Internet Engineering Task Force (IETF)                         G. Huston
Request for Comments: 6485                                         APNIC
Category: Standards Track                                  February 2012
ISSN: 2070-1721


             The Profile for Algorithms and Key Sizes for
         Use in the Resource Public Key Infrastructure (RPKI)

Abstract

  This document specifies the algorithms, algorithms' parameters,
  asymmetric key formats, asymmetric key size, and signature format for
  the Resource Public Key Infrastructure (RPKI) subscribers that
  generate digital signatures on certificates, Certificate Revocation
  Lists, and signed objects as well as for the relying parties (RPs)
  that verify these digital signatures.

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/rfc6485.

Copyright Notice

  Copyright (c) 2012 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.





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1.  Introduction

  This document specifies:

  *  the digital signature algorithm and parameters;
  *  the hash algorithm and parameters;
  *  the public and private key formats; and,
  *  the signature format

  used by Resource Public Key Infrastructure (RPKI) subscribers when
  they apply digital signatures to certificates, Certificate Revocation
  Lists (CRLs), and signed objects (e.g., Route Origin Authorizations
  (ROAs) and manifests).  Relying parties (RPs) also use the algorithms
  defined in this document to verify RPKI subscribers' digital
  signatures [RFC6480].

  This document is referenced by other RPKI profiles and
  specifications, including the RPKI Certificate Policy (CP) [RFC6484],
  the RPKI Certificate Profile [RFC6487], the SIDR Architecture
  [RFC6480], and the Signed Object Template for the RPKI [RFC6488].
  Familiarity with these documents is assumed.

1.1.  Terminology

  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.  Algorithms

  Two cryptographic algorithms are used in the RPKI:

     *  The signature algorithm used in certificates, CRLs, and signed
        objects is RSA Public-Key Cryptography Standards (PKCS) #1
        Version 1.5 (sometimes referred to as "RSASSA-PKCS1-v1_5") from
        Section 5 of [RFC4055].

     *  The hashing algorithm used in certificates, CRLs, and signed
        objects is SHA-256 [SHS].  The hashing algorithm is not
        identified by itself when used in certificates and CRLs, as
        they are combined with the digital signature algorithm (see
        below).

        When used in the Cryptographic Message Syntax (CMS) SignedData,
        the hash algorithm (in this case, the hash algorithm is
        sometimes called a message digest algorithm) is identified by
        itself.  For CMS SignedData, the object identifier and
        parameters for SHA-256 (as defined in [RFC5754]) MUST be used



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        when populating the digestAlgorithms and digestAlgorithm
        fields.

        NOTE: The exception to the above hashing algorithm is the use
        of SHA-1 [SHS] when Certification Authorities (CAs) generate
        authority and subject key identifiers [RFC6487].

  When used to generate and verify digital signatures the hash and
  digital signature algorithms are referred together, i.e., "RSA PKCS#1
  v1.5 with SHA-256" or more simply "RSA with SHA-256".  The Object
  Identifier (OID) sha256withRSAEncryption from [RFC4055] MUST be used.

  Locations for this OID are as follows:

     In the certificate, the OID appears in the signature and
     signatureAlgorithm fields [RFC4055];

     In the CRL, the OID appears in the signatureAlgorithm field
     [RFC4055];

     In CMS SignedData, the OID appears in each SignerInfo
     signatureAlgoithm field [RFC3370] using the OID from above; and,

     In a certification request, the OID appears in the PKCS #10
     signatureAlgorithm field [RFC2986] or in the Certificate Request
     Message Format (CRMF) POPOSigningKey signature field [RFC4211].

3.  Asymmetric Key Pair Formats

  The RSA key pairs used to compute the signatures MUST have a 2048-bit
  modulus and a public exponent (e) of 65,537.

3.1.  Public Key Format

  The subject's public key is included in subjectPublicKeyInfo
  [RFC5280].  It has two sub-fields: algorithm and subjectPublicKey.
  The values for the structures and their sub-structures follow:

  algorithm (which is an AlgorithmIdentifier type):
     The object identifier for RSA PKCS#1 v1.5 with SHA-256 MUST be
     used in the algorithm field, as specified in Section 5 of
     [RFC4055].  The value for the associated parameters from that
     clause MUST also be used for the parameters field.

  subjectPublicKey:
     RSAPublicKey MUST be used to encode the certificate's
     subjectPublicKey field, as specified in [RFC4055].




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3.2.  Private Key Format

  Local policy determines the private key format.

4.  Signature Format

  The structure for the certificate's signature field is as specified
  in Section 1.2 of [RFC4055].  The structure for the CMS SignedData's
  signature field is as specified in [RFC3370].

5.  Additional Requirements

  It is anticipated that the RPKI will require the adoption of updated
  key sizes and a different set of signature and hash algorithms over
  time, in order to maintain an acceptable level of cryptographic
  security to protect the integrity of signed products in the RPKI.
  This profile should be replaced to specify such future requirements,
  as and when appropriate.

  CAs and RPs SHOULD be capable of supporting a transition to allow for
  the phased introduction of additional encryption algorithms and key
  specifications, and also accommodate the orderly deprecation of
  previously specified algorithms and keys.  Accordingly, CAs and RPs
  SHOULD be capable of supporting multiple RPKI algorithm and key
  profiles simultaneously within the scope of such anticipated
  transitions.  The recommended procedures to implement such a
  transition of key sizes and algorithms is not specified in this
  document.

6.  Security Considerations

  The Security Considerations of [RFC4055], [RFC5280], and [RFC6487]
  apply to certificates and CRLs.  The Security Considerations of
  [RFC5754] apply to signed objects.  No new security threats are
  introduced as a result of this specification.

7.  Acknowledgments

  The author acknowledges the reuse in this document of material
  originally contained in working drafts of the RPKI Certificate Policy
  [RFC6484] and the resource certificate profile [RFC6487] documents.
  The co-authors of these two documents, namely Stephen Kent, Derrick
  Kong, Karen Seo, Ronald Watro, George Michaelson, and Robert Loomans,
  are acknowledged, with thanks.  The constraint on key size noted in
  this profile is the outcome of comments from Stephen Kent and review
  comments from David Cooper.  Sean Turner has provided additional
  review input to this document.




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9.  Normative References

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

  [RFC2986]  Nystrom, M. and B. Kaliski, "PKCS #10: Certification
             Request Syntax Specification Version 1.7", RFC 2986,
             November 2000.

  [RFC3370]  Housley, R., "Cryptographic Message Syntax (CMS)
             Algorithms", RFC 3370, August 2002.

  [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.

  [RFC4211]  Schaad, J., "Internet X.509 Public Key Infrastructure
             Certificate Request Message Format (CRMF)", RFC 4211,
             September 2005.

  [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
             Housley, R., and W. Polk, "Internet X.509 Public Key
             Infrastructure Certificate and Certificate Revocation List
             (CRL) Profile", RFC 5280, May 2008.

  [RFC5754]  Turner, S., "Using SHA2 Algorithms with Cryptographic
             Message Syntax", RFC 5754, January 2010.

  [RFC6480]  Lepinski, M. and S. Kent, "An Infrastructure to Support
             Secure Internet Routing", RFC 6480, February 2012.

  [RFC6484]  Kent, S., Kong, D., Seo, K., and R. Watro, "Certificate
             Policy (CP) for the Resource Public Key Infrastructure
             (RPKI)", BCP 173, RFC 6484, February 2012.

  [RFC6487]  Husotn, G., Michaelson, G., and R. Loomans, "A Profile for
             X.509 PKIX Resource Certificates", RFC 6487, February
             2012.

  [RFC6488]  Lepinski, M., Chi, A., and S. Kent, "Signed Object
             Template for the Resource Public Key Infrastructure
             (RPKI)", RFC 6488, February 2012.

  [SHS]      National Institute of Standards and Technology (NIST),
             "FIPS Publication 180-3: Secure Hash Standard (SHS)", FIPS
             Publication 180-3, October 2008.



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Author's Address

  Geoff Huston
  APNIC

  EMail: [email protected]













































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