:             06 09 2A 86 48 86 F7 0D 01 09 02         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    30 | Name:            Unstructured Address                     |
   |       | Identifiers:     unstructuredAddress                      |
   |       | OID:             1.2.840.113549.1.9.8                     |
   |       | DER:             06 0A 2A 86 48 86 F7 0D 01 09 08 00      |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    31 | Name:            Mac Address                              |
   |       | Identifiers:     macAddress                               |
   |       | OID:             1.3.6.1.1.1.1.22                         |
   |       | DER:             06 07 2B 06 01 01 01 01 16               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+

                         Figure 10: C509 Attributes

9.5.  C509 Extensions Registry

   IANA has created a new registry titled "C509 Extensions Registry"
   under the new heading "CBOR Encoded X.509 (C509) Parameters".  The
   columns of the registry are Value, Name, Identifiers, OID, DER,
   Comments, extensionValue, and Reference, where Value is a positive
   integer, and the other columns are text strings.  The columns Name,
   OID, DER, abd extensionValue are mandatory.  The registry also
   contains certificate request attributes for use in Certificate
   Requests, see Section 4.  For values in the interval [1, 23] the
   registration procedure is "IETF Review" and "Expert Review".  Values
   ≥ 32768 are reserved for Private Use. For all other values the
   registration procedure is "Expert Review".  The initial contents of
   the registry are:

   +-------+-----------------------------------------------------------+
   | Value | Extension                                                 |
   +=======+===========================================================+
   |     1 | Name:            Subject Key Identifier                   |
   |       | Identifiers:     subjectKeyIdentifier                     |
   |       | OID:             2.5.29.14                                |
   |       | DER:             06 03 55 1D 0E                           |
   |       | Comments:                                                 |
   |       | extensionValue:  SubjectKeyIdentifier                     |
   +-------+-----------------------------------------------------------+
   |     2 | Name:            Key Usage                                |
   |       | Identifiers:     keyUsage                                 |
   |       | OID:             2.5.29.15                                |
   |       | DER:             06 03 55 1D 0F                           |
   |       | Comments:                                                 |



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   |       | AttributeValue:  KeyUsage                                 |
   +-------+-----------------------------------------------------------+
   |     3 | Name:            Subject Alternative Name                 |
   |       | Identifiers:     subjectAltName                           |
   |       | OID:             2.5.29.17                                |
   |       | DER:             06 03 55 1D 11                           |
   |       | Comments:                                                 |
   |       | extensionValue:  SubjectAltName                           |
   +-------+-----------------------------------------------------------+
   |     4 | Name:            Basic Constraints                        |
   |       | Identifiers:     basicConstraints                         |
   |       | OID:             2.5.29.19                                |
   |       | DER:             06 03 55 1D 13                           |
   |       | Comments:                                                 |
   |       | extensionValue:  BasicConstraints                         |
   +-------+-----------------------------------------------------------+
   |     5 | Name:            CRL Distribution Points                  |
   |       | Identifiers:     cRLDistributionPoints                    |
   |       | OID:             2.5.29.31                                |
   |       | DER:             06 03 55 1D 1F                           |
   |       | Comments:                                                 |
   |       | extensionValue:  CRLDistributionPoints                    |
   +-------+-----------------------------------------------------------+
   |     6 | Name:            Certificate Policies                     |
   |       | Identifiers:     certificatePolicies                      |
   |       | OID:             2.5.29.32                                |
   |       | DER:             06 03 55 1D 20                           |
   |       | Comments:                                                 |
   |       | extensionValue:  CertificatePolicies                      |
   +-------+-----------------------------------------------------------+
   |     7 | Name:            Authority Key Identifier                 |
   |       | Identifiers:     authorityKeyIdentifier                   |
   |       | OID:             2.5.29.35                                |
   |       | DER:             06 03 55 1D 23                           |
   |       | Comments:                                                 |
   |       | extensionValue:  AuthorityKeyIdentifier                   |
   +-------+-----------------------------------------------------------+
   |     8 | Name:            Extended Key Usage                       |
   |       | Identifiers:     extKeyUsage                              |
   |       | OID:             2.5.29.37                                |
   |       | DER:             06 03 55 1D 25                           |
   |       | Comments:                                                 |
   |       | extensionValue:  ExtKeyUsageSyntax                        |
   +-------+-----------------------------------------------------------+
   |     9 | Name:            Authority Information Access             |
   |       | Identifiers:     authorityInfoAccess                      |
   |       | OID:             1.3.6.1.5.5.7.1.1                        |
   |       | DER:             06 08 2B 06 01 05 05 07 01 01            |



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   |       | Comments:                                                 |
   |       | extensionValue:  AuthorityInfoAccessSyntax                |
   +-------+-----------------------------------------------------------+
   |    10 | Name:            Signed Certificate Timestamp List        |
   |       | Identifiers:                                              |
   |       | OID:             1.3.6.1.4.1.11129.2.4.2                  |
   |       | DER:             06 0A 2B 06 01 04 01 D6 79 02 04 02      |
   |       | Comments:                                                 |
   |       | extensionValue:  SignedCertificateTimestamps              |
   +-------+-----------------------------------------------------------+
   |    24 | Name:            Subject Directory Attributes             |
   |       | Identifiers:     subjectDirectoryAttributes               |
   |       | OID:             2.5.29.9                                 |
   |       | DER:             06 03 55 1D 09                           |
   |       | Comments:                                                 |
   |       | extensionValue:  SubjectDirectoryAttributes               |
   +-------+-----------------------------------------------------------+
   |    25 | Name:            Issuer Alternative Name                  |
   |       | Identifiers:     issuerAltName                            |
   |       | OID:             2.5.29.18                                |
   |       | DER:             06 03 55 1D 12                           |
   |       | Comments:                                                 |
   |       | extensionValue:  IssuerAltName                            |
   +-------+-----------------------------------------------------------+
   |    26 | Name:            Name Constraints                         |
   |       | Identifiers:     nameConstraints                          |
   |       | OID:             2.5.29.30                                |
   |       | DER:             06 03 55 1D 1E                           |
   |       | Comments:                                                 |
   |       | extensionValue:  NameConstraints                          |
   +-------+-----------------------------------------------------------+
   |    27 | Name:            Policy Mappings                          |
   |       | Identifiers:     policyMappings                           |
   |       | OID:             2.5.29.33                                |
   |       | DER:             06 03 55 1D 21                           |
   |       | Comments:                                                 |
   |       | extensionValue:  PolicyMappings                           |
   +-------+-----------------------------------------------------------+
   |    28 | Name:            Policy Constraints                       |
   |       | Identifiers:     policyConstraints                        |
   |       | OID:             2.5.29.36                                |
   |       | DER:             06 03 55 1D 24                           |
   |       | Comments:                                                 |
   |       | extensionValue:  PolicyConstraints                        |
   +-------+-----------------------------------------------------------+
   |    29 | Name:            Freshest CRL                             |
   |       | Identifiers:     freshestCRL                              |
   |       | OID:             2.5.29.46                                |



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   |       | DER:             06 03 55 1D 2E                           |
   |       | Comments:                                                 |
   |       | extensionValue:  FreshestCRL                              |
   +-------+-----------------------------------------------------------+
   |    30 | Name:            Inhibit anyPolicy                        |
   |       | Identifiers:     inhibitAnyPolicy                         |
   |       | OID:             2.5.29.54                                |
   |       | DER:             06 03 55 1D 36                           |
   |       | Comments:                                                 |
   |       | extensionValue:  InhibitAnyPolicy                         |
   +-------+-----------------------------------------------------------+
   |    31 | Name:            Subject Information Access               |
   |       | Identifiers:     subjectInfoAccess                        |
   |       | OID:             1.3.6.1.5.5.7.1.11                       |
   |       | DER:             06 08 2B 06 01 05 05 07 01 0B            |
   |       | Comments:                                                 |
   |       | extensionValue:  SubjectInfoAccessSyntax                  |
   +-------+-----------------------------------------------------------+
   |    32 | Name:            IP Resources                             |
   |       | Identifiers:     id-pe-ipAddrBlocks                       |
   |       | OID:             1.3.6.1.5.5.7.1.7                        |
   |       | DER:             06 08 2B 06 01 05 05 07 01 07            |
   |       | Comments:                                                 |
   |       | extensionValue:  IPAddrBlocks                             |
   +-------+-----------------------------------------------------------+
   |    33 | Name:            AS Resources                             |
   |       | Identifiers:     id-pe-autonomousSysIds                   |
   |       | OID:             1.3.6.1.5.5.7.1.8                        |
   |       | DER:             06 08 2B 06 01 05 05 07 01 08            |
   |       | Comments:                                                 |
   |       | extensionValue:  ASIdentifiers                            |
   +-------+-----------------------------------------------------------+
   |    34 | Name:            IP Resources v2                          |
   |       | Identifiers:     id-pe-ipAddrBlocks-v2                    |
   |       | OID:             1.3.6.1.5.5.7.1.28                       |
   |       | DER:             06 08 2B 06 01 05 05 07 01 1C            |
   |       | Comments:                                                 |
   |       | extensionValue:  IPAddrBlocks                             |
   +-------+-----------------------------------------------------------+
   |    35 | Name:            AS Resources v2                          |
   |       | Identifiers:     id-pe-autonomousSysIds-v2                |
   |       | OID:             1.3.6.1.5.5.7.1.29                       |
   |       | DER:             06 08 2B 06 01 05 05 07 01 1D            |
   |       | Comments:                                                 |
   |       | extensionValue:  ASIdentifiers                            |
   +-------+-----------------------------------------------------------+
   |    36 | Name:            OCSP No Check                            |
   |       | Identifiers:     id-pkix-ocsp-nocheck                     |



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   |       | OID:             1.3.6.1.5.5.7.48.1.5                     |
   |       | DER:             06 09 2B 06 01 05 05 07 30 01 05         |
   |       | Comments:                                                 |
   |       | extensionValue:  h''                                      |
   +-------+-----------------------------------------------------------+
   |    37 | Name:            Precertificate Signing Certificate       |
   |       | Identifiers:                                              |
   |       | OID:             1.3.6.1.4.1.11129.2.4.3                  |
   |       | DER:             06 0A 2B 06 01 04 01 D6 79 02 04 03      |
   |       | Comments:        RFC 6962                                 |
   |       | extensionValue:  h''                                      |
   +-------+-----------------------------------------------------------+
   |    38 | Name:            TLS Features                             |
   |       | Identifiers:     id-pe-tlsfeature                         |
   |       | OID:             1.3.6.1.5.5.7.1.24                       |
   |       | DER:             06 08 2B 06 01 05 05 07 01 18            |
   |       | Comments:        RFC 7633                                 |
   |       | extensionValue:  TLSFeatures                              |
   +-------+-----------------------------------------------------------+
   |   255 | Name:            Challenge Password                       |
   |       | Identifiers:     challengePassword                        |
   |       | OID:             1.2.840.113549.1.9.7                     |
   |       | DER:             06 09 2A 86 48 86 F7 0D 01 09 07         |
   |       | Comments:        Certificate Request Attributes           |
   |       | extensionValue:  ChallengePassword                        |
   +-------+-----------------------------------------------------------+

       Figure 11: C509 Extensions and Certificate Request Attributes

9.6.  C509 Certificate Policies Registry

   IANA has created a new registry titled "C509 Certificate Policies
   Registry" under the new heading "CBOR Encoded X.509 (C509)
   Parameters".  The columns of the registry are Value, Name,
   Identifiers, OID, DER, Comments, and Reference, where Value is an
   integer, and the other columns are text strings.  The columns Name,
   OID, and DER are mandatory.  For values in the interval [-24, 23] the
   registration procedure is "IETF Review" and "Expert Review".  Values
   ≥ 32768 are reserved for Private Use. For all other values the
   registration procedure is "Expert Review".  The initial contents of
   the registry are:

   +-------+-----------------------------------------------------------+
   | Value | Certificate Policy                                        |
   +=======+===========================================================+
   |     0 | Name:            Any Policy                               |
   |       | Identifiers:     anyPolicy                                |
   |       | OID:             2.5.29.32.0                              |



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   |       | DER:             06 04 55 1D 20 00                        |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     1 | Name:            Domain Validation (DV)                   |
   |       | Identifiers:     domain-validated                         |
   |       | OID:             2.23.140.1.2.1                           |
   |       | DER:             06 06 67 81 0C 01 02 01                  |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     2 | Name:            Organization Validation (OV)             |
   |       | Identifiers:     organization-validated                   |
   |       | OID:             2.23.140.1.2.2                           |
   |       | DER:             06 06 67 81 0C 01 02 02                  |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     3 | Name:            Individual Validation (IV)               |
   |       | Identifiers:     individual-validated                     |
   |       | OID:             2.23.140.1.2.3                           |
   |       | DER:             06 06 67 81 0C 01 02 03                  |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     4 | Name:            Extended Validation (EV)                 |
   |       | Identifiers:     ev-guidelines                            |
   |       | OID:             2.23.140.1.1                             |
   |       | DER:             06 05 67 81 0C 01 01                     |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     7 | Name:            Resource PKI (RPKI)                      |
   |       | Identifiers:     id-cp-ipAddr-asNumber                    |
   |       | OID:             1.3.6.1.5.5.7.14.2                       |
   |       | DER:             06 08 2B 06 01 05 05 07 0E 02            |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     8 | Name:            Resource PKI (RPKI) (Alternative)        |
   |       | Identifiers:     id-cp-ipAddr-asNumber-v2                 |
   |       | OID:             1.3.6.1.5.5.7.14.3                       |
   |       | DER:             06 08 2B 06 01 05 05 07 0E 03            |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    10 | Name:            Remote SIM Provisioning Role             |
   |       |                  Certificate Issuer                       |
   |       | Identifiers:     id-rspRole-ci                            |
   |       | OID:             2.23.146.1.2.1.0                         |
   |       | DER:             06 07 67 81 12 01 02 01 00               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    11 | Name:            Remote SIM Provisioning Role             |
   |       |                  eUICC                                    |



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   |       | Identifiers:     id-rspRole-euicc                         |
   |       | OID:             2.23.146.1.2.1.1                         |
   |       | DER:             06 07 67 81 12 01 02 01 01               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    12 | Name:            Remote SIM Provisioning Role             |
   |       |                  eUICC Manufacturer                       |
   |       | Identifiers:     id-rspRole-eum                           |
   |       | OID:             2.23.146.1.2.1.2                         |
   |       | DER:             06 07 67 81 12 01 02 01 02               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    13 | Name:            Remote SIM Provisioning Role             |
   |       |                  SM-DP+ TLS                               |
   |       | Identifiers:     id-rspRole-dp-tls                        |
   |       | OID:             2.23.146.1.2.1.3                         |
   |       | DER:             06 07 67 81 12 01 02 01 03               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    14 | Name:            Remote SIM Provisioning Role             |
   |       |                  SM-DP+ Authentication                    |
   |       | Identifiers:     id-rspRole-dp-auth                       |
   |       | OID:             2.23.146.1.2.1.4                         |
   |       | DER:             06 07 67 81 12 01 02 01 04               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    15 | Name:            Remote SIM Provisioning Role             |
   |       |                  SM-DP+ Profile Binding                   |
   |       | Identifiers:     id-rspRole-dp-pb                         |
   |       | OID:             2.23.146.1.2.1.5                         |
   |       | DER:             06 07 67 81 12 01 02 01 05               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    16 | Name:            Remote SIM Provisioning Role             |
   |       |                  SM-DS TLS                                |
   |       | Identifiers:     id-rspRole-ds-tls                        |
   |       | OID:             2.23.146.1.2.1.6                         |
   |       | DER:             06 07 67 81 12 01 02 01 06               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    17 | Name:            Remote SIM Provisioning Role             |
   |       |                  SM-DS Authentication                     |
   |       | Identifiers:     id-rspRole-ds-auth                       |
   |       | OID:             2.23.146.1.2.1.7                         |
   |       | DER:             06 07 67 81 12 01 02 01 07               |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+




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                    Figure 12: C509 Certificate Policies

9.7.  C509 Policies Qualifiers Registry

   IANA has created a new registry titled "C509 Policies Qualifiers
   Registry" under the new heading "CBOR Encoded X.509 (C509)
   Parameters".  The columns of the registry are Value, Name,
   Identifiers, OID, DER, Comments, and Reference, where Value is an
   integer, and the other columns are text strings.  The columns Name,
   OID, and DER are mandatory.  For values in the interval [-24, 23] the
   registration procedure is "IETF Review" and "Expert Review".  Values
   ≥ 32768 are reserved for Private Use. For all other values the
   registration procedure is "Expert Review".  The initial contents of
   the registry are:

   +-------+-----------------------------------------------------------+
   | Value | Certificate Policy                                        |
   +=======+===========================================================+
   |     1 | Name:            Certification Practice Statement         |
   |       | Identifiers:     id-qt-cps, cps                           |
   |       | OID:             1.3.6.1.5.5.7.2.1                        |
   |       | DER:             06 08 2B 06 01 05 05 07 02 01            |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     2 | Name:            User Notice                              |
   |       | Identifiers:     id-qt-unotice, unotice                   |
   |       | OID:             1.3.6.1.5.5.7.2.2                        |
   |       | DER:             06 08 2B 06 01 05 05 07 02 02            |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+

                    Figure 13: C509 Policies Qualifiers

9.8.  C509 Information Access Registry

   IANA has created a new registry titled "C509 Information Access
   Registry" under the new heading "CBOR Encoded X.509 (C509)
   Parameters".  The columns of the registry are Value, Name,
   Identifiers, OID, DER, Comments, and Reference, where Value is an
   integer, and the other columns are text strings.  The columns Name,
   OID, and DER are mandatory.  For values in the interval [-24, 23] the
   registration procedure is "IETF Review" and "Expert Review".  For all
   other values the registration procedure is "Expert Review".  The
   initial contents of the registry are:







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   +-------+-----------------------------------------------------------+
   | Value | Information Access                                        |
   +=======+===========================================================+
   |     1 | Name:            OCSP                                     |
   |       | Identifiers:     id-ad-ocsp, id-pkix-ocsp                 |
   |       | OID:             1.3.6.1.5.5.7.48.1                       |
   |       | DER:             06 08 2B 06 01 05 05 07 30 01            |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     2 | Name:            CA Issuers                               |
   |       | Identifiers:     id-ad-caIssuers, caIssuers               |
   |       | OID:             1.3.6.1.5.5.7.48.2                       |
   |       | DER:             06 08 2B 06 01 05 05 07 30 02            |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     3 | Name:            Time Stamping                            |
   |       | Identifiers:     id-ad-timeStamping, timeStamping         |
   |       | OID:             1.3.6.1.5.5.7.48.3                       |
   |       | DER:             06 08 2B 06 01 05 05 07 30 03            |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     5 | Name:            CA Repository                            |
   |       | Identifiers:     id-ad-caRepository                       |
   |       | OID:             1.3.6.1.5.5.7.48.5                       |
   |       | DER:             06 08 2B 06 01 05 05 07 30 05            |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    10 | Name:            RPKI Manifest                            |
   |       | Identifiers:     id-ad-rpkiManifest                       |
   |       | OID:             1.3.6.1.5.5.7.48.10                      |
   |       | DER:             06 08 2B 06 01 05 05 07 30 0A            |
   |       | Comments:        RFC 6487                                 |
   +-------+-----------------------------------------------------------+
   |    11 | Name:            Signed Object                            |
   |       | Identifiers:     id-ad-signedObject                       |
   |       | OID:             1.3.6.1.5.5.7.48.11                      |
   |       | DER:             06 08 2B 06 01 05 05 07 30 0B            |
   |       | Comments:        RFC 6487                                 |
   +-------+-----------------------------------------------------------+
   |    13 | Name:            RPKI Notify                              |
   |       | Identifiers:     id-ad-rpkiNotify                         |
   |       | OID:             1.3.6.1.5.5.7.48.13                      |
   |       | DER:             06 08 2B 06 01 05 05 07 30 0D            |
   |       | Comments:        RFC 8182                                 |
   +-------+-----------------------------------------------------------+

                    Figure 14: C509 Information Accesses




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9.9.  C509 Extended Key Usages Registry

   IANA has created a new registry titled "C509 Extended Key Usages
   Registry" under the new heading "CBOR Encoded X.509 (C509)
   Parameters".  The columns of the registry are Value, Name,
   Identifiers, OID, DER, Comments, and Reference, where Value is an
   integer, and the other columns are text strings.  The columns Name,
   OID, and DER are mandatory.  For values in the interval [-24, 23] the
   registration procedure is "IETF Review" and "Expert Review".  Values
   ≥ 32768 are reserved for Private Use. For all other values the
   registration procedure is "Expert Review".  The initial contents of
   the registry are:

    +-------+---------------------------------------------------------+
    | Value | Extended Key Usage                                      |
    +=======+=========================================================+
    |     0 | Name:            Any Extended Key Usage                 |
    |       | Identifiers:     anyExtendedKeyUsage                    |
    |       | OID:             2.5.29.37.0                            |
    |       | DER:             06 04 55 1D 25 00                      |
    |       | Comments:        RFC 5280                               |
    +-------+---------------------------------------------------------+
    |     1 | Name:            TLS Server authentication              |
    |       | Identifiers:     id-kp-serverAuth                       |
    |       | OID:             1.3.6.1.5.5.7.3.1                      |
    |       | DER:             06 08 2B 06 01 05 05 07 03 01          |
    |       | Comments:        RFC 5280                               |
    +-------+---------------------------------------------------------+
    |     2 | Name:            TLS Client Authentication              |
    |       | Identifiers:     id-kp-clientAuth                       |
    |       | OID:             1.3.6.1.5.5.7.3.2                      |
    |       | DER:             06 08 2B 06 01 05 05 07 03 02          |
    |       | Comments:        RFC 5280                               |
    +-------+---------------------------------------------------------+
    |     3 | Name:            Code Signing                           |
    |       | Identifiers:     id-kp-codeSigning                      |
    |       | OID:             1.3.6.1.5.5.7.3.3                      |
    |       | DER:             06 08 2B 06 01 05 05 07 03 03          |
    |       | Comments:        RFC 5280                               |
    +-------+---------------------------------------------------------+
    |     4 | Name:            Email protection (S/MIME)              |
    |       | Identifiers:     id-kp-emailProtection                  |
    |       | OID:             1.3.6.1.5.5.7.3.4                      |
    |       | DER:             06 08 2B 06 01 05 05 07 03 04          |
    |       | Comments:        RFC 5280                               |
    +-------+---------------------------------------------------------+
    |     8 | Name:            Time Stamping                          |
    |       | Identifiers:     id-kp-timeStamping, timestamping       |



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    |       | OID:             1.3.6.1.5.5.7.3.8                      |
    |       | DER:             06 08 2B 06 01 05 05 07 03 08          |
    |       | Comments:                                               |
    +-------+---------------------------------------------------------+
    |     9 | Name:            OCSP Signing                           |
    |       | Identifiers:     id-kp-OCSPSigning                      |
    |       | OID:             1.3.6.1.5.5.7.3.9                      |
    |       | DER:             06 08 2B 06 01 05 05 07 03 09          |
    |       | Comments:        RFC 5280                               |
    +-------+---------------------------------------------------------+
    |    10 | Name:            Kerberos PKINIT Client Auth            |
    |       | Identifiers:     id-pkinit-KPClientAuth                 |
    |       | OID:             1.3.6.1.5.2.3.4                        |
    |       | DER:             06 07 2B 06 01 05 02 03 04             |
    |       | Comments:        RFC 4556                               |
    +-------+---------------------------------------------------------+
    |    11 | Name:            Kerberos PKINIT KDC                    |
    |       | Identifiers:     id-pkinit-KPKdc                        |
    |       | OID:             1.3.6.1.5.2.3.5                        |
    |       | DER:             06 07 2B 06 01 05 02 03 05             |
    |       | Comments:        RFC 4556                               |
    +-------+---------------------------------------------------------+
    |    12 | Name:            SSH Client                             |
    |       | Identifiers:     id-kp-secureShellClient                |
    |       | OID:             1.3.6.1.5.5.7.3.21                     |
    |       | DER:             06 08 2B 06 01 05 05 07 03 15          |
    |       | Comments:        RFC 6187                               |
    +-------+---------------------------------------------------------+
    |    13 | Name:            SSH Server                             |
    |       | Identifiers:     id-kp-secureShellServer                |
    |       | OID:             1.3.6.1.5.5.7.3.22                     |
    |       | DER:             06 08 2B 06 01 05 05 07 03 16          |
    |       | Comments:        RFC 6187                               |
    +-------+---------------------------------------------------------+
    |    14 | Name:            Bundle Security                        |
    |       | Identifiers:     id-kp-bundleSecurity                   |
    |       | OID:             1.3.6.1.5.5.7.3.35                     |
    |       | DER:             06 08 2B 06 01 05 05 07 03 23          |
    |       | Comments:        RFC 9174                               |
    +-------+---------------------------------------------------------+
    |    15 | Name:            CMC Certification Authority            |
    |       | Identifiers:     id-kp-cmcCA                            |
    |       | OID:             1.3.6.1.5.5.7.3.27                     |
    |       | DER:             06 08 2B 06 01 05 05 07 03 1B          |
    |       | Comments:        RFC 6402                               |
    +-------+---------------------------------------------------------+
    |    16 | Name:            CMC Registration Authority             |
    |       | Identifiers:     id-kp-cmcRA                            |



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    |       | OID:             1.3.6.1.5.5.7.3.28                     |
    |       | DER:             06 08 2B 06 01 05 05 07 03 1C          |
    |       | Comments:        RFC 6402                               |
    +-------+---------------------------------------------------------+
    |    17 | Name:            CMC Archive Server                     |
    |       | Identifiers:     id-kp-cmcArchive                       |
    |       | OID:             1.3.6.1.5.5.7.3.29                     |
    |       | DER:             06 08 2B 06 01 05 05 07 03 1D          |
    |       | Comments:        RFC 6402                               |
    +-------+---------------------------------------------------------+
    |    18 | Name:            CMC Key Generation Authority           |
    |       | Identifiers:     id-kp-cmKGA                            |
    |       | OID:             1.3.6.1.5.5.7.3.32                     |
    |       | DER:             06 08 2B 06 01 05 05 07 03 20          |
    |       | Comments:        RFC 9480                               |
    +-------+---------------------------------------------------------+
    |    19 | Name:            Precertificate Signing Certificate     |
    |       | Identifiers:                                            |
    |       | OID:             1.3.6.1.4.1.11129.2.4.4                |
    |       | DER:             06 0A 2B 06 01 04 01 D6 79 02 04 04    |
    |       | Comments:        RFC 6962                               |
    +-------+---------------------------------------------------------+

                    Figure 15: C509 Extended Key Usages

9.10.  C509 General Names Registry

   IANA has created a new registry titled "C509 General Names Registry"
   under the new heading "CBOR Encoded X.509 (C509) Parameters".  The
   columns of the registry are Value, General Name, and Reference, where
   Value is an integer, and the other columns are text strings.  The
   columns Name and Value are mandatory.  For values in the interval
   [-24, 23] the registration procedure is "IETF Review" and "Expert
   Review".  For all other values the registration procedure is "Expert
   Review".  The initial contents of the registry are:
















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   +-------+-----------------------------------------------------------+
   | Value | General Names                                             |
   +=======+===========================================================+
   |    -2 | Name:            otherName with SmtpUTF8Mailbox           |
   |       | Comments:        id-on-SmtpUTF8Mailbox                    |
   |       |                  (1.3.6.1.5.5.7.8.9)                      |
   |       |                  06 08 2B 06 01 05 05 07 08 09            |
   |       | Value:           text                                     |
   +-------+-----------------------------------------------------------+
   |    -1 | Name:            otherName with hardwareModuleName        |
   |       | Comments:        id-on-hardwareModuleName                 |
   |       |                  (1.3.6.1.5.5.7.8.4)                      |
   |       |                  06 08 2B 06 01 05 05 07 08 04            |
   |       | Value:           [ ~oid, bytes ]                          |
   +-------+-----------------------------------------------------------+
   |     0 | Name:            otherName                                |
   |       | Comments:                                                 |
   |       | Value:           [ ~oid, bytes ]                          |
   +-------+-----------------------------------------------------------+
   |     1 | Name:            rfc822Name                               |
   |       | Comments:                                                 |
   |       | Value:           text                                     |
   +-------+-----------------------------------------------------------+
   |     2 | Name:            dNSName                                  |
   |       | Comments:                                                 |
   |       | Value:           text                                     |
   +-------+-----------------------------------------------------------+
   |     4 | Name:            directoryName                            |
   |       | Comments:                                                 |
   |       | Value:           Name                                     |
   +-------+-----------------------------------------------------------+
   |     6 | Name:            uniformResourceIdentifier                |
   |       | Comments:                                                 |
   |       | Value:           text                                     |
   +-------+-----------------------------------------------------------+
   |     7 | Name:            iPAddress                                |
   |       | Comments:                                                 |
   |       | Value:           bytes                                    |
   +-------+-----------------------------------------------------------+
   |     8 | Name:            registeredID                             |
   |       | Comments:                                                 |
   |       | Value:           ~oid                                     |
   +-------+-----------------------------------------------------------+

                       Figure 16: C509 General Names






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9.11.  C509 Signature Algorithms Registry

   IANA has created a new registry titled "C509 Signature Algorithms"
   under the new heading "CBOR Encoded X.509 (C509) Parameters".  The
   registry includes both signature algorithms and non-signature proof-
   of-possession algorithms.  The columns of the registry are Value,
   Name, Identifiers, OID, Parameters, DER, Comments, and Reference,
   where Value is an integer, and the other columns are text strings.
   The columns Name, OID, Parameters, and DER are mandatory.  For values
   in the interval [-24, 23] the registration procedure is "IETF Review"
   and "Expert Review".  For all other values the registration procedure
   is "Expert Review".  The initial contents of the registry are:

   +-------+-----------------------------------------------------------+
   | Value | X.509 Signature Algorithms                                |
   +=======+===========================================================+
   |  -256 | Name:        RSASSA-PKCS1-v1_5 with SHA-1                 |
   |       | Identifiers: sha1-with-rsa-signature,                     |
   |       |              sha1WithRSAEncryption,                       |
   |       |              sha-1WithRSAEncryption                       |
   |       | OID:         1.2.840.113549.1.1.5                         |
   |       | Parameters:  NULL                                         |
   |       | DER:         30 0D 06 09 2A 86 48 86 F7 0D 01 01 05 05 00 |
   |       | Comments:    Don't use                                    |
   +-------+-----------------------------------------------------------+
   |  -255 | Name:        ECDSA with SHA-1                             |
   |       | Identifiers: ecdsa-with-SHA1                              |
   |       | OID:         1.2.840.10045.4.1                            |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 09 06 07 2A 86 48 CE 3D 04 01             |
   |       | Comments:    Don't use. Compressed signature value        |
   +-------+-----------------------------------------------------------+
   |     0 | Name:        ECDSA with SHA-256                           |
   |       | Identifiers: ecdsa-with-SHA256                            |
   |       | OID:         1.2.840.10045.4.3.2                          |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2A 86 48 CE 3D 04 03 02          |
   |       | Comments:    Compressed signature value                   |
   +-------+-----------------------------------------------------------+
   |     1 | Name:        ECDSA with SHA-384                           |
   |       | Identifiers: ecdsa-with-SHA384                            |
   |       | OID:         1.2.840.10045.4.3.3                          |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2A 86 48 CE 3D 04 03 03          |
   |       | Comments:    Compressed signature value                   |
   +-------+-----------------------------------------------------------+
   |     2 | Name:        ECDSA with SHA-512                           |
   |       | Identifiers: ecdsa-with-SHA512                            |



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   |       | OID:         1.2.840.10045.4.3.4                          |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2A 86 48 CE 3D 04 03 04          |
   |       | Comments:    Compressed signature value                   |
   +-------+-----------------------------------------------------------+
   |     3 | Name:        ECDSA with SHAKE128                          |
   |       | Identifiers: id-ecdsa-with-shake128                       |
   |       | OID:         1.3.6.1.5.5.7.6.32                           |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2B 06 01 05 05 07 06 20          |
   |       | Comments:    Compressed signature value                   |
   +-------+-----------------------------------------------------------+
   |     4 | Name:        ECDSA with SHAKE256                          |
   |       | Identifiers: id-ecdsa-with-shake256                       |
   |       | OID:         1.3.6.1.5.5.7.6.33                           |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2B 06 01 05 05 07 06 21          |
   |       | Comments:    Compressed signature value                   |
   +-------+-----------------------------------------------------------+
   |    12 | Name:        Ed25519                                      |
   |       | Identifiers: id-Ed25519, id-EdDSA25519                    |
   |       | OID:         1.3.101.112                                  |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 05 06 03 2B 65 70                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    13 | Name:        Ed448                                        |
   |       | Identifiers: id-Ed448, id-EdDSA448                        |
   |       | OID:         1.3.101.113                                  |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 05 06 03 2B 65 71                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    14 | Name:        SHA-256 with HMAC-SHA256                     |
   |       | Identifiers: sa-ecdhPop-sha256-hmac-sha256                |
   |       | OID:         1.3.6.1.5.5.7.6.26                           |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2B 06 01 05 05 07 06 1A          |
   |       | Comments:    Proof-of-possession algorithm, indexed with  |
   |       |              KDF and MAC, see RFC 6955. Requires          |
   |       |              recipient public static Diffie-Hellman key.  |
   +-------+-----------------------------------------------------------+
   |    15 | Name:        SHA-384 with HMAC-SHA384                     |
   |       | Identifiers: sa-ecdhPop-sha384-hmac-sha384                |
   |       | OID:         1.3.6.1.5.5.7.6.27                           |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2B 06 01 05 05 07 06 1B          |
   |       | Comments:    Proof-of-possession algorithm, indexed with  |



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   |       |              KDF and MAC, see RFC 6955. Requires          |
   |       |              recipient public static Diffie-Hellman key.  |
   +-------+-----------------------------------------------------------+
   |    16 | Name:        SHA-512 with HMAC-SHA512                     |
   |       | Identifiers: sa-ecdhPop-sha512-hmac-sha512                |
   |       | OID:         1.3.6.1.5.5.7.6.28                           |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2B 06 01 05 05 07 06 1C          |
   |       | Comments:    Proof-of-possession algorithm, indexed with  |
   |       |              KDF and MAC, see RFC 6955. Requires          |
   |       |              recipient public static Diffie-Hellman key.  |
   +-------+-----------------------------------------------------------+
   |    23 | Name:        RSASSA-PKCS1-v1_5 with SHA-256               |
   |       | Identifiers: sha256WithRSAEncryption                      |
   |       | OID:         1.2.840.113549.1.1.11                        |
   |       | Parameters:  NULL                                         |
   |       | DER:         30 0B 06 09 2A 86 48 86 F7 0D 01 01 0B 05 00 |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    24 | Name:        RSASSA-PKCS1-v1_5 with SHA-384               |
   |       | Identifiers: sha384WithRSAEncryption                      |
   |       | OID:         1.2.840.113549.1.1.12                        |
   |       | Parameters:  NULL                                         |
   |       | DER:         30 0B 06 09 2A 86 48 86 F7 0D 01 01 0C 05 00 |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    25 | Name:        RSASSA-PKCS1-v1_5 with SHA-512               |
   |       | Identifiers: sha512WithRSAEncryption                      |
   |       | OID:         1.2.840.113549.1.1.13                        |
   |       | Parameters:  NULL                                         |
   |       | DER:         30 0B 06 09 2A 86 48 86 F7 0D 01 01 0D 05 00 |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    26 | Name:        RSASSA-PSS with SHA-256                      |
   |       | Identifiers: rsassa-pss, id-RSASSA-PSS                    |
   |       | OID:         1.2.840.113549.1.1.10                        |
   |       | Parameters:  SHA-256, MGF-1 with SHA-256, saltLength = 32 |
   |       | DER:         30 41 06 09 2A 86 48 86 F7 0D 01 01 0A 30 34 |
   |       |              A0 0F 30 0D 06 09 60 86 48 01 65 03 04 02 01 |
   |       |              05 00 A1 1C 30 1A 06 09 2A 86 48 86 F7 0D 01 |
   |       |              01 08 30 0D 06 09 60 86 48 01 65 03 04 02 01 |
   |       |              05 00 a2 03 02 01 20                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    27 | Name:        RSASSA-PSS with SHA-384                      |
   |       | Identifiers: rsassa-pss, id-RSASSA-PSS                    |
   |       | OID:         1.2.840.113549.1.1.10                        |
   |       | Parameters:  SHA-384, MGF-1 with SHA-384, saltLength = 48 |



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   |       | DER:         30 41 06 09 2A 86 48 86 F7 0D 01 01 0A 30 34 |
   |       |              A0 0F 30 0D 06 09 60 86 48 01 65 03 04 02 02 |
   |       |              05 00 A1 1C 30 1A 06 09 2A 86 48 86 F7 0D 01 |
   |       |              01 08 30 0D 06 09 60 86 48 01 65 03 04 02 02 |
   |       |              05 00 A2 03 02 01 30                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    28 | Name:        RSASSA-PSS with SHA-512                      |
   |       | Identifiers: rsassa-pss, id-RSASSA-PSS                    |
   |       | OID:         1.2.840.113549.1.1.10                        |
   |       | Parameters:  SHA-512, MGF-1 with SHA-512, saltLength = 64 |
   |       | DER:         30 41 06 09 2A 86 48 86 F7 0D 01 01 0A 30 34 |
   |       |              A0 0F 30 0D 06 09 60 86 48 01 65 03 04 02 03 |
   |       |              05 00 A1 1C 30 1A 06 09 2A 86 48 86 F7 0D 01 |
   |       |              01 08 30 0D 06 09 60 86 48 01 65 03 04 02 03 |
   |       |              05 00 A2 03 02 01 40                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    29 | Name:        RSASSA-PSS with SHAKE128                     |
   |       | Identifiers: id-RSASSA-PSS-SHAKE128                       |
   |       | OID:         1.3.6.1.5.5.7.6.30                           |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2B 06 01 05 05 07 06 1E          |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    30 | Name:        RSASSA-PSS with SHAKE256                     |
   |       | Identifiers: id-RSASSA-PSS-SHAKE256                       |
   |       | OID:         1.3.6.1.5.5.7.6.31                           |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2B 06 01 05 05 07 06 1F          |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    45 | Name:        SM2 with SM3                                 |
   |       | Identifiers: sm2-with-sm3                                 |
   |       | OID:         1.2.156.10197.1.501                          |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0A 06 08 2A 81 1C CF 55 01 83 75          |
   |       | Comments:    Compressed signature value                   |
   +-------+-----------------------------------------------------------+

                    Figure 17: C509 Signature Algorithms










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9.12.  C509 Public Key Algorithms Registry

   IANA has created a new registry titled "C509 Public Key Algorithms"
   under the new heading "CBOR Encoded X.509 (C509) Parameters".  The
   columns of the registry are Value, Name, Identifiers, OID,
   Parameters, DER, Comments, and Reference, where Value is an integer,
   and the other columns are text strings.  The columns Name, OID,
   Parameters, and DER are mandatory.  For values in the interval [-24,
   23] the registration procedure is "IETF Review" and "Expert Review".
   For all other values the registration procedure is "Expert Review".
   The initial contents of the registry are:

   +-------+-----------------------------------------------------------+
   | Value | X.509 Public Key Algorithms                               |
   +=======+===========================================================+
   |     0 | Name:        RSA                                          |
   |       | Identifiers: rsaEncryption                                |
   |       | OID:         1.2.840.113549.1.1.1                         |
   |       | Parameters:  NULL                                         |
   |       | DER:         30 0d 06 09 2a 86 48 86 f7 0d 01 01 01 05 00 |
   |       | Comments:    Compressed subjectPublicKey                  |
   +-------+-----------------------------------------------------------+
   |     1 | Name:        EC Public Key (Weierstraß) with secp256r1    |
   |       | Identifiers: ecPublicKey, id-ecPublicKey                  |
   |       | OID:         1.2.840.10045.2.1                            |
   |       | Parameters:  namedCurve = secp256r1 (1.2.840.10045.3.1.7) |
   |       | DER:         30 13 06 07 2A 86 48 CE 3D 02 01 06 08 2A 86 |
   |       |              48 CE 3D 03 01 07                            |
   |       | Comments:    Point compressed subjectPublicKey            |
   |       |              Also known as P-256, ansip256r1, prime256v1  |
   +-------+-----------------------------------------------------------+
   |     2 | Name:        EC Public Key (Weierstraß) with secp384r1    |
   |       | Identifiers: ecPublicKey, id-ecPublicKey                  |
   |       | OID:         1.2.840.10045.2.1                            |
   |       | Parameters:  namedCurve = secp384r1 (1.3.132.0.34)        |
   |       | DER:         30 10 06 07 2A 86 48 CE 3D 02 01 06 05 2B 81 |
   |       |              04 00 22                                     |
   |       | Comments:    Point compressed subjectPublicKey            |
   |       |              Also known as P-384, ansip384r1              |
   +-------+-----------------------------------------------------------+
   |     3 | Name:        EC Public Key (Weierstraß) with secp521r1    |
   |       | Identifiers: ecPublicKey, id-ecPublicKey                  |
   |       | OID:         1.2.840.10045.2.1                            |
   |       | Parameters:  namedCurve = secp521r1 (1.3.132.0.35)        |
   |       | DER:         30 10 06 07 2A 86 48 CE 3D 02 01 06 05 2B 81 |
   |       |              04 00 23                                     |
   |       | Comments:    Point compressed subjectPublicKey            |
   |       |              Also known as P-521, ansip521r1              |



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   +-------+-----------------------------------------------------------+
   |     8 | Name:        X25519 (Montgomery)                          |
   |       | Identifiers: id-X25519                                    |
   |       | OID:         1.3.101.110                                  |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 05 06 03 2B 65 6E                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |     9 | Name:        X448 (Montgomery)                            |
   |       | Identifiers: id-X448                                      |
   |       | OID:         1.3.101.111                                  |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 05 06 03 2B 65 6F                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    10 | Name:        Ed25519 (Twisted Edwards)                    |
   |       | Identifiers: id-Ed25519, id-EdDSA25519                    |
   |       | OID:         1.3.101.112                                  |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 05 06 03 2B 65 70                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    11 | Name:        Ed448 (Edwards)                              |
   |       | Identifiers: id-Ed448, id-EdDSA448                        |
   |       | OID:         1.3.101.113                                  |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 05 06 03 2B 65 71                         |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    16 | Name:        HSS / LMS                                    |
   |       | Identifiers: id-alg-hss-lms-hashsig, id-alg-mts-hashsig   |
   |       | OID:         1.2.840.113549.1.9.16.3.17                   |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0D 06 0B 2A 86 48 86 F7 0D 01 09 10 03 11 |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    17 | Name:        XMSS                                         |
   |       | Identifiers: id_alg_xmss                                  |
   |       | OID:         0.4.0.127.0.15.1.1.13.0                      |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0B 06 09 04 00 7F 00 0F 01 01 0D 00       |
   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    18 | Name:        XMSS^MT                                      |
   |       | Identifiers: id_alg_xmssmt                                |
   |       | OID:         0.4.0.127.0.15.1.1.14.0                      |
   |       | Parameters:  Absent                                       |
   |       | DER:         30 0B 06 09 04 00 7F 00 0F 01 01 0E 00       |



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   |       | Comments:                                                 |
   +-------+-----------------------------------------------------------+
   |    24 | Name:        EC Public Key (Weierstraß) with              |
   |       |              brainpoolP256r1                              |
   |       | Identifiers: ecPublicKey, id-ecPublicKey                  |
   |       | OID:         1.2.840.10045.2.1                            |
   |       | Parameters:  namedCurve = brainpoolP256r1                 |
   |       |              (1.3.36.3.3.2.8.1.1.7)                       |
   |       | DER:         30 14 06 07 2A 86 48 CE 3D 02 01 06 09 2B 24 |
   |       |              03 03 02 08 01 01 07                         |
   |       | Comments:    Point compressed subjectPublicKey            |
   +-------+-----------------------------------------------------------+
   |    25 | Name:        EC Public Key (Weierstraß) with              |
   |       |              brainpoolP384r1                              |
   |       | Identifiers: ecPublicKey, id-ecPublicKey                  |
   |       | OID:         1.2.840.10045.2.1                            |
   |       | Parameters:  namedCurve = brainpoolP384r1                 |
   |       |              (1.3.36.3.3.2.8.1.1.11)                      |
   |       | DER:         30 14 06 07 2A 86 48 CE 3D 02 01 06 09 2B 24 |
   |       |              03 03 02 08 01 01 0B                         |
   |       | Comments:    Point compressed subjectPublicKey            |
   +-------+-----------------------------------------------------------+
   |    26 | Name:        EC Public Key (Weierstraß) with              |
   |       |              brainpoolP512r1                              |
   |       | Identifiers: ecPublicKey, id-ecPublicKey                  |
   |       | OID:         1.2.840.10045.2.1                            |
   |       | Parameters:  namedCurve = brainpoolP512r1                 |
   |       |              (1.3.36.3.3.2.8.1.1.13)                      |
   |       | DER:         30 14 06 07 2A 86 48 CE 3D 02 01 06 09 2B 24 |
   |       |              03 03 02 08 01 01 0D                         |
   |       | Comments:    Point compressed subjectPublicKey            |
   +-------+-----------------------------------------------------------+
   |    27 | Name:        EC Public Key (Weierstraß) with              |
   |       |              FRP256v1                                     |
   |       | Identifiers: ecPublicKey, id-ecPublicKey                  |
   |       | OID:         1.2.840.10045.2.1                            |
   |       | Parameters:  namedCurve = FRP256v1                        |
   |       |              (1.2.250.1.223.101.256.1)                    |
   |       | DER:         30 15 06 07 2A 86 48 CE 3D 02 01 06 0A 2A 81 |
   |       |              7A 01 81 5F 65 82 00 01                      |
   |       | Comments:    Point compressed subjectPublicKey            |
   +-------+-----------------------------------------------------------+
   |    28 | Name:        EC Public Key (Weierstraß) with              |
   |       |              sm2p256v1                                    |
   |       | Identifiers: ecPublicKey, id-ecPublicKey                  |
   |       | OID:         1.2.840.10045.2.1                            |
   |       | Parameters:  namedCurve = sm2p256v1                       |
   |       |              (1.2.156.10197.1.301)                        |



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   |       | DER:         30 13 06 07 2A 86 48 CE 3D 02 01 06 08 2A 81 |
   |       |              1C CF 55 01 82 2D                            |
   |       | Comments:    Point compressed subjectPublicKey            |
   +-------+-----------------------------------------------------------+

                   Figure 18: C509 Public Key Algorithms

9.12.1.  Suitability of different public key algorithms for use within
         IoT scenarios

   The public key algorithms registry Section 9.12 specify a number of
   algorithms, not all which are suitable for usage with constrained
   devices.  RSA requires large keys and large signature sizes compared
   to elliptic curve cryptography (ECC), which together with resource-
   efficient implementations of named elliptic curves (Montgomery,
   Edwards and Weierstraß curves), make them suitable candidates for IoT
   public key usage.  These curves are represented by ids 1–11 and 24–28
   in Section 9.12.

9.13.  COSE Header Parameters Registry

   IANA is requested to assign the entries in Table 1 to the "COSE
   Header Parameters" registry under the "CBOR Object Signing and
   Encryption (COSE)" heading with this document as reference.

9.14.  Media Type application/cose-c509-cert

   When the application/cose-c509-cert media type is used, the data is a
   COSE_C509 structure.  If the parameter "usage" is set to "chain",
   this sequence indicates a certificate chain.

   IANA has registered the following media type [RFC6838]:

   Type name: application

   Subtype name: cose-c509-cert

   Required parameters: N/A

   Optional parameters: usage

   *  Can be absent to provide no further information about the intended
      meaning of the order in the CBOR sequence of certificates.

   *  Can be set to "chain" to indicate that the sequence of data items
      is to be interpreted as a certificate chain.

   Encoding considerations: binary



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   Security considerations: See the Security Considerations section of
   [[this document]].

   Interoperability considerations: N/A

   Published specification: [[this document]]

   Applications that use this media type: Applications that employ COSE
   and use C509 as a certificate type.

   Fragment identifier considerations: N/A

   Additional information:

   *  Deprecated alias names for this type: N/A

   *  Magic number(s): TBD8

   *  File extension(s): .c509

   *  Macintosh file type code(s): N/A

   Person & email address to contact for further information:
   iesg@ietf.org

   Intended usage: COMMON

   Restrictions on usage: N/A

   Author: COSE WG

   Change controller: IESG

9.15.  Media Type application/cose-c509-pkcs10

   When the application/cose-c509-pkcs10 media type is used, the data is
   a C509CertificateRequest structure.

   IANA has registered the following media type [RFC6838]:

   Type name: application

   Subtype name: cose-c509-pkcs10

   Required parameters: N/A

   Optional parameters: N/A




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   Encoding considerations: binary

   Security considerations: See the Security Considerations section of
   [[this document]].

   Interoperability considerations: N/A

   Published specification: [[this document]]

   Applications that use this media type: Applications that employ COSE
   and C509 Certificate Request.

   Fragment identifier considerations: N/A

   Additional information:

   *  Deprecated alias names for this type: N/A

   *  Magic number(s): TBD9

   *  File extension(s): .c509

   *  Macintosh file type code(s): N/A

   Person & email address to contact for further information:
   iesg@ietf.org

   Intended usage: COMMON

   Restrictions on usage: N/A

   Author: COSE WG

   Change controller: IESG

9.16.  Media Type application/cose-c509-privkey

   When the application/cose-c509-privkey media type is used, the data
   is a C509PrivateKey structure.

   IANA has registered the following media type [RFC6838]:

   Type name: application

   Subtype name: cose-c509-privkey

   Required parameters: N/A




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   Optional parameters: usage

   Encoding considerations: binary

   Security considerations: See the Security Considerations section of
   [[this document]].

   Interoperability considerations: N/A

   Published specification: [[this document]]

   Applications that use this media type: Applications that employ COSE
   and use C509 as a certificate type.

   Fragment identifier considerations: N/A

   Additional information:

   *  Deprecated alias names for this type: N/A

   *  Magic number(s): TBD12

   *  File extension(s): .c509

   *  Macintosh file type code(s): N/A

   Person & email address to contact for further information:
   iesg@ietf.org

   Intended usage: COMMON

   Restrictions on usage: N/A

   Author: COSE WG

   Change controller: IESG

9.17.  Media Type application/cose-c509-pem

   When the application/cose-c509-pem media type is used, the data is a
   C509PEM structure.

   IANA has registered the following media type [RFC6838]:

   Type name: application

   Subtype name: cose-c509-pem




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   Required parameters: N/A

   Optional parameters: usage

   Encoding considerations: binary

   Security considerations: See the Security Considerations section of
   [[this document]].

   Interoperability considerations: N/A

   Published specification: [[this document]]

   Applications that use this media type: Applications that employ COSE
   and use C509 as a certificate type.

   Fragment identifier considerations: N/A

   Additional information:

   *  Deprecated alias names for this type: N/A

   *  Magic number(s): TBD13

   *  File extension(s): .c509

   *  Macintosh file type code(s): N/A

   Person & email address to contact for further information:
   iesg@ietf.org

   Intended usage: COMMON

   Restrictions on usage: N/A

   Author: COSE WG

   Change controller: IESG

9.18.  Media Type application/cose-certhash

   When the application/cose-certhash media type is used, the data is a
   COSE_CertHash structure, see [RFC9360].

   IANA has registered the following media type [RFC6838]:

   Type name: application




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   Subtype name: cose-certhash

   Required parameters: N/A

   Optional parameters: usage

   *  Can be absent to provide no further information about what the
      hash value is calculated over.

   *  Can be set to "c509" to indicate that the hash value is calculated
      over a C509 certificate, see Section 3.4.

   Encoding considerations: binary

   Security considerations: See the Security Considerations section of
   [RFC9360].

   Interoperability considerations: N/A

   Published specification: [[this document]]

   Applications that use this media type: Applications that employ COSE
   and use X.509 or C509 as certificate type.

   Fragment identifier considerations: N/A

   Additional information:

   *  Deprecated alias names for this type: N/A

   *  Magic number(s): N/A

   *  File extension(s): N/A

   *  Macintosh file type code(s): N/A

   Person & email address to contact for further information:
   iesg@ietf.org

   Intended usage: COMMON

   Restrictions on usage: N/A

   Author: COSE WG

   Change controller: IESG





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9.19.  CoAP Content-Formats Registry

   IANA is requested to add media types for "application/cose-
   c509-cert", "application/cose-c509-pkcs10", "application/cose-
   c509-privkey" and "application/cose-c509-pem" to the "CoAP Content-
   Formats" registry under the registry group "Constrained RESTful
   Environments (CoRE) Parameters".  A dedicated Content-Format ID is
   requested for the "application/cose-c509-cert" media type in the case
   when the parameter "usage" is set to "chain", see Section 9.14.

   IANA is requested to add media types for "application/cose-certhash"
   to the "CoAP Content-Formats" registry under the registry group
   "Constrained RESTful Environments (CoRE) Parameters".  A dedicated
   Content-Format ID is requested in the case when the parameter "usage"
   is set to "c509", see Section 9.14.

   IANA is requested to add media types for "application/cbor" to the
   "CoAP Content-Formats" registry under the registry group "Constrained
   RESTful Environments (CoRE) Parameters", in the case when the
   encoding is a CBOR text string containing a URI, see [RFC3986].

+-------------------------------+-----------+-------+-------------------+
| Media Type                    | Encoding  | ID    | Reference         |
+===============================+===========+=======+===================+
| application/cose-c509-cert    | -         |  TBD6 | [[this document]] |
+-------------------------------+-----------+-------+-------------------+
| application/cose-c509-cert    |           |       |                   |
| "usage" = "chain"             | -         | TBD15 | [[this document]] |
+-------------------------------+-----------+-------+-------------------+
| application/cose-c509-pkcs10  | -         |  TBD7 | [[this document]] |
+-------------------------------+-----------+-------+-------------------+
| application/cose-c509-privkey | -         | TBD10 | [[this document]] |
+-------------------------------+-----------+-------+-------------------+
| application/cose-c509-pem     | -         | TBD11 | [[this document]] |
+-------------------------------+-----------+-------+-------------------+
| application/cose-certhash     | -         | TBD16 | [[this document]] |
+-------------------------------+-----------+-------+-------------------+
| application/cose-certhash     |           |       |                   |
| "usage" = "c509"              | -         | TBD17 | [[this document]] |
+-------------------------------+-----------+-------+-------------------+
| application/cbor              |           |       |                   |
| containing a URI              | CBOR text | TBD18 | [RFC9360]         |
+-------------------------------+-----------+-------+-------------------+

                  Figure 19: CoAP Content-Format IDs






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9.20.  TLS Certificate Types Registry

   This document registers the following entry in the "TLS Certificate
   Types" registry under the "Transport Layer Security (TLS) Extensions"
   heading.  The new certificate type can be used with additional TLS
   certificate compression [RFC8879].  C509 is defined in the same way
   as as X.509, but uses a different value and instead of DER-encoded
   X.509 certificate, opaque cert_data<1..2^24-1> contains a the CBOR
   sequence ~C509Certificate (an unwrapped C509Certificate).

   +-------+------------------+-------------+--------------------------+
   | Value | Name             | Recommended | Comment                  |
   +=======+==================+=============+==========================+
   |  TBD5 | C509 Certificate |           Y |                          |
   +-------+------------------+-------------+--------------------------+

9.21.  CBOR Tags Registry

   This document registers the following entries in the "CBOR Tags"
   registry under the "Concise Binary Object Representation (CBOR) Tags"
   heading.

   +------+------------------------------------------------------------+
   |  Tag | X.509 Public Key Algorithms                                |
   +======+============================================================+
   | TBD6 | Data Item: COSE_C509                                       |
   |      | Semantics: An ordered chain of C509 certificates           |
   |      | Reference: This document                                   |
   +------+------------------------------------------------------------+

9.22.  TLSA Selectors Registry

   This document registers the following entries in the "TLSA Selectors"
   registry under the "DNS-Based Authentication of Named Entities (DANE)
   Parameters" heading.

+-------+---------+--------------------------------+-------------------+
| Value | Acronym |    Short Description           |     Reference     |
+=======+=========+================================+===================+
|  TBD7 |    C509 | CBOR encoded PKIX certificates | [[this document]] |
+-------+---------+--------------------------------+-------------------+

   The TLSA selectors registry defined in [RFC6698] originally only
   applied to PKIX [RFC5280] certificates in DER encoding.  This
   specification updates [RFC6698] to accept the use of C509
   certificates, which are essentially CBOR encoded PKIX certificates.





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9.23.  EDHOC Authentication Credential Types Registry

   This document registers the following entry in the "EDHOC
   Authentication Credential Types" registry under the "Ephemeral
   Diffie-Hellman Over COSE (EDHOC)" heading.  This is used to identify
   supported authentication credential type, for example, during
   discovery of EDHOC resources, see [RFC9668].

   +-------+----------------------+-------------------+
   | Value | Description          |     Reference     |
   +=======+======================+===================+
   | TBD14 | C509 certificate     | [[this document]] |
   +-------+----------------------+-------------------+

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC2985]  Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object
              Classes and Attribute Types Version 2.0", RFC 2985,
              DOI 10.17487/RFC2985, November 2000,
              <https://www.rfc-editor.org/rfc/rfc2985>.

   [RFC2986]  Nystrom, M. and B. Kaliski, "PKCS #10: Certification
              Request Syntax Specification Version 1.7", RFC 2986,
              DOI 10.17487/RFC2986, November 2000,
              <https://www.rfc-editor.org/rfc/rfc2986>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/rfc/rfc3986>.

   [RFC4108]  Housley, R., "Using Cryptographic Message Syntax (CMS) to
              Protect Firmware Packages", RFC 4108,
              DOI 10.17487/RFC4108, August 2005,
              <https://www.rfc-editor.org/rfc/rfc4108>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/rfc/rfc5280>.



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   [RFC5958]  Turner, S., "Asymmetric Key Packages", RFC 5958,
              DOI 10.17487/RFC5958, August 2010,
              <https://www.rfc-editor.org/rfc/rfc5958>.

   [RFC6698]  Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
              2012, <https://www.rfc-editor.org/rfc/rfc6698>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/rfc/rfc6838>.

   [RFC6962]  Laurie, B., Langley, A., and E. Kasper, "Certificate
              Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013,
              <https://www.rfc-editor.org/rfc/rfc6962>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/rfc/rfc7030>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [RFC8295]  Turner, S., "EST (Enrollment over Secure Transport)
              Extensions", RFC 8295, DOI 10.17487/RFC8295, January 2018,
              <https://www.rfc-editor.org/rfc/rfc8295>.

   [RFC8610]  Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
              Definition Language (CDDL): A Notational Convention to
              Express Concise Binary Object Representation (CBOR) and
              JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
              June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.

   [RFC8742]  Bormann, C., "Concise Binary Object Representation (CBOR)
              Sequences", RFC 8742, DOI 10.17487/RFC8742, February 2020,
              <https://www.rfc-editor.org/rfc/rfc8742>.

   [RFC8949]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", STD 94, RFC 8949,
              DOI 10.17487/RFC8949, December 2020,
              <https://www.rfc-editor.org/rfc/rfc8949>.






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   [RFC9052]  Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Structures and Process", STD 96, RFC 9052,
              DOI 10.17487/RFC9052, August 2022,
              <https://www.rfc-editor.org/rfc/rfc9052>.

   [RFC9090]  Bormann, C., "Concise Binary Object Representation (CBOR)
              Tags for Object Identifiers", RFC 9090,
              DOI 10.17487/RFC9090, July 2021,
              <https://www.rfc-editor.org/rfc/rfc9090>.

   [RFC9277]  Richardson, M. and C. Bormann, "On Stable Storage for
              Items in Concise Binary Object Representation (CBOR)",
              RFC 9277, DOI 10.17487/RFC9277, August 2022,
              <https://www.rfc-editor.org/rfc/rfc9277>.

   [RFC9360]  Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Header Parameters for Carrying and Referencing X.509
              Certificates", RFC 9360, DOI 10.17487/RFC9360, February
              2023, <https://www.rfc-editor.org/rfc/rfc9360>.

   [RFC9542]  Eastlake 3rd, D., Abley, J., and Y. Li, "IANA
              Considerations and IETF Protocol and Documentation Usage
              for IEEE 802 Parameters", BCP 141, RFC 9542,
              DOI 10.17487/RFC9542, April 2024,
              <https://www.rfc-editor.org/rfc/rfc9542>.

   [RFC9668]  Palombini, F., Tiloca, M., Höglund, R., Hristozov, S., and
              G. Selander, "Using Ephemeral Diffie-Hellman Over COSE
              (EDHOC) with the Constrained Application Protocol (CoAP)
              and Object Security for Constrained RESTful Environments
              (OSCORE)", RFC 9668, DOI 10.17487/RFC9668, November 2024,
              <https://www.rfc-editor.org/rfc/rfc9668>.

   [SECG]     "Elliptic Curve Cryptography, Standards for Efficient
              Cryptography Group, ver. 2", 2009,
              <https://secg.org/sec1-v2.pdf>.

   [X.690]    "ASN.1 encoding rules. Specification of Basic Encoding
              Rules (BER), Canonical Encoding Rules (CER) and
              Distinguished Encoding Rules (DER)", n.d.,
              <https://www.itu.int/rec/T-REC-X.690>.

10.2.  Informative References








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   [CAB-Code] CA/Browser Forum, "CA/Browser Forum, "Baseline
              Requirements for the Issuance and Management of Publicly-
              Trusted Code Signing Certificates Version 3.8.0"", August
              2024, <https://cabforum.org/baseline-requirements-code-
              signing/>.

   [CAB-TLS]  CA/Browser Forum, "CA/Browser Forum, "Baseline
              Requirements for the Issuance and Management of Publicly-
              Trusted Certificates Version 2.1.4"", March 2025,
              <https://cabforum.org/baseline-requirements-documents/>.

   [CborMe]   Bormann, C., "CBOR Playground", May 2018,
              <https://cbor.me/>.

   [GSMA-eUICC]
              GSMA, "GSMA eUICC PKI Certificate Policy Version 2.2",
              January 2025, <https://www.gsma.com/solutions-and-
              impact/technologies/esim/wp-content/uploads/2025/01/
              SGP.14-v2.2.pdf>.

   [I-D.ietf-lamps-rfc7030-csrattrs]
              Richardson, M., Friel, O., von Oheimb, D., and D. Harkins,
              "Clarification and enhancement of RFC7030 CSR Attributes
              definition", Work in Progress, Internet-Draft, draft-ietf-
              lamps-rfc7030-csrattrs-22, 8 May 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-lamps-
              rfc7030-csrattrs-22>.

   [I-D.ietf-tls-ctls]
              Rescorla, E., Barnes, R., Tschofenig, H., and B. M.
              Schwartz, "Compact TLS 1.3", Work in Progress, Internet-
              Draft, draft-ietf-tls-ctls-10, 17 April 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-tls-
              ctls-10>.

   [I-D.ietf-uta-tls13-iot-profile]
              Tschofenig, H., Fossati, T., and M. Richardson, "TLS/DTLS
              1.3 Profiles for the Internet of Things", Work in
              Progress, Internet-Draft, draft-ietf-uta-tls13-iot-
              profile-14, 5 May 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-uta-
              tls13-iot-profile-14>.









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   [IEEE-802.1AR]
              Institute of Electrical and Electronics Engineers, "IEEE
              Standard for Local and metropolitan area networks–Secure
              Device Identity", IEEE Standard 802.1AR-2018 , August
              2018,
              <https://standards.ieee.org/standard/802_1AR-2018.html>.

   [RFC6487]  Huston, G., Michaelson, G., and R. Loomans, "A Profile for
              X.509 PKIX Resource Certificates", RFC 6487,
              DOI 10.17487/RFC6487, February 2012,
              <https://www.rfc-editor.org/rfc/rfc6487>.

   [RFC6955]  Schaad, J. and H. Prafullchandra, "Diffie-Hellman Proof-
              of-Possession Algorithms", RFC 6955, DOI 10.17487/RFC6955,
              May 2013, <https://www.rfc-editor.org/rfc/rfc6955>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <https://www.rfc-editor.org/rfc/rfc7228>.

   [RFC7468]  Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
              PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
              April 2015, <https://www.rfc-editor.org/rfc/rfc7468>.

   [RFC7925]  Tschofenig, H., Ed. and T. Fossati, "Transport Layer
              Security (TLS) / Datagram Transport Layer Security (DTLS)
              Profiles for the Internet of Things", RFC 7925,
              DOI 10.17487/RFC7925, July 2016,
              <https://www.rfc-editor.org/rfc/rfc7925>.

   [RFC7932]  Alakuijala, J. and Z. Szabadka, "Brotli Compressed Data
              Format", RFC 7932, DOI 10.17487/RFC7932, July 2016,
              <https://www.rfc-editor.org/rfc/rfc7932>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/rfc/rfc8446>.

   [RFC8603]  Jenkins, M. and L. Zieglar, "Commercial National Security
              Algorithm (CNSA) Suite Certificate and Certificate
              Revocation List (CRL) Profile", RFC 8603,
              DOI 10.17487/RFC8603, May 2019,
              <https://www.rfc-editor.org/rfc/rfc8603>.

   [RFC8879]  Ghedini, A. and V. Vasiliev, "TLS Certificate
              Compression", RFC 8879, DOI 10.17487/RFC8879, December
              2020, <https://www.rfc-editor.org/rfc/rfc8879>.



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   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/rfc/rfc9000>.

   [RFC9147]  Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
              <https://www.rfc-editor.org/rfc/rfc9147>.

   [RFC9148]  van der Stok, P., Kampanakis, P., Richardson, M., and S.
              Raza, "EST-coaps: Enrollment over Secure Transport with
              the Secure Constrained Application Protocol", RFC 9148,
              DOI 10.17487/RFC9148, April 2022,
              <https://www.rfc-editor.org/rfc/rfc9148>.

   [RFC9190]  Preuß Mattsson, J. and M. Sethi, "EAP-TLS 1.3: Using the
              Extensible Authentication Protocol with TLS 1.3",
              RFC 9190, DOI 10.17487/RFC9190, February 2022,
              <https://www.rfc-editor.org/rfc/rfc9190>.

   [RFC9191]  Sethi, M., Preuß Mattsson, J., and S. Turner, "Handling
              Large Certificates and Long Certificate Chains in TLS-
              Based EAP Methods", RFC 9191, DOI 10.17487/RFC9191,
              February 2022, <https://www.rfc-editor.org/rfc/rfc9191>.

   [RFC9528]  Selander, G., Preuß Mattsson, J., and F. Palombini,
              "Ephemeral Diffie-Hellman Over COSE (EDHOC)", RFC 9528,
              DOI 10.17487/RFC9528, March 2024,
              <https://www.rfc-editor.org/rfc/rfc9528>.

   [SP-800-56A]
              Barker, E., Chen, L., Roginsky, A., Vassilev, A., and R.
              Davis, "Recommendation for Pair-Wise Key-Establishment
              Schemes Using Discrete Logarithm Cryptography",
              NIST Special Publication 800-56A Revision 3, April 2018,
              <https://doi.org/10.6028/NIST.SP.800-56Ar3>.

   [X.509-IoT]
              Forsby, F., Furuhed, M., Papadimitratos, P., and S. Raza,
              "Lightweight X.509 Digital Certificates for the Internet
              of Things.", Springer, Cham. Lecture Notes of the
              Institute for Computer Sciences, Social Informatics and
              Telecommunications Engineering, vol 242., July 2018,
              <https://doi.org/10.1007/978-3-319-93797-7_14>.

Appendix A.  C509 Certificate Examples




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A.1.  Example: RFC 7925 profiled X.509 Certificate

   Example of [RFC7925] profiled X.509 certificate parsed with OpenSSL.

   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 128269 (0x1f50d)
           Signature Algorithm: ecdsa-with-SHA256
           Issuer: CN=RFC test CA
           Validity
               Not Before: Jan  1 00:00:00 2023 GMT
               Not After : Jan  1 00:00:00 2026 GMT
           Subject: CN=01-23-45-FF-FE-67-89-AB
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (256 bit)
                   pub:
                       04:b1:21:6a:b9:6e:5b:3b:33:40:f5:bd:f0:2e:69:
                       3f:16:21:3a:04:52:5e:d4:44:50:b1:01:9c:2d:fd:
                       38:38:ab:ac:4e:14:d8:6c:09:83:ed:5e:9e:ef:24:
                       48:c6:86:1c:c4:06:54:71:77:e6:02:60:30:d0:51:
                       f7:79:2a:c2:06
                   ASN1 OID: prime256v1
                   NIST CURVE: P-256
           X509v3 extensions:
               X509v3 Key Usage:
                   Digital Signature
       Signature Algorithm: ecdsa-with-SHA256
           30:46:02:21:00:d4:32:0b:1d:68:49:e3:09:21:9d:30:03:7e:
           13:81:66:f2:50:82:47:dd:da:e7:6c:ce:ea:55:05:3c:10:8e:
           90:02:21:00:d5:51:f6:d6:01:06:f1:ab:b4:84:cf:be:62:56:
           c1:78:e4:ac:33:14:ea:19:19:1e:8b:60:7d:a5:ae:3b:da:16

   The DER encoding of the above certificate is 316 bytes.
















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   30 82 01 38 30 81 de a0 03 02 01 02 02 03 01 f5 0d 30 0a 06 08 2a 86
   48 ce 3d 04 03 02 30 16 31 14 30 12 06 03 55 04 03 0c 0b 52 46 43 20
   74 65 73 74 20 43 41 30 1e 17 0d 32 33 30 31 30 31 30 30 30 30 30 30
   5a 17 0d 32 36 30 31 30 31 30 30 30 30 30 30 5a 30 22 31 20 30 1e 06
   03 55 04 03 0c 17 30 31 2d 32 33 2d 34 35 2d 46 46 2d 46 45 2d 36 37
   2d 38 39 2d 41 42 30 59 30 13 06 07 2a 86 48 ce 3d 02 01 06 08 2a 86
   48 ce 3d 03 01 07 03 42 00 04 b1 21 6a b9 6e 5b 3b 33 40 f5 bd f0 2e
   69 3f 16 21 3a 04 52 5e d4 44 50 b1 01 9c 2d fd 38 38 ab ac 4e 14 d8
   6c 09 83 ed 5e 9e ef 24 48 c6 86 1c c4 06 54 71 77 e6 02 60 30 d0 51
   f7 79 2a c2 06 a3 0f 30 0d 30 0b 06 03 55 1d 0f 04 04 03 02 07 80 30
   0a 06 08 2a 86 48 ce 3d 04 03 02 03 49 00 30 46 02 21 00 d4 32 0b 1d
   68 49 e3 09 21 9d 30 03 7e 13 81 66 f2 50 82 47 dd da e7 6c ce ea 55
   05 3c 10 8e 90 02 21 00 d5 51 f6 d6 01 06 f1 ab b4 84 cf be 62 56 c1
   78 e4 ac 33 14 ea 19 19 1e 8b 60 7d a5 ae 3b da 16

A.1.1.  Example: C509 Certificate Encoding

   This section shows the C509 encoding of the X.509 certificate in the
   previous section.  The point compressed public key is represented as
   described in Section 3.2.1.

   Figure 20 shows the diagnostic notation of the unwrapped CBOR
   sequence, ~C509Certificate, see Section 3.1.

   /This defines a CBOR Sequence (RFC 8742):/

     3,                   / version and certificate type /
     h'01f50d',           / serialNumber /
     0,                   / signatureAlgorithm /
     "RFC test CA",       / issuer /
     1672531200,          / notBefore /
     1767225600,          / notAfter /
     48(h'0123456789AB'), / subject, EUI-64 /
     1,                   / subjectPublicKeyAlgorithm /
     h'FEB1216AB96E5B3B3340F5BDF02E693F16213A04525ED44450
       B1019C2DFD3838AB',
     1,                   / single extension:
                            non-critical keyUsage
                            digitalSignature /
     h'D4320B1D6849E309219D30037E138166F2508247DDDAE76CCE
       EA55053C108E90D551F6D60106F1ABB484CFBE6256C178E4AC
       3314EA19191E8B607DA5AE3BDA16'

          Figure 20: CBOR diagnostic notation of ~C509Certificate

   Figure 21 shows the plain hex format of the unwrapped CBOR sequence,
   the size is 140 bytes.




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   03
   43 01 F5 0D
   00
   6B 52 46 43 20 74 65 73 74 20 43 41
   1A 63 B0 CD 00
   1A 69 55 B9 00
   D8 30 46 01 23 45 67 89 AB
   01
   58 21 FE B1 21 6A B9 6E 5B 3B 33 40 F5 BD F0 2E 69 3F 16 21 3A 04 52
   5E D4 44 50 B1 01 9C 2D FD 38 38 AB
   01
   58 40 D4 32 0B 1D 68 49 E3 09 21 9D 30 03 7E 13 81 66 F2 50 82 47 DD
   DA E7 6C CE EA 55 05 3C 10 8E 90 D5 51 F6 D6 01 06 F1 AB B4 84 CF BE
   62 56 C1 78 E4 AC 33 14 EA 19 19 1E 8B 60 7D A5 AE 3B DA 16

           Figure 21: CBOR plain hex format of ~C509Certificate.

A.1.2.  Example: Natively Signed C509 Certificate

   This section shows the natively signed C509 certificate corresponding
   to that of the previous section, which is identical except for
   c509CertificateType, encoding of point compression (see
   Section 3.2.1), and signatureValue.

   Figure 22 shows the diagnostic notation of the natively signed
   unwrapped CBOR sequence, ~C509Certificate.

   /This defines a CBOR Sequence (RFC 8742):/

     2,
     h'01f50d',
     0,
     "RFC test CA",
     1672531200,
     1767225600,
     48(h'0123456789AB'),
     1,
     h'02B1216AB96E5B3B3340F5BDF02E693F16213A04525ED44450
       B1019C2DFD3838AB',
     1,
     h'EB0D472731F689BC00F5880B12C68B3F9FD38B23FADFCA2095
       0F3F241B60A202579CAC28CD3B7494D5FA5D8BBAB4600357E5
       50AB9FA9A65D9BA2B3B82E668CC6'

          Figure 22: CBOR diagnostic notation of ~C509Certificate

   Figure 23 shows the plain hex format of the natively signed unwrapped
   CBOR sequence, the size is 140 bytes.



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   02
   43 01 F5 0D
   00
   6B 52 46 43 20 74 65 73 74 20 43 41
   1A 63 B0 CD 00
   1A 69 55 B9 00
   D8 30 46 01 23 45 67 89 AB
   01
   58 21 02 B1 21 6A B9 6E 5B 3B 33 40 F5 BD F0 2E 69 3F 16 21 3A 04 52
   5E D4 44 50 B1 01 9C 2D FD 38 38 AB
   01
   58 40 EB 0D 47 27 31 F6 89 BC 00 F5 88 0B 12 C6 8B 3F 9F D3 8B 23 FA
   DF CA 20 95 0F 3F 24 1B 60 A2 02 57 9C AC 28 CD 3B 74 94 D5 FA 5D 8B
   BA B4 60 03 57 E5 50 AB 9F A9 A6 5D 9B A2 B3 B8 2E 66 8C C6

           Figure 23: CBOR plain hex format of ~C509Certificate.

A.1.3.  C509 for Diffie-Hellman keys

   The two previous examples illustrate the common key usage
   digitalSignature.  A C509 certificate for a public Diffie-Hellman key
   would instead have key usage keyAgreement encoded according to
   Section 3.3 (in this case of single extension encoded as integer 16
   instead of 1 for digital signature) but otherwise identical in
   format.  Note that Section 5.6.3.2 of [SP-800-56A] allows a key
   agreement key pair to be used to sign a certificate request.

A.1.4.  Example: Additional Keys for the Example Certificates

   Below are the issuer key pair and the subject private key belonging
   to the above example certificates.  The private keys are encoded as
   in COSE [RFC9052].  These issuer key pair can be used to sign or
   verify the example certificates and the subject private key allows
   the example certificates to be used in test vectors for other
   protocols like EDHOC.

   issuerPublicKeyAlgorithm :
   1 (EC Public Key (Weierstraß) with secp256r1)

   issuerPublicKey :
   h'02AE4CDB01F614DEFC7121285FDC7F5C6D1D42C95647F061BA0080DF678867845E'

   issuerPrivateKey :
   h'DC66B3415456D649429B53223DF7532B942D6B0E0842C30BCA4C0ACF91547BB2'

   subjectPrivateKey :
   h'D718111F3F9BD91B92FF6877F386BDBFCEA7154268FD7F2FB56EE17D99EA16D4'




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A.1.5.  Examples: C509Certificate and C509CertData

   This section examplifies other CBOR objects defined in this
   specification, based on the natively signed C509 certificate in
   Appendix A.1.2.

   Figure 24 shows the encoding of the corresponding C509Certificate,
   i.e. the CBOR array wrapping of the CBOR sequence ~C509Certificate,
   see Section 3.1.

   8B
   02
   43 01 F5 0D
   00
   6B 52 46 43 20 74 65 73 74 20 43 41
   1A 63 B0 CD 00
   1A 69 55 B9 00
   D8 30 46 01 23 45 67 89 AB
   01
   58 21 02 B1 21 6A B9 6E 5B 3B 33 40 F5 BD F0 2E 69 3F 16 21 3A 04 52
   5E D4 44 50 B1 01 9C 2D FD 38 38 AB
   01
   58 40 EB 0D 47 27 31 F6 89 BC 00 F5 88 0B 12 C6 8B 3F 9F D3 8B 23 FA
   DF CA 20 95 0F 3F 24 1B 60 A2 02 57 9C AC 28 CD 3B 74 94 D5 FA 5D 8B
   BA B4 60 03 57 E5 50 AB 9F A9 A6 5D 9B A2 B3 B8 2E 66 8C C6

           Figure 24: C509Certificate: The CBOR array wrapping of
                              ~C509Certificate

   Note that C509Certificate is identical to ~C509Certificate in
   Appendix A.1.2 except for the prefix 8B (which indicates that it is a
   CBOR array with 11 elements).

   Figure 25 shows the encoding of the corresponding C509CertData, i.e.
   the CBOR byte string wrapping of the CBOR sequence ~C509Certificate,
   see Section 3.4.















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   58 8C
   02
   43 01 F5 0D
   00
   6B 52 46 43 20 74 65 73 74 20 43 41
   1A 63 B0 CD 00
   1A 69 55 B9 00
   D8 30 46 01 23 45 67 89 AB
   01
   58 21 02 B1 21 6A B9 6E 5B 3B 33 40 F5 BD F0 2E 69 3F 16 21 3A 04 52
   5E D4 44 50 B1 01 9C 2D FD 38 38 AB
   01
   58 40 EB 0D 47 27 31 F6 89 BC 00 F5 88 0B 12 C6 8B 3F 9F D3 8B 23 FA
   DF CA 20 95 0F 3F 24 1B 60 A2 02 57 9C AC 28 CD 3B 74 94 D5 FA 5D 8B
   BA B4 60 03 57 E5 50 AB 9F A9 A6 5D 9B A2 B3 B8 2E 66 8C C6

           Figure 25: C509CertData: CBOR byte string wrapping of
                             ~C509Certificate.

   Note that C509CertData is identical to ~C509Certificate in
   Appendix A.1.2 except for the prefix 58 8C (which indicates that it
   is a CBOR byte string of 140 bytes).

A.2.  Example: IEEE 802.1AR profiled X.509 Certificate

   An example of an IEEE 802.1AR profiled X.509 certificate (Secure
   Device Identifier, DevID) is provided in Appendix C.2 of [RFC9148].
   The certificate is shown below including details of the
   hardwareModuleName type of otherName in subjectAltName, see
   Section 3.3.





















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Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 9112578475118446130 (0x7e7661d7b54e4632)
        Signature Algorithm: ecdsa-with-SHA256
        Issuer: C=US, ST=CA, O=Example Inc, OU=certification, CN=802.1AR CA
        Validity
            Not Before: Jan 31 11:29:16 2019 GMT
            Not After : Dec 31 23:59:59 9999 GMT
        Subject: C=US, ST=CA, L=LA, O=example Inc, OU=IoT/serialNumber=Wt1234
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
                Public-Key: (256 bit)
                pub:
                    04:c8:b4:21:f1:1c:25:e4:7e:3a:c5:71:23:bf:2d:
                    9f:dc:49:4f:02:8b:c3:51:cc:80:c0:3f:15:0b:f5:
                    0c:ff:95:8d:75:41:9d:81:a6:a2:45:df:fa:e7:90:
                    be:95:cf:75:f6:02:f9:15:26:18:f8:16:a2:b2:3b:
                    56:38:e5:9f:d9
                ASN1 OID: prime256v1
                NIST CURVE: P-256
        X509v3 extensions:
            X509v3 Basic Constraints:
                CA:FALSE
            X509v3 Subject Key Identifier:
                96:60:0D:87:16:BF:7F:D0:E7:52:D0:AC:76:07:77:AD:66:5D:02:A0
            X509v3 Authority Key Identifier:
                68:D1:65:51:F9:51:BF:C8:2A:43:1D:0D:9F:08:BC:2D:20:5B:11:60
            X509v3 Key Usage: critical
                Digital Signature, Key Encipherment
            X509v3 Subject Alternative Name:
                otherName:
                    type-id: 1.3.6.1.5.5.7.8.4 (id-on-hardwareModuleName)
                    value:
                        hwType: 1.3.6.1.4.1.6715.10.1
                        hwSerialNum: 01:02:03:04
    Signature Algorithm: ecdsa-with-SHA256
    Signature Value:
        30:46:02:21:00:c0:d8:19:96:d2:50:7d:69:3f:3c:48:ea:a5:
        ee:94:91:bd:a6:db:21:40:99:d9:81:17:c6:3b:36:13:74:cd:
        86:02:21:00:a7:74:98:9f:4c:32:1a:5c:f2:5d:83:2a:4d:33:
        6a:08:ad:67:df:20:f1:50:64:21:18:8a:0a:de:6d:34:92:36

   The DER encoding of the certificate is 577 bytes:







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   30 82 02 3D 30 82 01 E2 A0 03 02 01 02 02 08 7E 76 61 D7 B5 4E 46 32
   30 0A 06 08 2A 86 48 CE 3D 04 03 02 30 5D 31 0B 30 09 06 03 55 04 06
   13 02 55 53 31 0B 30 09 06 03 55 04 08 0C 02 43 41 31 14 30 12 06 03
   55 04 0A 0C 0B 45 78 61 6D 70 6C 65 20 49 6E 63 31 16 30 14 06 03 55
   04 0B 0C 0D 63 65 72 74 69 66 69 63 61 74 69 6F 6E 31 13 30 11 06 03
   55 04 03 0C 0A 38 30 32 2E 31 41 52 20 43 41 30 20 17 0D 31 39 30 31
   33 31 31 31 32 39 31 36 5A 18 0F 39 39 39 39 31 32 33 31 32 33 35 39
   35 39 5A 30 5C 31 0B 30 09 06 03 55 04 06 13 02 55 53 31 0B 30 09 06
   03 55 04 08 0C 02 43 41 31 0B 30 09 06 03 55 04 07 0C 02 4C 41 31 14
   30 12 06 03 55 04 0A 0C 0B 65 78 61 6D 70 6C 65 20 49 6E 63 31 0C 30
   0A 06 03 55 04 0B 0C 03 49 6F 54 31 0F 30 0D 06 03 55 04 05 13 06 57
   74 31 32 33 34 30 59 30 13 06 07 2A 86 48 CE 3D 02 01 06 08 2A 86 48
   CE 3D 03 01 07 03 42 00 04 C8 B4 21 F1 1C 25 E4 7E 3A C5 71 23 BF 2D
   9F DC 49 4F 02 8B C3 51 CC 80 C0 3F 15 0B F5 0C FF 95 8D 75 41 9D 81
   A6 A2 45 DF FA E7 90 BE 95 CF 75 F6 02 F9 15 26 18 F8 16 A2 B2 3B 56
   38 E5 9F D9 A3 81 8A 30 81 87 30 09 06 03 55 1D 13 04 02 30 00 30 1D
   06 03 55 1D 0E 04 16 04 14 96 60 0D 87 16 BF 7F D0 E7 52 D0 AC 76 07
   77 AD 66 5D 02 A0 30 1F 06 03 55 1D 23 04 18 30 16 80 14 68 D1 65 51
   F9 51 BF C8 2A 43 1D 0D 9F 08 BC 2D 20 5B 11 60 30 0E 06 03 55 1D 0F
   01 01 FF 04 04 03 02 05 A0 30 2A 06 03 55 1D 11 04 23 30 21 A0 1F 06
   08 2B 06 01 05 05 07 08 04 A0 13 30 11 06 09 2B 06 01 04 01 B4 3B 0A
   01 04 04 01 02 03 04 30 0A 06 08 2A 86 48 CE 3D 04 03 02 03 49 00 30
   46 02 21 00 C0 D8 19 96 D2 50 7D 69 3F 3C 48 EA A5 EE 94 91 BD A6 DB
   21 40 99 D9 81 17 C6 3B 36 13 74 CD 86 02 21 00 A7 74 98 9F 4C 32 1A
   5C F2 5D 83 2A 4D 33 6A 08 AD 67 DF 20 F1 50 64 21 18 8A 0A DE 6D 34
   92 36

A.2.1.  Example: C509 Certificate Encoding

   The CBOR encoding (~C509Certificate) of the same X.509 certificate is
   shown below in CBOR diagnostic format.




















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 /This defines a CBOR Sequence (RFC 8742):/

  3,
  h'7E7661D7B54E4632',
  0,
  [
   -4, "US",
    6, "CA",
    8, "Example Inc",
    9, "certification",
    1, "802.1AR CA"
  ],
  1548934156,
  null,
  [
   -4, "US",
    6, "CA",
    5, "LA",
    8, "example Inc",
    9, "IoT",
   -3, "Wt1234"
  ],
  1,
  h'FDC8B421F11C25E47E3AC57123BF2D9FDC494F028BC351CC80C03F150BF50CFF95',
  [
    4, -2,
    1, h'96600D8716BF7FD0E752D0AC760777AD665D02A0',
    7, h'68D16551F951BFC82A431D0D9F08BC2D205B1160',
   -2, 5,
   3, [-1, [h'2B06010401B43B0A01', h'01020304']]
      / subjectAltName with hardwareModuleName /
  ],
  h'C0D81996D2507D693F3C48EAA5EE9491BDA6DB214099D98117C63B361374CD86A7
    74989F4C321A5CF25D832A4D336A08AD67DF20F1506421188A0ADE6D349236'

   The size of the CBOR encoding (CBOR sequence) is 275 bytes:















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   03 48 7E 76 61 D7 B5 4E 46 32 8A 23 62 55 53 06 62 43 41 08 6B 45 78
   61 6D 70 6C 65 20 49 6E 63 09 6D 63 65 72 74 69 66 69 63 61 74 69 6F
   6E 01 6A 38 30 32 2E 31 41 52 20 43 41 1A 5C 52 DC 0C F6 8C 23 62 55
   53 06 62 43 41 05 62 4C 41 08 6B 65 78 61 6D 70 6C 65 20 49 6E 63 09
   63 49 6F 54 22 66 57 74 31 32 33 34 01 58 21 FD C8 B4 21 F1 1C 25 E4
   7E 3A C5 71 23 BF 2D 9F DC 49 4F 02 8B C3 51 CC 80 C0 3F 15 0B F5 0C
   FF 95 8A 04 21 01 54 96 60 0D 87 16 BF 7F D0 E7 52 D0 AC 76 07 77 AD
   66 5D 02 A0 07 54 68 D1 65 51 F9 51 BF C8 2A 43 1D 0D 9F 08 BC 2D 20
   5B 11 60 21 05 03 82 20 82 49 2B 06 01 04 01 B4 3B 0A 01 44 01 02 03
   04 00 58 40 C0 D8 19 96 D2 50 7D 69 3F 3C 48 EA A5 EE 94 91 BD A6 DB
   21 40 99 D9 81 17 C6 3B 36 13 74 CD 86 A7 74 98 9F 4C 32 1A 5C F2 5D
   83 2A 4D 33 6A 08 AD 67 DF 20 F1 50 64 21 18 8A 0A DE 6D 34 92 36

A.3.  Example: CAB Baseline ECDSA HTTPS X.509 Certificate

   The www.ietf.org HTTPS server replies with a certificate message with
   2 certificates.  The DER encoding of the first certificate is 1209
   bytes.

   30 82 04 b5 30 82 04 5a a0 03 02 01 02 02 10 04 7f a1 e3 19 28 ee 40
   3b a0 b8 3a 39 56 73 fc 30 0a 06 08 2a 86 48 ce 3d 04 03 02 30 4a 31
   0b 30 09 06 03 55 04 06 13 02 55 53 31 19 30 17 06 03 55 04 0a 13 10
   43 6c 6f 75 64 66 6c 61 72 65 2c 20 49 6e 63 2e 31 20 30 1e 06 03 55
   04 03 13 17 43 6c 6f 75 64 66 6c 61 72 65 20 49 6e 63 20 45 43 43 20
   43 41 2d 33 30 1e 17 0d 32 30 30 37 32 39 30 30 30 30 30 30 5a 17 0d
   32 31 30 37 32 39 31 32 30 30 30 30 5a 30 6d 31 0b 30 09 06 03 55 04
   06 13 02 55 53 31 0b 30 09 06 03 55 04 08 13 02 43 41 31 16 30 14 06
   03 55 04 07 13 0d 53 61 6e 20 46 72 61 6e 63 69 73 63 6f 31 19 30 17
   06 03 55 04 0a 13 10 43 6c 6f 75 64 66 6c 61 72 65 2c 20 49 6e 63 2e
   31 1e 30 1c 06 03 55 04 03 13 15 73 6e 69 2e 63 6c 6f 75 64 66 6c 61
   72 65 73 73 6c 2e 63 6f 6d 30 59 30 13 06 07 2a 86 48 ce 3d 02 01 06
   08 2a 86 48 ce 3d 03 01 07 03 42 00 04 96 3e cd d8 4d cd 1b 93 a1 cf
   43 2d 1a 72 17 d6 c6 3b de 33 55 a0 2f 8c fb 5a d8 99 4c d4 4e 20 5f
   15 f6 e3 d2 3b 38 2b a6 49 9b b1 7f 34 1f a5 92 fa 21 86 1f 16 d3 12
   06 63 24 05 fd 70 42 bd a3 82 02 fd 30 82 02 f9 30 1f 06 03 55 1d 23
   04 18 30 16 80 14 a5 ce 37 ea eb b0 75 0e 94 67 88 b4 45 fa d9 24 10
   87 96 1f 30 1d 06 03 55 1d 0e 04 16 04 14 cc 0b 50 e7 d8 37 db f2 43
   f3 85 3d 48 60 f5 3b 39 be 9b 2a 30 2e 06 03 55 1d 11 04 27 30 25 82
   15 73 6e 69 2e 63 6c 6f 75 64 66 6c 61 72 65 73 73 6c 2e 63 6f 6d 82
   0c 77 77 77 2e 69 65 74 66 2e 6f 72 67 30 0e 06 03 55 1d 0f 01 01 ff
   04 04 03 02 07 80 30 1d 06 03 55 1d 25 04 16 30 14 06 08 2b 06 01 05
   05 07 03 01 06 08 2b 06 01 05 05 07 03 02 30 7b 06 03 55 1d 1f 04 74
   30 72 30 37 a0 35 a0 33 86 31 68 74 74 70 3a 2f 2f 63 72 6c 33 2e 64
   69 67 69 63 65 72 74 2e 63 6f 6d 2f 43 6c 6f 75 64 66 6c 61 72 65 49
   6e 63 45 43 43 43 41 2d 33 2e 63 72 6c 30 37 a0 35 a0 33 86 31 68 74
   74 70 3a 2f 2f 63 72 6c 34 2e 64 69 67 69 63 65 72 74 2e 63 6f 6d 2f
   43 6c 6f 75 64 66 6c 61 72 65 49 6e 63 45 43 43 43 41 2d 33 2e 63 72
   6c 30 4c 06 03 55 1d 20 04 45 30 43 30 37 06 09 60 86 48 01 86 fd 6c



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   01 01 30 2a 30 28 06 08 2b 06 01 05 05 07 02 01 16 1c 68 74 74 70 73
   3a 2f 2f 77 77 77 2e 64 69 67 69 63 65 72 74 2e 63 6f 6d 2f 43 50 53
   30 08 06 06 67 81 0c 01 02 02 30 76 06 08 2b 06 01 05 05 07 01 01 04
   6a 30 68 30 24 06 08 2b 06 01 05 05 07 30 01 86 18 68 74 74 70 3a 2f
   2f 6f 63 73 70 2e 64 69 67 69 63 65 72 74 2e 63 6f 6d 30 40 06 08 2b
   06 01 05 05 07 30 02 86 34 68 74 74 70 3a 2f 2f 63 61 63 65 72 74 73
   2e 64 69 67 69 63 65 72 74 2e 63 6f 6d 2f 43 6c 6f 75 64 66 6c 61 72
   65 49 6e 63 45 43 43 43 41 2d 33 2e 63 72 74 30 0c 06 03 55 1d 13 01
   01 ff 04 02 30 00 30 82 01 05 06 0a 2b 06 01 04 01 d6 79 02 04 02 04
   81 f6 04 81 f3 00 f1 00 76 00 f6 5c 94 2f d1 77 30 22 14 54 18 08 30
   94 56 8e e3 4d 13 19 33 bf df 0c 2f 20 0b cc 4e f1 64 e3 00 00 01 73
   9c 83 5f 8e 00 00 04 03 00 47 30 45 02 21 00 f8 d1 b4 a9 3d 2f 0d 4c
   41 76 df b4 88 bc c7 3b 86 44 3d 7d e0 0e 6a c8 17 4d 89 48 a8 84 36
   68 02 20 29 ff 5a 34 06 8a 24 0c 69 50 27 88 e8 ee 25 ab 7e d2 cb cf
   68 6e ce 7b 5f 96 b4 31 a9 07 02 fa 00 77 00 5c dc 43 92 fe e6 ab 45
   44 b1 5e 9a d4 56 e6 10 37 fb d5 fa 47 dc a1 73 94 b2 5e e6 f6 c7 0e
   ca 00 00 01 73 9c 83 5f be 00 00 04 03 00 48 30 46 02 21 00 e8 91 c1
   97 bf b0 e3 d3 0c b6 ce e6 0d 94 c3 c7 5f d1 17 53 36 93 11 08 d8 98
   12 d4 d2 9d 81 d0 02 21 00 a1 59 d1 6c 46 47 d1 48 37 57 fc d6 ce 4e
   75 ec 7b 5e f6 57 ef e0 28 f8 e5 cc 47 92 68 2d ac 43 30 0a 06 08 2a
   86 48 ce 3d 04 03 02 03 49 00 30 46 02 21 00 bd 63 cf 4f 7e 5c fe 6c
   29 38 5e a7 1c fb fc 1e 3f 7b 1c d0 72 51 a2 21 f7 77 69 c0 f4 71 df
   ea 02 21 00 b5 c0 6c c4 58 54 fa 30 b2 82 88 b1 d3 bb 9a 66 61 ed 50
   31 72 5b 1a 82 02 e0 da 5b 59 f9 54 02

A.3.1.  Example: C509 Certificate Encoding

   The CBOR encoding (~C509Certificate) of the first X.509 certificate
   is shown below in CBOR diagnostic format.

/This defines a CBOR Sequence (RFC 8742):/

3,
h'047FA1E31928EE403BA0B83A395673FC',
0,
[
 -4, "US",
 -8, "Cloudflare, Inc.",
 -1, "Cloudflare Inc ECC CA-3"
],
1595980800,
1627560000,
[
 -4, "US",
 -6, "CA",
 -5, "San Francisco",
 -8, "Cloudflare, Inc.",
 -1, "sni.cloudflaressl.com"



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],
1,
h'FD963ECDD84DCD1B93A1CF432D1A7217D6C63BDE3355A02F8CFB5AD8994CD44E20',
[
 7, h'A5CE37EAEBB0750E946788B445FAD9241087961F',
 1, h'CC0B50E7D837DBF243F3853D4860F53B39BE9B2A',
 3, [2, "sni.cloudflaressl.com", 2, "www.ietf.org"],
-2, 1,
 8, [1, 2],
 5, ["http://crl3.digicert.com/CloudflareIncECCCA-3.crl",
     "http://crl4.digicert.com/CloudflareIncECCCA-3.crl"],
 6, [h'6086480186FD6C0101', [1, "https://www.digicert.com/CPS"],  2],
 9, [1, "http://ocsp.digicert.com",
     2, "http://cacerts.digicert.com/CloudflareIncECCCA-3.crt"],
-4, -2,
10, [
    h'F65C942FD1773022145418083094568EE34D131933BFDF0C2F200BCC4EF164E3',
    77922190,
    0,
    h'F8D1B4A93D2F0D4C4176DFB488BCC73B86443D7DE00E6AC8174D8948A8843668
    29FF5A34068A240C69502788E8EE25AB7ED2CBCF686ECE7B5F96B431A90702FA',
    h'5CDC4392FEE6AB4544B15E9AD456E61037FBD5FA47DCA17394B25EE6F6C70ECA',
    77922238,
    0,
    h'E891C197BFB0E3D30CB6CEE60D94C3C75FD1175336931108D89812D4D29D81D0
    A159D16C4647D1483757FCD6CE4E75EC7B5EF657EFE028F8E5CC4792682DAC43'
    ]
],
h'BD63CF4F7E5CFE6C29385EA71CFBFC1E3F7B1CD07251A221F77769C0F471DFEA
  B5C06CC45854FA30B28288B1D3BB9A6661ED5031725B1A8202E0DA5B59F95402'

   The size of the CBOR encoding (CBOR sequence) is 783 bytes.

A.4.  Example: CAB Baseline RSA HTTPS X.509 Certificate

   The tools.ietf.org HTTPS server replies with a certificate message
   with 4 certificates.  The DER encoding of the first certificate is
   1647 bytes.

   30 82 06 6b 30 82 05 53 a0 03 02 01 02 02 09 00 a6 a5 5c 87 0e 39 b4
   0e 30 0d 06 09 2a 86 48 86 f7 0d 01 01 0b 05 00 30 81 c6 31 0b 30 09
   06 03 55 04 06 13 02 55 53 31 10 30 0e 06 03 55 04 08 13 07 41 72 69
   7a 6f 6e 61 31 13 30 11 06 03 55 04 07 13 0a 53 63 6f 74 74 73 64 61
   6c 65 31 25 30 23 06 03 55 04 0a 13 1c 53 74 61 72 66 69 65 6c 64 20
   54 65 63 68 6e 6f 6c 6f 67 69 65 73 2c 20 49 6e 63 2e 31 33 30 31 06
   03 55 04 0b 13 2a 68 74 74 70 3a 2f 2f 63 65 72 74 73 2e 73 74 61 72
   66 69 65 6c 64 74 65 63 68 2e 63 6f 6d 2f 72 65 70 6f 73 69 74 6f 72
   79 2f 31 34 30 32 06 03 55 04 03 13 2b 53 74 61 72 66 69 65 6c 64 20



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   53 65 63 75 72 65 20 43 65 72 74 69 66 69 63 61 74 65 20 41 75 74 68
   6f 72 69 74 79 20 2d 20 47 32 30 1e 17 0d 32 30 31 30 30 31 31 39 33
   38 33 36 5a 17 0d 32 31 31 31 30 32 31 39 33 38 33 36 5a 30 3e 31 21
   30 1f 06 03 55 04 0b 13 18 44 6f 6d 61 69 6e 20 43 6f 6e 74 72 6f 6c
   20 56 61 6c 69 64 61 74 65 64 31 19 30 17 06 03 55 04 03 0c 10 2a 2e
   74 6f 6f 6c 73 2e 69 65 74 66 2e 6f 72 67 30 82 01 22 30 0d 06 09 2a
   86 48 86 f7 0d 01 01 01 05 00 03 82 01 0f 00 30 82 01 0a 02 82 01 01
   00 b1 e1 37 e8 eb 82 d6 89 fa db f5 c2 4b 77 f0 2c 4a de 72 6e 3e 13
   60 d1 a8 66 1e c4 ad 3d 32 60 e5 f0 99 b5 f4 7a 7a 48 55 21 ee 0e 39
   12 f9 ce 0d ca f5 69 61 c7 04 ed 6e 0f 1d 3b 1e 50 88 79 3a 0e 31 41
   16 f1 b1 02 64 68 a5 cd f5 4a 0a ca 99 96 35 08 c3 7e 27 5d d0 a9 cf
   f3 e7 28 af 37 d8 b6 7b dd f3 7e ae 6e 97 7f f7 ca 69 4e cc d0 06 df
   5d 27 9b 3b 12 e7 e6 fe 08 6b 52 7b 82 11 7c 72 b3 46 eb c1 e8 78 b8
   0f cb e1 eb bd 06 44 58 dc 83 50 b2 a0 62 5b dc 81 b8 36 e3 9e 7c 79
   b2 a9 53 8a e0 0b c9 4a 2a 13 39 31 13 bd 2c cf a8 70 cf 8c 8d 3d 01
   a3 88 ae 12 00 36 1d 1e 24 2b dd 79 d8 53 01 26 ed 28 4f c9 86 94 83
   4e c8 e1 14 2e 85 b3 af d4 6e dd 69 46 af 41 25 0e 7a ad 8b f2 92 ca
   79 d9 7b 32 4f f7 77 e8 f9 b4 4f 23 5c d4 5c 03 ae d8 ab 3a ca 13 5f
   5d 5d 5d a1 02 03 01 00 01 a3 82 02 e1 30 82 02 dd 30 0c 06 03 55 1d
   13 01 01 ff 04 02 30 00 30 1d 06 03 55 1d 25 04 16 30 14 06 08 2b 06
   01 05 05 07 03 01 06 08 2b 06 01 05 05 07 03 02 30 0e 06 03 55 1d 0f
   01 01 ff 04 04 03 02 05 a0 30 3d 06 03 55 1d 1f 04 36 30 34 30 32 a0
   30 a0 2e 86 2c 68 74 74 70 3a 2f 2f 63 72 6c 2e 73 74 61 72 66 69 65
   6c 64 74 65 63 68 2e 63 6f 6d 2f 73 66 69 67 32 73 31 2d 32 34 32 2e
   63 72 6c 30 63 06 03 55 1d 20 04 5c 30 5a 30 4e 06 0b 60 86 48 01 86
   fd 6e 01 07 17 01 30 3f 30 3d 06 08 2b 06 01 05 05 07 02 01 16 31 68
   74 74 70 3a 2f 2f 63 65 72 74 69 66 69 63 61 74 65 73 2e 73 74 61 72
   66 69 65 6c 64 74 65 63 68 2e 63 6f 6d 2f 72 65 70 6f 73 69 74 6f 72
   79 2f 30 08 06 06 67 81 0c 01 02 01 30 81 82 06 08 2b 06 01 05 05 07
   01 01 04 76 30 74 30 2a 06 08 2b 06 01 05 05 07 30 01 86 1e 68 74 74
   70 3a 2f 2f 6f 63 73 70 2e 73 74 61 72 66 69 65 6c 64 74 65 63 68 2e
   63 6f 6d 2f 30 46 06 08 2b 06 01 05 05 07 30 02 86 3a 68 74 74 70 3a
   2f 2f 63 65 72 74 69 66 69 63 61 74 65 73 2e 73 74 61 72 66 69 65 6c
   64 74 65 63 68 2e 63 6f 6d 2f 72 65 70 6f 73 69 74 6f 72 79 2f 73 66
   69 67 32 2e 63 72 74 30 1f 06 03 55 1d 23 04 18 30 16 80 14 25 45 81
   68 50 26 38 3d 3b 2d 2c be cd 6a d9 b6 3d b3 66 63 30 2b 06 03 55 1d
   11 04 24 30 22 82 10 2a 2e 74 6f 6f 6c 73 2e 69 65 74 66 2e 6f 72 67
   82 0e 74 6f 6f 6c 73 2e 69 65 74 66 2e 6f 72 67 30 1d 06 03 55 1d 0e
   04 16 04 14 ad 8a b4 1c 07 51 d7 92 89 07 b0 b7 84 62 2f 36 55 7a 5f
   4d 30 82 01 06 06 0a 2b 06 01 04 01 d6 79 02 04 02 04 81 f7 04 81 f4
   00 f2 00 77 00 f6 5c 94 2f d1 77 30 22 14 54 18 08 30 94 56 8e e3 4d
   13 19 33 bf df 0c 2f 20 0b cc 4e f1 64 e3 00 00 01 74 e5 ac 71 13 00
   00 04 03 00 48 30 46 02 21 00 8c f5 48 52 ce 56 35 43 39 11 cf 10 cd
   b9 1f 52 b3 36 39 22 3a d1 38 a4 1d ec a6 fe de 1f e9 0f 02 21 00 bc
   a2 25 43 66 c1 9a 26 91 c4 7a 00 b5 b6 53 ab bd 44 c2 f8 ba ae f4 d2
   da f2 52 7c e6 45 49 95 00 77 00 5c dc 43 92 fe e6 ab 45 44 b1 5e 9a
   d4 56 e6 10 37 fb d5 fa 47 dc a1 73 94 b2 5e e6 f6 c7 0e ca 00 00 01
   74 e5 ac 72 3c 00 00 04 03 00 48 30 46 02 21 00 a5 e0 90 6e 63 e9 1d



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   4f dd ef ff 03 52 b9 1e 50 89 60 07 56 4b 44 8a 38 28 f5 96 dc 6b 28
   72 6d 02 21 00 fc 91 ea ed 02 16 88 66 05 4e e1 8a 2e 53 46 c4 cc 51
   fe b3 fa 10 a9 1d 2e db f9 91 25 f8 6c e6 30 0d 06 09 2a 86 48 86 f7
   0d 01 01 0b 05 00 03 82 01 01 00 14 04 3f a0 be d2 ee 3f a8 6e 3a 1f
   78 8e a0 4c 35 53 0f 11 06 1f ff 60 a1 6d 0b 83 e9 d9 2a db b3 3f 9d
   b3 d7 e0 59 4c 19 a8 e4 19 a5 0c a7 70 72 77 63 d5 fe 64 51 0a d2 7a
   d6 50 a5 8a 92 38 ec cb 2f 0f 5a c0 64 58 4d 5c 06 b9 73 63 68 27 8b
   89 34 dc 79 c7 1d 3a fd 34 5f 83 14 41 58 49 80 68 29 80 39 8a 86 72
   69 cc 79 37 ce e3 97 f7 dc f3 95 88 ed 81 03 29 00 d2 a2 c7 ba ab d6
   3a 8e ca 09 0b d9 fb 39 26 4b ff 03 d8 8e 2d 3f 6b 21 ca 8a 7d d8 5f
   fb 94 ba 83 de 9c fc 15 8d 61 fa 67 2d b0 c7 db 3d 25 0a 41 4a 85 d3
   7f 49 46 37 3c f4 b1 75 d0 52 f3 dd c7 66 f1 4b fd aa 00 ed bf e4 7e
   ed 01 ec 7b e4 f6 46 fc 31 fd 72 fe 03 d2 f2 65 af 4d 7e e2 81 9b 7a
   fd 30 3c f5 52 f4 05 34 a0 8a 3e 19 41 58 c8 a8 e0 51 71 84 09 15 ae
   ec a5 77 75 fa 18 f7 d5 77 d5 31 cc c7 2d

A.4.1.  Example: C509 Certificate Encoding

   The CBOR encoding (~C509Certificate) of the first X.509 certificate
   is shown below in CBOR diagnostic format.

/This defines a CBOR Sequence (RFC 8742):/

3,
h'A6A55C870E39B40E',
23,
[
 -4, "US",
 -6, "Arizona",
 -5, "Scottsdale",
 -8, "Starfield Technologies, Inc.",
 -9, "http://certs.starfieldtech.com/repository/",
 -1, "Starfield Secure Certificate Authority - G2"
],
1601581116,
1635881916,
[
  -9, "Domain Control Validated",
   1, "*.tools.ietf.org"
],
0,
h'B1E137E8EB82D689FADBF5C24B77F02C4ADE726E3E1360D1A8661EC4AD3D3260
  E5F099B5F47A7A485521EE0E3912F9CE0DCAF56961C704ED6E0F1D3B1E508879
  3A0E314116F1B1026468A5CDF54A0ACA99963508C37E275DD0A9CFF3E728AF37
  D8B67BDDF37EAE6E977FF7CA694ECCD006DF5D279B3B12E7E6FE086B527B8211
  7C72B346EBC1E878B80FCBE1EBBD064458DC8350B2A0625BDC81B836E39E7C79
  B2A9538AE00BC94A2A13393113BD2CCFA870CF8C8D3D01A388AE1200361D1E24
  2BDD79D8530126ED284FC98694834EC8E1142E85B3AFD46EDD6946AF41250E7A



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  AD8BF292CA79D97B324FF777E8F9B44F235CD45C03AED8AB3ACA135F5D5D5DA1',
[
-4, -2,
 8, [ 1, 2 ],
 -2, 5,
 5, ["http://crl.starfieldtech.com/sfig2s1-242.crl"],
 6, [ h'6086480186fd6e01071701',
      [1, "http://certificates.starfieldtech.com/repository/"], 1 ],
 9, [ 1, "http://ocsp.starfieldtech.com/",
      2, "http://certificates.starfieldtech.com/repository/sfig2.crt" ],
 7, h'254581685026383D3B2D2CBECD6AD9B63DB36663',
 3, [ 2, "*.tools.ietf.org", 2, "tools.ietf.org" ],
 1, h'AD8AB41C0751D7928907B0B784622F36557A5F4D',
10, [
    h'F65C942FD1773022145418083094568EE34D131933BFDF0C2F200BCC4EF164E3',
    1715,
    0,
    h'8CF54852CE5635433911CF10CDB91F52B33639223AD138A41DECA6FEDE1FE90F
      BCA2254366C19A2691C47A00B5B653ABBD44C2F8BAAEF4D2DAF2527CE6454995',
    h'5CDC4392FEE6AB4544B15E9AD456E61037FBD5FA47DCA17394B25EE6F6C70ECA',
    2012,
    0,
    h'A5E0906E63E91D4FDDEFFF0352B91E50896007564B448A3828F596DC6B28726D
      FC91EAED02168866054EE18A2E5346C4CC51FEB3FA10A91D2EDBF99125F86CE6'
    ]
],
h'14043FA0BED2EE3FA86E3A1F788EA04C35530F11061FFF60A16D0B83E9D92ADB
  B33F9DB3D7E0594C19A8E419A50CA770727763D5FE64510AD27AD650A58A9238
  ECCB2F0F5AC064584D5C06B9736368278B8934DC79C71D3AFD345F8314415849
  80682980398A867269CC7937CEE397F7DCF39588ED81032900D2A2C7BAABD63A
  8ECA090BD9FB39264BFF03D88E2D3F6B21CA8A7DD85FFB94BA83DE9CFC158D61
  FA672DB0C7DB3D250A414A85D37F4946373CF4B175D052F3DDC766F14BFDAA00
  EDBFE47EED01EC7BE4F646FC31FD72FE03D2F265AF4D7EE2819B7AFD303CF552
  F40534A08A3E194158C8A8E05171840915AEECA57775FA18F7D577D531CCC72D'

   The size of the CBOR encoding (CBOR sequence) is 1245 bytes.

Acknowledgments

   The authors want to thank Henk Birkholz, Carsten Bormann, Russ
   Housley, Olle Johansson, Benjamin Kaduk, Ilari Liusvaara, Laurence
   Lundblade, Francesca Palombini, Thomas Peterson, Michael Richardson,
   Stefan Santesson, Jim Schaad, Brian Sipos, Fraser Tweedale, and Rene
   Struik for reviewing and commenting on intermediate versions of the
   draft and help with GitHub.






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Contributors

   Special acknowledgement goes to Lijun Liao for his careful review and
   many detailed improvement proposals.

Authors' Addresses

   John Preuß Mattsson
   Ericsson AB
   Email: john.mattsson@ericsson.com


   Göran Selander
   Ericsson AB
   Email: goran.selander@ericsson.com


   Shahid Raza
   RISE AB
   Email: shahid.raza@ri.se


   Joel Höglund
   RISE AB
   Email: joel.hoglund@ri.se


   Martin Furuhed
   Nexus Group
   Email: martin.furuhed@nexusgroup.com





















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