RFC 5756 PROPOSED STANDARD PKI · CRYPTOGRAPHY · CERTIFICATES

Updates for RSAES-OAEP and RSASSA-PSS Algorithm Parameters

A small fix to how RSA-OAEP and RSA-PSS parameters appear in X.509 certificates.

RFC EDITOR

Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk, "Updates for RSAES-OAEP and RSASSA-PSS Algorithm Parameters", RFC 5756, DOI 10.17487/RFC5756, January 2010, <https://www.rfc-editor.org/info/rfc5756>.

BIBTEX

@misc{rfc5756,
  series = {Request for Comments},
  number = 5756,
  howpublished = {RFC 5756},
  publisher = {RFC Editor},
  doi = {10.17487/RFC5756},
  url = {https://www.rfc-editor.org/info/rfc5756},
  author = {S. Turner and D. Brown and K. Yiu and R. Housley and T. Polk},
  title = {{Updates for RSAES-OAEP and RSASSA-PSS Algorithm Parameters}},
  pagetotal = 6,
  year = 2010,
  month = jan,
}

PUBLISHED: January 2010
AUTHORS: S. Turner, D. Brown, K. Yiu, R. Housley, T. Polk
STREAM: IETF
BUILDS ON: RFC 4055 — RSA-PSS/OAEP in X.509
OAEP PARAMS IN SUBJECTPUBLICKEYINFO: MUST be absent
PSS PARAMS IN SIGNATURE FIELD: MUST be included
PSS PARAMS IN CA PUBLIC KEY: SHOULD be included
DOI: 10.17487/RFC5756
ERRATA: Reported errata

LINEAGE · FROM THE RFC INDEXOpen full graph →

'05RFC 4055RSA-PSS/OAEP in X.509 '10RFC 5756Updates for RSAES-OAEP and RSASSA-PSS Algorithm Parameters

RFC text

Contents

Original text · RFC Editor View on rfc-editor.org ↗

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
   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.

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.

   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.

   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.

Authors' Addresses

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

   EMail: turners@ieca.com


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

   EMail: kelviny@microsoft.com


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

   EMail: dbrown@certicom.com


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

   EMail: housley@vigilsec.com


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

   EMail: wpolk@nist.gov

AI ELI5

On this page

PROBLEMRFC 4055 let RSAES-OAEP parameters appear in a certificate's public key field and described RSASSA-PSS parameter placement unclearly, even using the wrong field name.

MECHANISMThis document replaces specific paragraphs of RFC 4055. RSAES-OAEP parameters MUST be absent in subjectPublicKeyInfo, and RSASSA-PSS-params placement is spelled out for certificates and CRLs.

WHY IT MATTERSIt updates RFC 4055 in a narrow way, and the authors say implementers had no objections because current implementations were not affected.

§1What This Update Changes

RFC 4055 describes how to use the RSA Encryption Scheme with Optimal Asymmetric Encryption Padding (RSAES-OAEP) in the Internet X.509 Public Key Infrastructure. This document updates RFC 4055 and only touches two paragraphs about RSAES-OAEP parameters in certificates: the second paragraph of its Section 4 and the first paragraph of its Section 4.1. It also fixes incorrect references to a publicKeyAlgorithms field and rewords the second and third paragraphs of RFC 4055 Section 3 for clarity.

The change is motivated by the PKIX Elliptic Curve Cryptography design team's recommendation that Key Derivation Functions (KDFs) should not be constrained within a certificate. Constraints on KDFs should instead be negotiated in the protocols that use certificates. Each change is shown as an Old: block followed by a New: block.

This note fixes a few sentences in an older rulebook. It shows the old words and then the new words.

§2RSASSA-PSS Parameter Placement

The first change clarifies where RSASSA-PSS-params go in the signature, signatureAlgorithm and subjectPublicKeyInfo fields of certification authority (CA) and end-entity (EE) certificates, and in the signatureAlgorithm field of certificate revocation lists (CRLs). The new text says:

When id-RSASSA-PSS appears in the signature algorithm field of a TBSCertificate or TBSCertList, the RSASSA-PSS-params structure MUST be included in the signature parameters field.
In the subjectPublicKeyInfo algorithm field of CA certificates, the parameters field SHOULD include RSASSA-PSS-params. In EE certificates it MAY.
All certificates and CRLs signed by a CA that supports id-RSASSA-PSS MUST include RSASSA-PSS-params in the signatureAlgorithm parameters.

If a certificate is signed with this method, the signing settings must be written next to the signature. On the key itself they are suggested for certificate authorities and optional for everyone else.

§3No RSAES-OAEP Parameters in Public Keys

The second change prohibits putting RSAES-OAEP-params in the subjectPublicKeyInfo field. CAs that issue certificates with the id-RSAES-OAEP algorithm identifier MUST NOT include parameters in the subjectPublicKeyInfo algorithm field. The old text had a SHOULD requiring parameters, and told entities what defaults to use when they were absent.

The RFC gives two reasons: it does not affect interoperability, and it matches the PKIX practice of not placing limits on how a public key can be used in subjectPublicKeyInfo. A poll of implementers raised no objections because current implementations were not affected.

The label on the public key should not say how the key may be used. Those details belong somewhere else.

§4The Algorithm Identifier Rule

The third change rewrites the first paragraph of RFC 4055 Section 4.1 with the same reasoning. Whenever id-RSAES-OAEP is used in an AlgorithmIdentifier, the parameters MUST employ the RSAES-OAEP-params syntax. The old text said the parameters may be absent or present as subject public key information. Now they MUST be absent when used in the subjectPublicKeyInfo field, and they MUST still be present when used in the algorithm identifier associated with an encrypted value.

On a public key label the settings are left out. On an actual locked message the settings must be included.

§5Security Considerations

The security considerations of RFC 4055 still apply. In addition, if the RSAES-OAEP-params are negotiated, the negotiation mechanism needs to provide integrity for them. For example, an S/MIME agent can advertise its capabilities in the SMIMECapabilities attribute, which is either a signed attribute or a certificate extension.

If two sides agree on settings, nobody must be able to quietly change what they agreed on.

§6References

[RFC2119]RFC 2119Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.March 1997 [RFC4055]RFC 4055Schaad, 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.June 2005 [RFC4262]RFC 4262Santesson, S., "X.509 Certificate Extension for Secure/Multipurpose Internet Mail Extensions (S/MIME) Capabilities", RFC 4262, December 2005.December 2005 [RFC5751]RFC 5751Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification", RFC 5751, January 2010.January 2010