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RFC 8608

BGPsec Algorithms, Key Formats, and Signature Formats

Pages: 21
Proposed STD
Obsoletes:  8208
Updates:  7935
Part 1 of 2 – Pages 1 to 11
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Internet Engineering Task Force (IETF)                         S. Turner
Request for Comments: 8608                                         sn3rd
Obsoletes: 8208                                              O. Borchert
Updates: 7935                                                       NIST
Category: Standards Track                                      June 2019
ISSN: 2070-1721


         BGPsec Algorithms, Key Formats, and Signature Formats

Abstract

   This document specifies the algorithms, algorithm parameters,
   asymmetric key formats, asymmetric key sizes, and signature formats
   used in BGPsec (Border Gateway Protocol Security).  This document
   updates RFC 7935 ("The Profile for Algorithms and Key Sizes for Use
   in the Resource Public Key Infrastructure") and obsoletes RFC 8208
   ("BGPsec Algorithms, Key Formats, and Signature Formats") by adding
   Documentation and Experimentation Algorithm IDs, correcting the range
   of unassigned algorithms IDs to fill the complete range, and
   restructuring the document for better reading.

   This document also includes example BGPsec UPDATE messages as well as
   the private keys used to generate the messages and the certificates
   necessary to validate those 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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8608.
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Copyright Notice

   Copyright (c) 2019 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
   (https://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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Changes from RFC 8208 . . . . . . . . . . . . . . . . . .   4
   2.  Algorithms  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Algorithm ID Types  . . . . . . . . . . . . . . . . . . .   4
     2.2.  Signature Algorithms  . . . . . . . . . . . . . . . . . .   6
       2.2.1.  Algorithm ID 0x01 (1) - (ECDSA P-256) . . . . . . . .   6
   3.  Asymmetric Key Pair Formats . . . . . . . . . . . . . . . . .   6
     3.1.  Asymmetric Key Pair for Algorithm ID 0x01 (1) - (ECDSA
           P-256)  . . . . . . . . . . . . . . . . . . . . . . . . .   6
       3.1.1.  Public Key Format . . . . . . . . . . . . . . . . . .   6
       3.1.2.  Private Key Format  . . . . . . . . . . . . . . . . .   7
   4.  Signature Formats . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Additional Requirements . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  12
     A.1.  Topology and Experiment Description . . . . . . . . . . .  12
     A.2.  Keys  . . . . . . . . . . . . . . . . . . . . . . . . . .  12
     A.3.  BGPsec IPv4 . . . . . . . . . . . . . . . . . . . . . . .  16
     A.4.  BGPsec IPv6 . . . . . . . . . . . . . . . . . . . . . . .  18
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21
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1.  Introduction

   This document specifies the following:

   o  the digital signature algorithm and parameters,

   o  the hash algorithm and parameters,

   o  the algorithm identifier assignment and classification,

   o  the public and private key formats, and

   o  the signature formats

   used by Resource Public Key Infrastructure (RPKI) Certification
   Authorities (CAs) and BGPsec (Border Gateway Protocol Security)
   speakers (i.e., routers).  CAs use these algorithms when processing
   requests for BGPsec Router Certificates [RFC8209].  Examples of when
   BGPsec routers use these algorithms include requesting BGPsec
   certificates [RFC8209], signing BGPsec UPDATE messages [RFC8205], and
   verifying signatures on BGPsec UPDATE messages [RFC8205].

   This document updates [RFC7935] to add support for a) a different
   algorithm for BGPsec certificate requests, which are issued only by
   BGPsec speakers; b) a different Subject Public Key Info format for
   BGPsec certificates, which is needed for the specified BGPsec
   signature algorithm; and c) different signature formats for BGPsec
   signatures, which are needed for the specified BGPsec signature
   algorithm.  The BGPsec certificates are differentiated from other
   RPKI certificates by the use of the BGPsec Extended Key Usage as
   defined in [RFC8209].  BGPsec uses a different algorithm [RFC6090]
   [DSS] from the rest of the RPKI to provide similar security with
   smaller keys, making the certificates smaller; these algorithms also
   result in smaller signatures, which make the PDUs smaller.

   Appendix A (non-normative) contains example BGPsec UPDATE messages as
   well as the private keys used to generate the messages and the
   certificates necessary to validate the signatures.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.
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1.2.  Changes from RFC 8208

   This section describes the significant changes between [RFC8208] and
   this document.

   o  Added Section 2.1 containing Algorithm ID types.  Also, the
      interpretation of these IDs is described.

   o  Restructured Sections 2 and 3 to align with the corresponding
      algorithm suite identifier value.

   o  Corrected the range for unassigned algorithm suite identifier
      values.

   o  Added Documentation algorithm suite identifier values.

   o  Added Experimentation algorithm suite identifier values.

   o  Changed the next-hop IP in Appendix A's IPv6 example to use a
      private usage IPv6 address.

2.  Algorithms

   The algorithms used to compute signatures on CA certificates, BGPsec
   Router Certificates, and Certificate Revocation Lists (CRLs) are as
   specified in Section 2 of [RFC7935].  This section addresses
   algorithms used by BGPsec [RFC8205] [DSS].  For example, these
   algorithms are used by BGPsec routers to sign and verify BGPsec
   UPDATE messages.  To identify which algorithm is used, the BGPsec
   UPDATE message contains the corresponding algorithm ID in each
   Signature_Block of the BGPsec UPDATE message.

2.1.  Algorithm ID Types

   Algorithms in BGPsec UPDATE messages are identified by the Algorithm
   Suite Identifier field (algorithm ID) within the Signature_Block (see
   Section 3.2 of [RFC8205]).

   This document specifies five types of Algorithm IDs:

   o  Reserved Algorithm ID

      Reserved algorithm IDs are the values 0x00 (0) and 0xFF (255).
      These IDs MUST NOT be used in a Signature_Block, and if
      encountered, the router MUST treat BGPsec UPDATE messages as
      malformed [RFC4271].
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   o  Signature Algorithm ID

      Signature algorithms are defined in Section 2.2 of this document.
      Processing of BGPsec UPDATE signing and validation using signature
      algorithms is described at length in Sections 4.2 and 5.2 of
      [RFC8205].

   o  Unassigned Algorithm ID

      This type of Algorithm ID is free for future assignments and MUST
      NOT be used until an algorithm is officially assigned (see
      Section 7).  In case a router encounters an unassigned algorithm
      ID in one of the Signature_Blocks of a BGPsec UPDATE message, the
      router SHOULD process the Signature_Block as an unsupported
      algorithm as specified in Section 5.2 of [RFC8205].

   o  Experimentation Algorithm ID

      Experimentation algorithm IDs span from 0xF7 (247) to 0xFA (250).
      To allow experimentation to accurately describe deployment
      examples, the use of publicly assigned algorithm IDs is
      inappropriate, and a reserved block of Experimentation algorithm
      IDs is required.  This ensures that experimentation does not clash
      with assigned algorithm IDs in deployed networks and mitigates the
      risks to operational integrity of the network through
      inappropriate use of experimentation to perform literal
      configuration of routing elements on production systems.  A router
      that encounters an algorithm ID of this type outside of an
      experimental network SHOULD treat it the same as an unsupported
      algorithm as specified in Section 5.2 of [RFC8205].

   o  Documentation Algorithm ID

      Documentation algorithm IDs span from 0xFB (251) to 0xFE (254).
      To allow documentation to accurately describe deployment examples,
      the use of publicly assigned algorithm IDs is inappropriate, and a
      reserved block of Documentation algorithm IDs is required.  This
      ensures that documentation does not clash with assigned algorithm
      IDs in deployed networks and mitigates the risks to operational
      integrity of the network through inappropriate use of
      documentation to perform literal configuration of routing elements
      on production systems.  A router that encounters an algorithm ID
      of this type SHOULD treat it the same as an unsupported algorithm
      as specified in Section 5.2 of [RFC8205].
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2.2.  Signature Algorithms

2.2.1.  Algorithm ID 0x01 (1) - (ECDSA P-256)

   o  The signature algorithm used MUST be the Elliptic Curve Digital
      Signature Algorithm (ECDSA) with curve P-256 [RFC6090] [DSS].

   o  The hash algorithm used MUST be SHA-256 [SHS].

   Hash algorithms are not identified by themselves in certificates or
   BGPsec UPDATE messages.  They are represented by an OID that combines
   the hash algorithm with the digital signature algorithm as follows:

   o  The ecdsa-with-SHA256 OID [RFC5480] MUST appear in the Public-Key
      Cryptography Standards #10 (PKCS #10) signatureAlgorithm field
      [RFC2986] or in the Certificate Request Message Format (CRMF)
      POPOSigningKey algorithm field [RFC4211]; where the OID is placed
      depends on the certificate request format generated.

   o  In BGPsec UPDATE messages, the ECDSA with SHA-256 algorithm suite
      identifier value 0x01 (1) (see Section 7) is included in the
      Signature_Block List's Algorithm Suite Identifier field.

3.  Asymmetric Key Pair Formats

   The key formats used to compute signatures on CA certificates, BGPsec
   Router Certificates, and CRLs are as specified in Section 3 of
   [RFC7935].  This section addresses key formats found in the BGPsec
   Router Certificate requests and in BGPsec Router Certificates.

3.1.  Asymmetric Key Pair for Algorithm ID 0x01 (1) - (ECDSA P-256)

   The ECDSA private keys used to compute signatures for certificate
   requests and BGPsec UPDATE messages MUST be associated with the P-256
   elliptic curve domain parameters [RFC5480].  The public key pair MUST
   use the uncompressed form.

3.1.1.  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:

   o  algorithm (an AlgorithmIdentifier type): The id-ecPublicKey OID
      MUST be used in the algorithm field, as specified in Section 2.1.1
      of [RFC5480].  The value for the associated parameters MUST be
      secp256r1, as specified in Section 2.1.1.1 of [RFC5480].
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   o  subjectPublicKey: ECPoint MUST be used to encode the certificate's
      subjectPublicKey field, as specified in Section 2.2 of [RFC5480].

3.1.2.  Private Key Format

   Local policy determines private key format.

4.  Signature Formats

   The structure for the certificate's and CRL's signature field MUST be
   as specified in Section 4 of [RFC7935]; this is the same format used
   by other RPKI certificates.  The structure for the certification
   request's and BGPsec UPDATE message's signature field MUST be as
   specified in Section 2.2.3 of [RFC3279].

5.  Additional Requirements

   It is anticipated that BGPsec 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.  This profile should be updated to specify such future
   requirements, when appropriate.

   The recommended procedures to implement such a transition of key
   sizes and algorithms are specified in [RFC6916].

6.  Security Considerations

   The security considerations of [RFC3279], [RFC5480], [RFC6090],
   [RFC7935], and [RFC8209] apply to certificates.  The security
   considerations of [RFC3279], [RFC6090], [RFC7935], and [RFC8209]
   apply to certification requests.  The security considerations of
   [RFC3279], [RFC6090], and [RFC8205] apply to BGPsec UPDATE messages.
   No new security considerations are introduced as a result of this
   specification.

7.  IANA Considerations

   The Internet Assigned Numbers Authority (IANA) has created the
   "BGPsec Algorithm Suites" registry in the Resource Public Key
   Infrastructure (RPKI) group.  The one-octet algorithm suite
   identifiers assigned by IANA identify the digest algorithm and
   signature algorithm used in the BGPsec Signature_Block List's
   Algorithm Suite Identifier field.

   Per [RFC8208], IANA registered a single algorithm suite identifier
   for the digest algorithm SHA-256 [SHS] and for the signature
   algorithm ECDSA on the P-256 curve [RFC6090] [DSS].  This identifier
Top   ToC   Page 8
   is still valid, and IANA has updated the registration to refer to
   this document.

   IANA has modified the range of the "Unassigned" address space from
   "0x2-0xEF" to "0x02-0xF6":

     Algorithm   Digest          Signature       Specification
     Suite       Algorithm       Algorithm       Pointer
     Identifier
   +------------+---------------+--------------+-----------------------+
   | 0x02-0xF6  | Unassigned    | Unassigned   |                       |
   +------------+---------------+--------------+-----------------------+

   In addition, IANA has registered the following address spaces for
   "Experimentation" and "Documentation":

     Algorithm   Digest            Signature         Specification
     Suite       Algorithm         Algorithm         Pointer
     Identifier
   +------------+-----------------+-----------------+------------------+
   | 0xF7-0xFA  | Experimentation | Experimentation | This document    |
   +------------+-----------------+-----------------+------------------+
   | 0xFB-0xFE  | Documentation   | Documentation   | This document    |
   +------------+-----------------+-----------------+------------------+

   The "BGPsec Algorithm Suites" registry in the RPKI group now contains
   the following values:

     Algorithm   Digest            Signature         Specification
     Suite       Algorithm         Algorithm         Pointer
     Identifier
   +------------+-----------------+-----------------+------------------+
   | 0x00       | Reserved        | Reserved        | This document    |
   +------------+-----------------+-----------------+------------------+
   | 0x01       | SHA-256         | ECDSA P-256     | [SHS] [DSS]      |
   |            |                 |                 | [RFC6090]        |
   |            |                 |                 | This document    |
   +------------+-----------------+-----------------+------------------+
   | 0x02-0xF6  | Unassigned      | Unassigned      |                  |
   +------------+-----------------+-----------------+------------------+
   | 0xF7-0xFA  | Experimentation | Experimentation | This document    |
   +------------+-----------------+-----------------+------------------+
   | 0xFB-0xFE  | Documentation   | Documentation   | This document    |
   +------------+-----------------+-----------------+------------------+
   | 0xFF       | Reserved        | Reserved        | This document    |
   +------------+-----------------+-----------------+------------------+
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   Future assignments are to be made using the Standards Action process
   defined in [RFC8126].  Assignments consist of the one-octet algorithm
   suite identifier value and the associated digest algorithm name and
   signature algorithm name.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2986]  Nystrom, M. and B. Kaliski, "PKCS #10: Certification
              Request Syntax Specification Version 1.7", RFC 2986,
              DOI 10.17487/RFC2986, November 2000,
              <https://www.rfc-editor.org/info/rfc2986>.

   [RFC3279]  Bassham, L., Polk, W., and R. Housley, "Algorithms and
              Identifiers for the Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 3279, DOI 10.17487/RFC3279, April
              2002, <https://www.rfc-editor.org/info/rfc3279>.

   [RFC4211]  Schaad, J., "Internet X.509 Public Key Infrastructure
              Certificate Request Message Format (CRMF)", RFC 4211,
              DOI 10.17487/RFC4211, September 2005,
              <https://www.rfc-editor.org/info/rfc4211>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [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, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5480]  Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
              "Elliptic Curve Cryptography Subject Public Key
              Information", RFC 5480, DOI 10.17487/RFC5480, March 2009,
              <https://www.rfc-editor.org/info/rfc5480>.
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   [RFC6090]  McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
              Curve Cryptography Algorithms", RFC 6090,
              DOI 10.17487/RFC6090, February 2011,
              <https://www.rfc-editor.org/info/rfc6090>.

   [RFC6916]  Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility
              Procedure for the Resource Public Key Infrastructure
              (RPKI)", BCP 182, RFC 6916, DOI 10.17487/RFC6916, April
              2013, <https://www.rfc-editor.org/info/rfc6916>.

   [RFC7935]  Huston, G. and G. Michaelson, Ed., "The Profile for
              Algorithms and Key Sizes for Use in the Resource Public
              Key Infrastructure", RFC 7935, DOI 10.17487/RFC7935,
              August 2016, <https://www.rfc-editor.org/info/rfc7935>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8205]  Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
              Specification", RFC 8205, DOI 10.17487/RFC8205, September
              2017, <https://www.rfc-editor.org/info/rfc8205>.

   [RFC8208]  Turner, S. and O. Borchert, "BGPsec Algorithms, Key
              Formats, and Signature Formats", RFC 8208,
              DOI 10.17487/RFC8208, September 2017,
              <https://www.rfc-editor.org/info/rfc8208>.

   [RFC8209]  Reynolds, M., Turner, S., and S. Kent, "A Profile for
              BGPsec Router Certificates, Certificate Revocation Lists,
              and Certification Requests", RFC 8209,
              DOI 10.17487/RFC8209, September 2017,
              <https://www.rfc-editor.org/info/rfc8209>.

   [DSS]      National Institute of Standards and Technology, "Digital
              Signature Standard (DSS)", NIST FIPS Publication 186-4,
              DOI 10.6028/NIST.FIPS.186-4, July 2013,
              <https://nvlpubs.nist.gov/nistpubs/FIPS/
              NIST.FIPS.186-4.pdf>.
Top   ToC   Page 11
   [SHS]      National Institute of Standards and Technology, "Secure
              Hash Standard (SHS)", NIST FIPS Publication 180-4,
              DOI 10.6028/NIST.FIPS.180-4, August 2015,
              <https://nvlpubs.nist.gov/nistpubs/FIPS/
              NIST.FIPS.180-4.pdf>.

8.2.  Informative References

   [RFC5398]  Huston, G., "Autonomous System (AS) Number Reservation for
              Documentation Use", RFC 5398, DOI 10.17487/RFC5398,
              December 2008, <https://www.rfc-editor.org/info/rfc5398>.

   [RFC6979]  Pornin, T., "Deterministic Usage of the Digital Signature
              Algorithm (DSA) and Elliptic Curve Digital Signature
              Algorithm (ECDSA)", RFC 6979, DOI 10.17487/RFC6979, August
              2013, <https://www.rfc-editor.org/info/rfc6979>.


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