SIDR                                                           G. Huston
Internet-Draft                                                     APNIC
Intended status: Informational                              May 16, 2010
Expires: November 17, 2010

 A Profile for Algorithms and Key Sizes for use in the Resource Public
                           Key Infrastructure


   This document defines a profile for the algorithm and key size to be
   used for signatures applied to certificates, Certificate Revocation
   Lists, and signed objects in the context of the Resource Public Key

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   This Internet-Draft will expire on November 17, 2010.

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1.  Introduction

   This document defines a profile for the algorithm and key size to be
   used for signatures applied to certificates, Certificate Revocation
   Lists (CRLs), and signed objects in the context of the Resource
   Public Key Infrastructure (RPKI) [I-D.ietf-sidr-arch].

   This section of the profile is specified in a distinct profile
   document, referenced by the RPKI Certificate Policy (CP)
   [I-D.ietf-sidr-cp] and the RPKI Certificate Profile
   [I-D.ietf-sidr-res-certs], in order to allow for a degree of
   algorithm and key agility in the RPKI, while permitting some longer
   term stability in the CP and Certificate Profile specifications.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119.

2.  Algorithm and Key Size

   This profile specifies the use of RSASSA-PKCS1-v1_5 [RFC3447] with
   the SHA-256 hash algorithm to compute the signature of certificates,
   CRLs, and signed objects in the context of the RPKI.  Accordingly,
   the OID value in the RPKI for such signatures MUST be
   1.2.840.113549.1.1.11 (sha256WithRSAEncryption).  The RSA key pairs
   used to compute the signatures MUST have a 2048-bit modulus and a
   public exponent (e) of 65,537.

   In order to facilitate a potential need to transition to stronger
   cryptographic algorithms in the future, Certification Authorities
   (CAs) and Relying Parties (RPs) SHOULD be able to generate and verify
   RSASSA-PKCS1-v1_5 signatures using the SHA-512 hash algorithm and RSA
   key sizes of 3072 and 4096 bits.

3.  Future Upates

   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 updated 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 accomodate the orderly deprecation of

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   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

   Note: This document specifies the current algorithm requirements for
   the RPKI.  The document acknowledges a requirement for algorithm
   agility, both in terms of larger key sizes in conjunction with the
   current algorithms, and transition to other algorithms.  It is noted
   that the SIDR architecture is one where each CA is required to
   generate signed material that may be validated by the entire
   collection of Relying Parties.  This architectural requirement
   precludes the use of any negotiation between a CA and a RP as to the
   algorithm to use for signed products in the RPKI.  This constraint
   implies that any transition of key size or algorithm will require a
   phased approach with the concurrent support of both old and new
   algorithms until such time as it is deemed that all RPs can support
   the new algorithm.  Given that there is no accommodation for multiple
   signature algorithms in the current collection of RPKI
   specifications, either the colelction of RPKI specifications will
   require subsequent revision to support the use of multiple signature
   algorithms within the specifications of signed objects in the RPKI,
   which itself poses a transition issue, or all such form of algorithm
   transition will require the construction and operation of a parallel
   RPKI structure that is entirely distinct from the "current" RPKI
   structure by virtue of its exclusive use of a "new" algorithm for
   signature generation.  The latter option, that of the concurrent
   operation of parallel RPKI structures, poses some complex issues in
   terms of synchronisation of actions across the set of RPKI CAs, as
   well as issues of consistency and coherency in the operation of
   multiple parallel RPKI frameworks, as well as the uncertainties
   associated with a global determination of when any such transition
   can be considered "complete".  The alternate approach, of allowing
   multiple signature algorithms in the RPKI certificate profile, and in
   the specification of CMS signatures as used in manifests, ROAS, other
   signed objects, and in the provisioning protocol, allows for
   algorithm transition to occur within a single RPKI framework, and
   allows for individual CAs to commence use of multiple algorithms in a
   piecemeal fashion without reliance on the algorithm transition of the
   immediate superior CA and without a forced synchronisation of
   algorithm transition with subordinate CAs.  In the light of this
   consideration, this document recommends the comprehensive revision of
   the existing RPKI specification and architecture documents to include
   provision for multiple signatures with multiple algorithms in order
   to support an orderly transition to longer key sizes and to other
   signature algorithms in the RPKI.

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4.  Security Considerations

   The Security Considerations of [RFC3779], [RFC5280], and [RFC4055]
   apply to signatures as defined by this profile, and their use.

   Algorithm transition poses some particular security issues, relating
   to potential vulnerabilities in the parallel operation of an RPKI
   framework where a potentially compromised algorithm remains in use
   beyond a reasonable time for retirement.  These issues should be
   considered in detail in a future version of this document.

5.  IANA Considerations

   [There are no IANA considerations in this document.]

6.  Acknowledgments

   The author acknowledges the re-use in this draft of material
   originally contained in working drafts the RPKI Certificate Policy
   and Resource Certificate profile 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

7.  Normative References

              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch (work in
              progress), July 2009.

              Seo, K., Watro, R., Kong, D., and S. Kent, "Certificate
              Policy (CP) for the Resource PKI (RPKI)",
              draft-ietf-sidr-cp (work in progress), July 2009.

              Husotn, G., Michaelson, G., and R. Loomans, "A Profile for
              X.509 PKIX Resource Certificates",
              draft-ietf-sidr-res-certs (work in progress),
              February 2008.

   [RFC3447]  Jonsson, J. and B. Kaliski, "Public-Key Cryptography

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              Standards (PKCS) #1: RSA Cryptography Specifications
              Version 2.1", RFC 3447, February 2003.

   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779, June 2004.

   [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.

   [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.

Author's Address

   Geoff Huston
   Asia Pacific Network Information Centre


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