Internet Engineering Task Force (IETF)                         S. Turner
Request for Comments: 5756                                          IECA
Updates: 4055                                                   D. Brown
Category: Standards Track                                       Certicom
ISSN: 2070-1721                                                   K. Yiu
                                                              Microsoft
                                                             R. Housley
                                                         Vigil Security
                                                                T. Polk
                                                                   NIST
                                                           January 2010


      Updates for RSAES-OAEP and RSASSA-PSS Algorithm Parameters

Abstract

  This document updates RFC 4055.  It updates the conventions for using
  the RSA Encryption Scheme - Optimal Asymmetric Encryption Padding
  (RSAES-OAEP) key transport algorithm in the Internet X.509 Public Key
  Infrastructure (PKI).  Specifically, it updates the conventions for
  algorithm parameters in an X.509 certificate's subjectPublicKeyInfo
  field.

Status of This Memo

  This is an Internet Standards Track document.

  This document is a product of the Internet Engineering Task Force
  (IETF).  It represents the consensus of the IETF community.  It has
  received public review and has been approved for publication by the
  Internet Engineering Steering Group (IESG).  Further information on
  Internet Standards is available in Section 2 of RFC 5741.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  http://www.rfc-editor.org/info/rfc5756.

Copyright Notice

  Copyright (c) 2010 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
  (http://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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  to this document.  Code Components extracted from this document must
  include Simplified BSD License text as described in Section 4.e of
  the Trust Legal Provisions and are provided without warranty as
  described in the Simplified BSD License.

  This document may contain material from IETF Documents or IETF
  Contributions published or made publicly available before November
  10, 2008.  The person(s) controlling the copyright in some of this
  material may not have granted the IETF Trust the right to allow
  modifications of such material outside the IETF Standards Process.
  Without obtaining an adequate license from the person(s) controlling
  the copyright in such materials, this document may not be modified
  outside the IETF Standards Process, and derivative works of it may
  not be created outside the IETF Standards Process, except to format
  it for publication as an RFC or to translate it into languages other
  than English.

1.  Introduction

  RFC 4055 specifies conventions for using the RSA Encryption Scheme -
  Optimal Asymmetric Encryption Padding (RSAES-OAEP) key transport
  algorithm in the Internet X.509 Public Key Infrastructure (PKI).  It
  provides algorithm identifiers and parameters for RSAES-OAEP.

  This document updates the conventions for RSAES-OAEP parameters in
  the subjectPublicKeyInfo field of an X.509 certificate.  The PKIX WG
  Elliptic Curve Cryptography (ECC) design team recommended that Key
  Derivation Functions (KDFs) should not be constrained within a
  certificate; rather, KDF constraints should be negotiated in
  protocols that need to employ certificates.

  Only two paragraphs in [RFC4055] discuss RSAES-OAEP parameters in
  X.509 certificates: the second paragraph of Section 4 and the first
  paragraph of Section 4.1.  This document only updates these two
  paragraphs.  Section 3 updates the second paragraph in Section 4 of
  [RFC4055], while Section 4 updates the second paragraph in Section
  4.1 of [RFC4055].  "Old:" prefaces the text to be replaced and "New:"
  prefaces the replacement text.

  This document also replaces incorrect references to the
  publicKeyAlgorithms field in Section 3 with references to the
  parameters field in the subjectPublicKeyInfo algorithm field.
  Section 3 also rewords the second and third paragraphs for clarity.








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1.1.  Conventions Used in This Document

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
  document are to be interpreted as described in [RFC2119].

2.  Changes to Section 3 (Second and Third Paragraphs)

  This change clarifies the placement of RSASSA-PSS-params in the
  signature, signatureAlgorithm, and subjectPublicKeyInfo fields for
  certification authority (CA) and end-entity (EE) certificates.  It
  also clarifies the placement of RSASSA-PSS-params in the
  signatureAlgorithm field in certificate revocation lists (CRLs).

  Old:

  CAs that issue certificates with the id-RSASSA-PSS algorithm
  identifier SHOULD require the presence of parameters in the
  publicKeyAlgorithms field if the cA boolean flag is set in the basic
  constraints certificate extension.  CAs MAY require that the
  parameters be present in the publicKeyAlgorithms field for end-entity
  certificates.

  CAs that use the RSASSA-PSS algorithm for signing certificates SHOULD
  include RSASSA-PSS-params in the subjectPublicKeyInfo algorithm
  parameters in their own certificates.  CAs that use the RSASSA-PSS
  algorithm for signing certificates or CRLs MUST include RSASSA-PSS-
  params in the signatureAlgorithm parameters in the TBSCertificate or
  TBSCertList structures.

  New:

  When the id-RSASSA-PSS object identifier appears in the
  TBSCertificate or TBSCertList signature algorithm field, then the
  RSASSA-PSS-params structure MUST be included in the TBSCertificate or
  TBSCertList signature parameters field.

  When the id-RSASSA-PSS object identifier appears in the
  TBSCertificate subjectPublicKeyInfo algorithm field of CA
  certificates, then the parameters field SHOULD include the RSASSA-
  PSS-params structure.  When the id-RSASSA-PSS object identifier
  appears in the TBSCertificate subjectPublicKeyInfo algorithm field of
  EE certificates, then the parameters field MAY include the RSASSA-
  PSS-params structure.







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  All certificates and CRLs signed by a CA that supports the id-RSASSA-
  PSS algorithm MUST include the RSASSA-PSS-params in the
  signatureAlgorithm parameters in Certificate and CertList structures,
  respectively.

3.  Changes to Section 4 (Second Paragraph)

  This change prohibits the inclusion of RSAES-OAEP-params in the
  subjectPublicKeyInfo field.  This was done because a) it does not
  affect interoperability and b) it aligns with PKIX practice to not
  include limitations on how the public key can be used in
  subjectPublicKeyInfo.  A poll of implementers was taken and there
  were no objections to this change as it did not affect current
  implementations.

  Old:

  CAs that issue certificates with the id-RSAES-OAEP algorithm
  identifier SHOULD require the presence of parameters in the
  publicKeyAlgorithms field for all certificates.  Entities that use a
  certificate with a publicKeyAlgorithm value of id-RSA-OAEP where the
  parameters are absent SHOULD use the default set of parameters for
  RSAES-OAEP-params.  Entities that use a certificate with a
  publicKeyAlgorithm value of rsaEncryption SHOULD use the default set
  of parameters for RSAES-OAEP-params.

  New:

  CAs that issue certificates with the id-RSAES-OAEP algorithm
  identifier MUST NOT include parameters in the subjectPublicKeyInfo
  algorithm field.

4.  Changes to Section 4.1 (First Paragraph)

  This change prohibits the inclusion of parameters in the
  subjectPublicKeyInfo field.  This was done because a) it does not
  affect interoperability and b) it aligns with PKIX practice to not
  include limitations on how the public key can be used in
  subjectPublicKeyInfo.  A poll of implementers was taken and there
  were no objections to this change as it did not affect current
  implementations.

  Old:

  When id-RSAES-OAEP is used in an AlgorithmIdentifier, the parameters
  MUST employ the RSAES-OAEP-params syntax.  The parameters may be
  either absent or present when used as subject public key information.




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  The parameters MUST be present when used in the algorithm identifier
  associated with an encrypted value.

  New:

  When id-RSAES-OAEP is used in an AlgorithmIdentifier, the parameters
  MUST employ the RSAES-OAEP-params syntax.  The parameters MUST be
  absent when used in the subjectPublicKeyInfo field.  The parameters
  MUST be present when used in the algorithm identifier associated with
  an encrypted value.

5.  Security Considerations

  The security considerations from [RFC4055] apply.

  If the RSAES-OAEP-params are negotiated, then the negotiation
  mechanism needs to provide integrity for these parameters.  For
  example, an S/MIME Agent can advertise their capabilities in the
  SMIMECapabilities attribute, which is either a signed attribute
  [RFC5751] or a certificate extension [RFC4262].

6.  References

6.1.  Normative References

  [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.

  [RFC4055]     Schaad, J., Kaliski, B., and R. Housley, "Additional
                Algorithms and Identifiers for RSA Cryptography for use
                in the Internet X.509 Public Key Infrastructure
                Certificate and Certificate Revocation List (CRL)
                Profile", RFC 4055, June 2005.

6.2.  Informative References

  [RFC4262]     Santesson, S., "X.509 Certificate Extension for
                Secure/Multipurpose Internet Mail Extensions (S/MIME)
                Capabilities", RFC 4262, December 2005.

  [RFC5751]     Ramsdell, B. and S. Turner, "Secure/Multipurpose
                Internet Mail Extensions (S/MIME) Version 3.2 Message
                Specification", RFC 5751, January 2010.








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Authors' Addresses

  Sean Turner
  IECA, Inc.
  3057 Nutley Street, Suite 106
  Fairfax, VA 22031
  USA

  EMail: [email protected]


  Kelvin Yiu
  Microsoft
  One Microsoft Way
  Redmond, WA 98052-6399
  USA

  EMail: [email protected]


  Daniel R. L. Brown
  Certicom Corp
  5520 Explorer Drive #400
  Mississauga, ON L4W 5L1
  CANADA

  EMail: [email protected]


  Russ Housley
  Vigil Security, LLC
  918 Spring Knoll Drive
  Herndon, VA 20170
  USA

  EMail: [email protected]


  Tim Polk
  NIST
  Building 820, Room 426
  Gaithersburg, MD 20899
  USA

  EMail: [email protected]






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