



Network Working Group                                         V. Smyslov
Internet-Draft                                                ELVIS-PLUS
Intended status: Experimental                            16 October 2025
Expires: 19 April 2026


 Using the Internet Key Exchange Protocol Version 2 (IKEv2) for PSP Key
                               Management
                   draft-smyslov-ipsecme-ikev2-psp-00

Abstract

   This document specifies how the Internet Key Exchange Version 2
   (IKEv2) protocol can be used for supplying keys for the PSP Security
   Protocol (PSP).

Status of This Memo

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

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   This Internet-Draft will expire on 19 April 2026.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Notation  . . . . . . . . . . . . . . . . . .   2
   3.  PSP . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  PSP Key Management Using IKEv2  . . . . . . . . . . . . . . .   3
     4.1.  The IKE_SA_INIT Exchange  . . . . . . . . . . . . . . . .   3
     4.2.  The IKE_AUTH Exchange . . . . . . . . . . . . . . . . . .   4
     4.3.  The Modified CREATE_CHILD_SA Exchange . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Internet Key Exchange Version 2 (IKEv2) protocol [RFC7296] is used in
   IPsec architecture [RFC4301] for the purpose SA negotiation and key
   management.  It provides authenticated key exchange and calculates
   session keys for the Encapsulating Security Payload (ESP) protocol
   [RFC4303].

   PSP Security Protocol (PSP) is defined in [PSP].  The protocol
   utilizes the concept of so called "stateless encryption" by keeping
   only global state for decrypting incoming packets.  This concept
   implies that the receiving side of Security Association (SA) provides
   the sending side with a key at the time this SA is being created.

   PSP is considered as an alternative for ESP for high-speed
   communications (e.g., inside data centers).  However, IKEv2 cannot
   directly be used for providing keys for PSP, since the way IPsec keys
   are being obtained in IKEv2 implies that they are derived from the
   ephemeral key exchange and thus are unpredictable.  This is
   incompatible with the way keys are used in PSP where each side must
   independently generate keys used for decryption for a particular SA
   based on some global key.

2.  Terminology and Notation

   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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3.  PSP

   PSP [PSP] is a security protocol created by Google for encryption on
   IP level.  PSP was designed to address the high-speed encryption
   requirements of large-scale data centers.  To avoid storing per-SA
   decryption keys on the receiver side, the decryption keys are derived
   from the SPI (that is present in the packet) plus a global secret
   known only to the receiver side.

   PSP specification does not address key management issues.  It assumes
   that at the time an SA is being created the sender asks the receiver
   to create an SA encryption key, which the receiver then somehow
   communicates securely to the sender.

4.  PSP Key Management Using IKEv2

   IKEv2 cannot directly be used for providing keys for PSP, because its
   specification [RFC7296] assumes that keying material for Child SAs is
   derived using initial ephemeral key exchange.  Thus, peers contribute
   to this keying material, but cannot control it and for this reason
   cannot provide each other with arbitrary keys.

   On the other hand, IKEv2 extension for group key management
   [I-D.ietf-ipsecme-g-ikev2] does allow this functionality as it is
   needed for providing members of a group with identical keys.  This
   specification re-uses the ability to download arbitrary keys in IKEv2
   from [I-D.ietf-ipsecme-g-ikev2].  Note that unlike
   [I-D.ietf-ipsecme-g-ikev2] this specification is for unicast (peer-
   to-peer) communication.

   Since both peers have to provide each other with keying material, it
   is not possible to do that in the IKE_AUTH exchange (as in
   [RFC7296]), since the initiator in this case would send its key
   (which is sensitive information) to the not-yet-authenticated
   responder.  For this reason, peers MUST create IKE SA childless as
   specified in [RFC6023].  Once childless IKE SA is created, peers can
   use the modified CREATE_CHILD_SA exchange to create or rekey Child
   SAs utilizing PSP.

4.1.  The IKE_SA_INIT Exchange

   Peers wishing to use IKEv2 for providing keys for PSP MUST negotiate
   the Key Wrap Algorithm (KWA) transform (Section 4.4.2.1.2 of
   [I-D.ietf-ipsecme-g-ikev2]) in the IKE_SA_INIT exchange.  If the
   initiator is not sure that the responder supports PSP and if using
   PSP is optional for the initiator, then the initiator MAY include two
   proposals into the IKE_SA_INIT request - one with the Key Wrap
   Algorithm transform (aiming for responders supporting PSP) and the



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   other without it.

   The responder supporting PSP key management, besides negotiation of
   the KWA transform, MUST also include the CHILDLESS_IKEV2_SUPPORTED
   notification (Section 4 of [RFC6023]) in the IKE_SA_INIT response.

   Even if the KWA transform is negotiated, it does not mean that this
   IKE SA is for creating PSP SAs only - such an SA MAY be used for
   creating both ESP and PSP SAs.

4.2.  The IKE_AUTH Exchange

   The PSP Child SA cannot be created in the IKE_AUTH exchange.  On the
   other hand, peers may create the ESP Child SA in this exchange if
   they want to.  Otherwise, the IKE SA is created childless and the
   IKE_AUTH exchange is as defined in Section 5 of [RFC6023].

4.3.  The Modified CREATE_CHILD_SA Exchange

   Modified CREATE_CHILD_SA exchange is used for creating the PSP SA.
   The following modifications are made.

   *  The SA payload MUST contain one or more Proposal substructures
      with the Protocol ID field set to a new Security Protocol
      Identifier PSP (<TBA by IANA>).  Note that SPI Size for PSP is the
      same as for ESP (4 octets).  Proposals with other Security
      Protocol Identifiers MUST NOT be present.

   *  These Proposal substructures MUST only contain one or more
      Transform substructures with new Transform Type "PSP Parameters
      (PSP)" (<TBA by IANA>).  See Section 6, Paragraph 2, Item 1 for
      Possible Transform IDs for this Transform Type.  Transform
      substructures with other Transform Types MUST NOT be present.

   *  The CREATE_CHILD_SA messages MUST NOT contain the Key Exchange
      (KE) and the Nonce (Ni and Nr) payloads.  Instead, both request
      and response MUST contain exactly one Key Download (KD) payload,
      defined in Section 4.5 of [I-D.ietf-ipsecme-g-ikev2].  The sender
      of a KD payload provides a keying material for the PSP SA that it
      will use as a receiver to its peer.

   *  The KD payloads MUST contain exactly one or more Group Key Bag
      substructure, defined in Section 4.5.2 of
      [I-D.ietf-ipsecme-g-ikev2].  The Protocol field of this
      substructures MUST be set to Security Protocol Identifier PSP
      (<TBA by IANA>), the SPI MUST match that in one of the Proposal
      substructures in the SA payload.




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   *  Each Key Bag MUST contain exactly one SA_KEY attribute, defined in
      Section 4.5.2.1 of [I-D.ietf-ipsecme-g-ikev2], in which the
      wrapped keying material (See Section 4.5.4 of
      [I-D.ietf-ipsecme-g-ikev2]) for the PSP SA is provided.  The Key
      ID and the KWK ID fields MUST be set to zero, meaning that this
      attribute contains the keying material for an SA and this keying
      material is protected with the default Key Wrap Key SK_w that is
      calculated as

      SK_w = prf+(SK_d, "Key Wrap for PSP")

   *  The size of the provided keying material MUST be sufficient to get
      keys for any of the proposed PSP parameters.

   The modified CREATE_CHILD_SA exchange is shown below.

   Initiator                         Responder
   ------------------------------------------------------------------
   HDR, SK {[N(REKEY_SA),]
        SA, KD, TSi, TSr}   --->

                             <---    HDR, SK {SA, KD, TSi, TSr}

                 Figure 1: CREATE_CHILD_SA Exchange for PSP

   The USE_TRANSPORT_MODE notification can be used in case of PSP to
   indicate that the PSP SA is to be created using transport mode, as
   with ESP.

   The REKEY_SA notification can be present and plays the same role as
   with ESP SA - indicates the SA to be replaced with a newly created
   SA.

5.  Security Considerations

   To be added.

6.  IANA Considerations

   This document requests IANA to make the following changes in the
   "Internet Key Exchange Version 2 (IKEv2) Parameters" registry group
   [IKEV2-IANA].

   1.  Create new registry "Transform Type <TBA> - PSP Parameters
       Transform IDs".  The registration policy for this registry is
       Expert Review Policy [RFC8126].  The initial values of the new
       registry are:




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      Value                   PSP Parameters
      ------------------------------------------
      0                       Reserved
      1                       PSP Header Version 0, AES-GCM-128
      2                       PSP Header Version 0, AES-GCM-256
      3                       PSP Header Version 0, AES-GMAC-128
      4                       PSP Header Version 0, AES-GMAC-256
      Unassigned             5-1023
      Private Use         1024-65535

   2.  Add new Transform Type "PSP Parameters (PSP)" in the "Transform
       Type Values" registry.

      Type    Description                         Used In
      ---------------------------------------------------
      <TBA>   PSP Parameters (PSP)                (PSP)

   3.  Add new Security Protocol Identifier in the "IKEv2 Security
       Protocol Identifiers" registry.

      Protocol ID       Protocol
      --------------------------
      <TBA>             PSP

7.  References

7.1.  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/info/rfc2119>.

   [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/info/rfc8174>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <https://www.rfc-editor.org/info/rfc7296>.





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   [RFC6023]  Nir, Y., Tschofenig, H., Deng, H., and R. Singh, "A
              Childless Initiation of the Internet Key Exchange Version
              2 (IKEv2) Security Association (SA)", RFC 6023,
              DOI 10.17487/RFC6023, October 2010,
              <https://www.rfc-editor.org/info/rfc6023>.

   [I-D.ietf-ipsecme-g-ikev2]
              Smyslov, V. and B. Weis, "Group Key Management using
              IKEv2", Work in Progress, Internet-Draft, draft-ietf-
              ipsecme-g-ikev2-23, 31 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ipsecme-
              g-ikev2-23>.

   [PSP]      "PSP Architecture Specification", November 2022,
              <https://github.com/google/psp/blob/main/doc/
              PSP_Arch_Spec.pdf>.

7.2.  Informative References

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [IKEV2-IANA]
              IANA, "Internet Key Exchange Version 2 (IKEv2)
              Parameters", <http://www.iana.org/assignments/ikev2-
              parameters/ikev2-parameters.xhtml>.

Author's Address

   Valery Smyslov
   ELVIS-PLUS
   Russian Federation
   Email: svan@elvis.ru













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