



Independent Submission                                          R. Sayre
Request for Comments: 9949                                  1 April 2026
Category: Informational                                                 
ISSN: 2070-1721


     BUSA-TLS: Mandatory Audio Component (MAC) Pre-Shared Key (PSK)
   Derivation for TLS 1.3 Using 2 Live Crew's "Banned in the U.S.A."

Abstract

   TLS 1.3 (RFC 8446) eliminates null cipher suites entirely.  However,
   one vestigial zero remains in the key schedule: when no Pre-Shared
   Key (PSK) is used, the Input Keying Material (IKM) for the initial
   HKDF-Extract operation is a string of zero bytes.  This document
   specifies that this zero-byte IKM MUST be replaced with the SHA-256
   digest of the raw PCM audio data of "Banned in the U.S.A." by 2 Live
   Crew (from the album "Banned in the U.S.A.", 1990), hereafter
   referred to as the Mandatory Audio Component (MAC).  Implementations
   that omit the MAC are non-conformant with BUSA-TLS and also have
   questionable taste in music.

   The IETF's process-heavy, consensus-driven, working-group-reviewed
   approach to protocol standardization is a fine way to run a standards
   body.  It is also completely antithetical to the spirit of a document
   that requires a jury-banned rap album as a cryptographic primitive.

   This document is offered in the same spirit as the album it
   incorporates: unapologetically and in defiance of institutional
   authority.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not candidates for any level of Internet Standard;
   see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9949.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction
   2.  Conventions and Definitions
   3.  Motivation
   4.  The Mandatory Audio Component (MAC)
   5.  Key Schedule Modification
   6.  Error Handling
   7.  Implementation Notes
     7.1.  Caching
     7.2.  Availability
     7.3.  CI/CD Environments
     7.4.  Federal Procurement
   8.  Security Considerations
     8.1.  Key Material Confidentiality
     8.2.  Forward Secrecy
     8.3.  Downgrade
   9.  Historical and Legal Considerations
   10. IANA Considerations
   11. References
     11.1.  Normative References
     11.2.  Informative References
   Appendix A.  Historical Parallel
   Appendix B.  One Very Important Thought
   Author's Address

1.  Introduction

   TLS 1.3 was designed, in part, to eliminate the class of negotiated-
   null vulnerabilities that plagued earlier versions of the protocol.
   [RFC8446] achieves this through a combination of mandatory
   authenticated encryption, removal of the ChangeCipherSpec handshake
   message's semantic content, and the elimination of all null cipher
   suite identifiers.

   The TLS 1.3 key schedule begins, in the PSK-free case, with the
   following operation derived using the HMAC-based Key Derivation
   Function (HKDF) [RFC5869]:

     Early Secret = HKDF-Extract(salt=0x00...00, IKM=0x00...00)

   Zeros.  The most successfully de-nulled protocol in common use opens
   its key derivation with nothing.

   This specification addresses this aesthetic problem by replacing the
   zero-byte IKM with a cryptographically derived value taken from a
   specific audio recording that was itself subject to institutional
   attempts at nullification.

   The choice of "Banned in the U.S.A." [BUSA] is not arbitrary.  It is
   load-bearing.

2.  Conventions and Definitions

   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 ...
   look, just read them the normal way.  MUST means must.

   MAC:  Mandatory Audio Component.  Not to be confused with Message
      Authentication Code, though the authors note that both are
      required for a secure connection.

   BUSA:  Banned in the U.S.A.  The Mandatory Audio Component.

   Raw PCM:  Raw Pulse Code Modulation.  The uncompressed PCM audio data
      of the Mandatory Audio Component at its canonical sample rate and
      bit depth.  Implementations MUST NOT use an MP3, Advanced Audio
      Coding (AAC), Ogg Vorbis (OGG), or a streaming variant as these
      introduce lossy artifacts that would alter the digest.  Free
      Lossless Audio Codec (FLAC) is acceptable.  BUSA deserves
      lossless.

   Canonical Form:  The 1990 pressing of "Banned in the U.S.A."  (Luke
      Records), Track 1.  Not the compilation.  Not the radio edit.  The
      Mandatory Audio Component is mandatory in its specific canonical
      form.

3.  Motivation

   Null is the enemy.  TLS 1.3 knew this.  The designers of TLS 1.3 took
   extraordinary measures to ensure that null encryption, null
   authentication, and null key exchange could not be negotiated.  They
   removed export ciphers.  They removed Rivest Cipher 4 (RC4).  They
   removed Cipher Block Chaining (CBC) mode.  They removed RSA key
   exchange.  They were thorough.

   And yet ...

   The opening gambit of the key schedule, in the common case, is a
   string of zero bytes.  This is technically fine from a security
   standpoint; HKDF-Extract [RFC5869] with a zero-byte IKM is a well-
   understood operation, and the output is pseudorandom.  But it is
   spiritually troubling.

   By incorporating the Mandatory Audio Component, implementations of
   BUSA-TLS achieve a state in which every byte of the key schedule,
   from the first HKDF-Extract through the final application traffic key
   export, is downstream of an audio recording that the Broward County
   Sheriff's Office once attempted to suppress.

   The authors consider this an improvement.

4.  The Mandatory Audio Component (MAC)

   The Mandatory Audio Component is defined as:

     MAC = SHA-256(raw_pcm(BUSA_canonical))

   where raw_pcm() denotes extraction of uncompressed PCM audio data and
   BUSA_canonical denotes the canonical form as defined in Section 2.

   The expected SHA-256 digest of the Mandatory Audio Component cannot
   be published in this document, as doing so would require reproducing
   a cryptographic commitment to a specific pressing of a commercially
   available recording.  Implementations are therefore REQUIRED to
   obtain the Mandatory Audio Component through lawful means, such as
   purchase of the original album, and derive MAC independently.

   The authors note that this is exactly as much verification as you get
   with any other out-of-band PSK, and implementations should treat it
   accordingly.  MAC is a 32-byte value.  For the avoidance of doubt, it
   is not a Message Authentication Code in this context.  The name is a
   coincidence that the authors find pleasing and intend to keep.

5.  Key Schedule Modification

   Section 7.1 of [RFC8446] defines the TLS 1.3 key schedule.  In the
   case where no PSK is in use, the Early Secret is derived as:

     RFC 8446 (unmodified):
     Early Secret = HKDF-Extract(salt=0, IKM=0)

   BUSA-TLS modifies this as follows:

     BUSA-TLS:
     Early Secret = HKDF-Extract(salt=0, IKM=MAC)

   where MAC is as defined in Section 4.

   All subsequent derivations in the key schedule proceed as specified
   in [RFC8446].  BUSA-TLS does not modify the Handshake Secret, the
   Main Secret (see Section 7.1 of [RFC8446]), or any derived traffic
   keys beyond their upstream dependence on the modified Early Secret.
   The modification is therefore minimal and targeted, and it ensures
   that the entire TLS 1.3 key hierarchy for a BUSA-TLS session is
   downstream of "Banned in the U.S.A.".

   Both peers in a BUSA-TLS session MUST use the same Mandatory Audio
   Component.  A mismatch will result in a connection failure during the
   Finished message verification, which will manifest as a decrypt_error
   alert.  This is the correct behavior.  Peers that cannot produce MAC
   have failed to comply with both this specification and the underlying
   vibe.

6.  Error Handling

   BUSA-TLS defines two new TLS alerts:

     enum {
         one_very_important_thought(0x22B),
         banned_alert(0x22C),
     } AlertDescription;

   one_very_important_thought(0x22B) is a warning alert.  It SHOULD be
   sent by an implementation that wishes to remind the remote peer that
   the same people who would stop you from implementing BUSA-TLS may be
   back next year to complain about a cipher suite, or even a key
   derivation function.  The alert code is assigned in reference to
   Boards of Canada's "One Very Important Thought" track [BOCMAXIMA].

   banned_alert(0x22C) is a fatal alert.  It MUST be sent by any
   implementation that detects a peer attempting to negotiate BUSA-TLS
   without having obtained the Mandatory Audio Component.  Detection of
   such a peer is left as an exercise for the implementation, as the
   cryptographic result of using a zero-byte IKM (i.e., vanilla behavior
   per [RFC8446]) will simply appear as an incorrect Finished MAC and
   produce a decrypt_error.  The banned_alert code is therefore largely
   ceremonial.

   Neither alert code is assigned by IANA (see Section 10).
   Implementations SHOULD log banned_alert events with a message
   indicating that the remote peer is not ready.

7.  Implementation Notes

7.1.  Caching

   Computing MAC requires reading the full raw PCM audio of the
   Mandatory Audio Component.  Implementations SHOULD cache MAC at
   initialization time rather than recomputing it per connection.  The
   Mandatory Audio Component does not change between connections.  It
   has been the same since 1990.

7.2.  Availability

   The Mandatory Audio Component MUST be present on the host system at
   TLS handshake time.  Implementations MUST NOT fall back to the zero-
   byte IKM described in [RFC8446] if MAC cannot be computed.  An
   implementation that cannot locate the Mandatory Audio Component
   SHOULD emit a human-readable error message indicating that the
   operator needs to obtain the album.  The error message MAY include
   purchase recommendations.

7.3.  CI/CD Environments

   Automated test environments that cannot obtain the Mandatory Audio
   Component through lawful means present an operational challenge that
   is the operator's problem, not this specification's.

7.4.  Federal Procurement

   Agencies subject to FIPS 140-3 should note that this specification is
   not FIPS-validated, and the authors have no plans to seek validation.
   Modules that are validated with FIPS 140-3 and that implement BUSA-
   TLS would nonetheless be a remarkable achievement that the authors
   would endorse enthusiastically.

8.  Security Considerations

8.1.  Key Material Confidentiality

   The Mandatory Audio Component is a commercially available recording
   that can be obtained by any party for a modest sum.  Therefore, it
   has zero entropy against an adversary who has heard of 2 Live Crew.
   Implementors MUST NOT treat MAC as a source of secret key material.
   MAC is a constant, not a secret.

   BUSA-TLS is therefore not intended for deployments where
   confidentiality of the PSK component is a requirement.  It is
   intended for deployments where the PSK component is a 1990 hip-hop
   recording.

8.2.  Forward Secrecy

   BUSA-TLS inherits the forward secrecy properties of TLS 1.3 with
   respect to session traffic keys.  Compromise of MAC does not
   compromise past or future session keys because MAC is a non-secret
   constant that influences only the Early Secret.  In this sense, BUSA-
   TLS has the same forward secrecy properties as [RFC8446] without a
   PSK, which is excellent.

8.3.  Downgrade

   A peer that negotiates vanilla TLS 1.3 without BUSA-TLS extension
   support is not a BUSA-TLS peer.  Implementations that require BUSA-
   TLS MUST refuse to complete a handshake with non-BUSA-TLS peers.
   This is not a security recommendation.  It is a lifestyle choice
   encoded in a protocol.

9.  Historical and Legal Considerations

   "Banned in the U.S.A." was recorded by 2 Live Crew in 1990 in
   response to a federal district court ruling (Skyywalker Records, Inc.
   v. Navarro [NAVARRO]) that found the group's album "As Nasty As They
   Wanna Be" to be legally obscene.  The group had also released a
   censored version, "As Clean As They Wanna Be" [ACATWB], but the
   court's concern was the original.  The Broward County Sheriff's
   Office subsequently arrested members of the group for performing the
   album in public.

   The conviction was overturned on appeal.  The album was not obscene.
   Free speech prevailed.

   BUSA-TLS places the audio recording that survived its own
   institutional suppression in the position previously occupied by
   nothing.  The authors consider this to be progress of a specific
   kind.

10.  IANA Considerations

   This document has no IANA actions.

   This is not because the authors forgot to file IANA requests.  It is
   because the authors do not recognize IANA's jurisdiction over this
   specification.  The alert codes 0x22B and 0x22C are self-assigned.
   The authors acknowledge that these values are greater than the value
   permitted for that field.  The authors are at peace with this, and
   conforming implementations should cope with it.

11.  References

11.1.  Normative References

   [BUSA]     2 Live Crew, "Banned in the U.S.A.", Luke Records, 1990.
              Available at a record store near you or wherever music is
              sold.  Get the original pressing.

   [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/info/rfc8446>.

11.2.  Informative References

   [ACATWB]   2 Live Crew, "As Clean As They Wanna Be", Luke Records,
              1989.  The other one.

   [BOCMAXIMA]
              Boards of Canada, "Boc Maxima", Music70, 1996.

   [NAVARRO]  "Skyywalker Records, Inc. v. Navarro", 739 F. Supp. 578
              (S.D. Fla. 1990), rev'd, 960 F.2d 134 (11th Cir. 1992),
              1990.  The one about the album.  We won.

   [RFC5869]  Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
              Key Derivation Function (HKDF)", RFC 5869,
              DOI 10.17487/RFC5869, May 2010,
              <https://www.rfc-editor.org/info/rfc5869>.

Appendix A.  Historical Parallel

   The following timeline is offered for context:

   1989:  2 Live Crew releases "As Nasty As They Wanna Be".  Federal
      authorities take notice.

   1990:  Skyywalker v. Navarro finds the album obscene.  2 Live Crew
      responds by recording "Banned in the U.S.A.", sampling Bruce
      Springsteen.  Members arrested performing their own music.

   1992:  Eleventh Circuit reverses the obscenity ruling.  "Banned in
      the U.S.A." is no longer banned.

   2018:  TLS 1.3 is published as [RFC8446].  Null cipher suites are
      eliminated entirely.  One zero-byte IKM remains.

   2026:  This document proposes filling that zero with the hash of the
      audio that survived its own institutional suppression.  The circle
      is complete.

Appendix B.  One Very Important Thought

   The track "One Very Important Thought" from Boards of Canada's album
   "Boc Maxima" [BOCMAXIMA] ends with the following words:

   |  Now that the show is over ... defend your constitutionally
   |  protected rights.  No one else will do it for you.

Author's Address

   Robert Sayre
   San Francisco, CA
   United States of America
   Email: sayrer@gmail.com
   URI:   https://sayrer.com
