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/RFC 5756.
Copyright Notice
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document authors. All rights reserved.
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Provisions Relating to IETF Documents
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
Turner, et al. Standards Track [Page 1]
RFC 5756 RFC 4055 Update January 2010
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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 [RFC 4055] 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
[RFC 4055], while Section 4 updates the second paragraph in Section
4.1 of [RFC 4055]. "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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RFC 5756 RFC 4055 Update January 2010
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 [RFC 2119].
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.
Turner, et al. Standards Track [Page 3]
RFC 5756 RFC 4055 Update January 2010
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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RFC 5756 RFC 4055 Update January 2010
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 [RFC 4055] 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
[RFC 5751] or a certificate extension [RFC 4262].
6. References
6.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 4055] 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
[RFC 4262] Santesson, S., "X.509 Certificate Extension for
Secure/Multipurpose Internet Mail Extensions (S/MIME)
Capabilities", RFC 4262, December 2005.
[RFC 5751] 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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RFC 5756 RFC 4055 Update 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
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