Network Working Group                                    S. Blake-Wilson
Request for Comments: 3278                                      D. Brown
Category: Informational                                    Certicom Corp
                                                              P. Lambert
                                                   Cosine Communications
                                                              April 2002

Use of Elliptic Curve Cryptography (ECC) Algorithms
in Cryptographic Message Syntax (CMS)

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

Abstract

   This document describes how to use Elliptic Curve Cryptography (ECC)
   public-key algorithms in the Cryptographic Message Syntax (CMS).  The
   ECC algorithms support the creation of digital signatures and the
   exchange of keys to encrypt or authenticate content.  The definition
   of the algorithm processing is based on the ANSI X9.62 standard,
   developed by the ANSI X9F1 working group, the IEEE 1363 standard, and
   the SEC 1 standard.

   The readers attention is called to the Intellectual Property Rights
   section at the end of this document.

   1  Introduction ................................................... 2
      1.1  Requirements terminology .................................. 3
   2  SignedData using ECC ..........................................  3
      2.1  SignedData using ECDSA ...................................  3
           2.1.1  Fields of the SignedData ..........................  3
           2.1.2  Actions of the sending agent ......................  4
           2.1.3  Actions of the receiving agent ....................  4
   3  EnvelopedData using ECC .......................................  4
      3.1  EnvelopedData using ECDH .................................  5
           3.1.1  Fields of KeyAgreeRecipientInfo ...................  5
           3.1.2  Actions of the sending agent ......................  5
           3.1.3  Actions of the receiving agent ....................  6
      3.2  EnvelopedData using 1-Pass ECMQV .........................  6
           3.2.1  Fields of KeyAgreeRecipientInfo ...................  6
           3.2.2  Actions of the sending agent ......................  7
           3.2.3  Actions of the receiving agent ....................  7
   4  AuthenticatedData using ECC ............ ......................  8
      4.1  AuthenticatedData using 1-pass ECMQV .....................  8
           4.1.1  Fields of KeyAgreeRecipientInfo ...................  8
           4.1.2  Actions of the sending agent ......................  8
           4.1.3  Actions of the receiving agent ....................  8
   5  Recommended Algorithms and Elliptic Curves ....................  9
   6  Certificates using ECC ........................................  9
   7  SMIMECapabilities Attribute and ECC ...........................  9
   8  ASN.1 Syntax .................................................. 10
      8.1  Algorithm identifiers .................................... 10
      8.2  Other syntax ............................................. 11
   9  Summary ....................................................... 12
   References ....................................................... 13
   Security Considerations .......................................... 14
   Intellectual Property Rights ..................................... 14
   Acknowledgments .................................................. 15
   Authors' Addresses ............................................... 15
   Full Copyright Statement ......................................... 16

1 Introduction

   The Cryptographic Message Syntax (CMS) is cryptographic algorithm
   independent.  This specification defines a profile for the use of
   Elliptic Curve Cryptography (ECC) public key algorithms in the CMS.
   The ECC algorithms are incorporated into the following CMS content
   types:

      -  'SignedData' to support ECC-based digital signature methods
         (ECDSA) to sign content

      -  'EnvelopedData' to support ECC-based public-key agreement
         methods (ECDH and ECMQV) to generate pairwise key-encryption
         keys to encrypt content-encryption keys used for content
         encryption

      -  'AuthenticatedData' to support ECC-based public-key agreement
         methods (ECMQV) to generate pairwise key-encryption keys to
         encrypt MAC keys used for content authentication and integrity

   Certification of EC public keys is also described to provide public-
   key distribution in support of the specified techniques.

1.1 Requirements 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 BCP 14, RFC 2119
   [MUST].

2 SignedData using ECC

This section describes how to use ECC algorithms with the CMS
SignedData format to sign data.

2.1 SignedData using ECDSA

   This section describes how to use the Elliptic Curve Digital
   Signature Algorithm (ECDSA) with SignedData.  ECDSA is specified in
   [X9.62].  The method is the elliptic curve analog of the Digital
   Signature Algorithm (DSA) [FIPS 186-2].

   In an implementation that uses ECDSA with CMS SignedData, the
   following techniques and formats MUST be used.

2.1.1 Fields of the SignedData

   When using ECDSA with SignedData, the fields of SignerInfo are as in
   [CMS], but with the following restrictions:

      digestAlgorithm MUST contain the algorithm identifier sha-1 (see
      Section 8.1) which identifies the SHA-1 hash algorithm.

      signatureAlgorithm contains the algorithm identifier ecdsa-with-
      SHA1 (see Section 8.1) which identifies the ECDSA signature
      algorithm.

      signature MUST contain the DER encoding (as an octet string) of a
      value of the ASN.1 type ECDSA-Sig-Value (see Section 8.2).

   When using ECDSA, the SignedData certificates field MAY include the
   certificate(s) for the EC public key(s) used in the generation of the
   ECDSA signatures in SignedData.  ECC certificates are discussed in
   Section 6.

2.1.2 Actions of the sending agent

   When using ECDSA with SignedData, the sending agent uses the message
   digest calculation process and signature generation process for
   SignedData that are specified in [CMS].  To sign data, the sending
   agent uses the signature method specified in [X9.62, Section 5.3]
   with the following exceptions:

      -  In [X9.62, Section 5.3.1], the integer "e" is instead
         determined by converting the message digest generated according
         to [CMS, Section 5.4] to an integer using the data conversion
         method in [X9.62, Section 4.3.2].

   The sending agent encodes the resulting signature using the ECDSA-
   Sig-Value syntax (see Section 8.2) and places it in the SignerInfo
   signature field.

2.1.3 Actions of the receiving agent

   When using ECDSA with SignedData, the receiving agent uses the
   message digest calculation process and signature verification process
   for SignedData that are specified in [CMS].  To verify SignedData,
   the receiving agent uses the signature verification method specified
   in [X9.62, Section 5.4] with the following exceptions:

      -  In [X9.62, Section 5.4.1] the integer "e'" is instead
         determined by converting the message digest generated according
         to [CMS, Section 5.4] to an integer using the data conversion
         method in [X9.62, Section 4.3.2].

   In order to verify the signature, the receiving agent retrieves the
   integers r and s from the SignerInfo signature field of the received
   message.

3 EnvelopedData using ECC Algorithms

This section describes how to use ECC algorithms with the CMS
EnvelopedData format.

3.1 EnvelopedData using (ephemeral-static) ECDH

   This section describes how to use the ephemeral-static Elliptic Curve
   Diffie-Hellman (ECDH) key agreement algorithm with EnvelopedData.
   Ephemeral-static ECDH is specified in [SEC1] and [IEEE1363].
   Ephemeral-static ECDH is the the elliptic curve analog of the
   ephemeral-static Diffie-Hellman key agreement algorithm specified
   jointly in the documents [CMS, Section 12.3.1.1] and [CMS-DH].

   In an implementation that uses ECDH with CMS EnvelopedData with key
   agreement, the following techniques and formats MUST be used.

3.1.1 Fields of KeyAgreeRecipientInfo

   When using ephemeral-static ECDH with EnvelopedData, the fields of
   KeyAgreeRecipientInfo are as in [CMS], but with the following
   restrictions:

      originator MUST be the alternative originatorKey.  The
      originatorKey algorithm field MUST contain the id-ecPublicKey
      object identifier (see Section 8.1) with NULL parameters.  The
      originatorKey publicKey field MUST contain the DER-encoding of a
      value of the ASN.1 type ECPoint (see Section 8.2), which
      represents the sending agent's ephemeral EC public key.

      keyEncryptionAlgorithm MUST contain the dhSinglePass-stdDH-
      sha1kdf-scheme object identifier (see Section 8.1) if standard
      ECDH primitive is used, or the dhSinglePass-cofactorDH-sha1kdf-
      scheme object identifier (see Section 8.1) if the cofactor ECDH
      primitive is used.  The parameters field contains
      KeyWrapAlgorithm.  The KeyWrapAlgorithm is the algorithm
      identifier that indicates the symmetric encryption algorithm used
      to encrypt the content-encryption key (CEK) with the key-
      encryption key (KEK).

3.1.2 Actions of the sending agent

   When using ephemeral-static ECDH with EnvelopedData, the sending
   agent first obtains the recipient's EC public key and domain
   parameters (e.g. from the recipient's certificate).  The sending
   agent then determines an integer "keydatalen", which is the
   KeyWrapAlgorithm symmetric key-size in bits, and also a bit string
   "SharedInfo", which is the DER encoding of ECC-CMS-SharedInfo (see
   Section 8.2).  The sending agent then performs the key deployment and
   the key agreement operation of the Elliptic Curve Diffie-Hellman
   Scheme specified in [SEC1, Section 6.1].  As a result the sending
   agent obtains:

      -  an ephemeral public key, which is represented as a value of the
         type ECPoint (see Section 8.2), encapsulated in a bit string
         and placed in the KeyAgreeRecipientInfo originator field, and

      -  a shared secret bit string "K", which is used as the pairwise
         key-encryption key for that recipient, as specified in [CMS].

3.1.3 Actions of the receiving agent

   When using ephemeral-static ECDH with EnvelopedData, the receiving
   agent determines the bit string "SharedInfo", which is the DER
   encoding of ECC-CMS-SharedInfo (see Section 8.2), and the integer
   "keydatalen" from the key-size, in bits, of the KeyWrapAlgorithm.
   The receiving agent retrieves the ephemeral EC public key from the
   bit string KeyAgreeRecipientInfo originator, with a value of the type
   ECPoint (see Section 8.2) encapsulated as a bit string.  The
   receiving agent performs the key agreement operation of the Elliptic
   Curve Diffie-Hellman Scheme specified in [SEC1, Section 6.1].  As a
   result, the receiving agent obtains a shared secret bit string "K",
   which is used as the pairwise key-encryption key to unwrap the CEK.

3.2 EnvelopedData using 1-Pass ECMQV

   This section describes how to use the 1-Pass elliptic curve MQV
   (ECMQV) key agreement algorithm with EnvelopedData.  ECMQV is
   specified in [SEC1] and [IEEE1363].  Like the KEA algorithm [CMS-
   KEA], 1-Pass ECMQV uses three key pairs: an ephemeral key pair, a
   static key pair of the sending agent, and a static key pair of the
   receiving agent.  An advantage of using 1-Pass ECMQV is that it can
   be used with both EnvelopedData and AuthenticatedData.

   In an implementation that uses 1-Pass ECMQV with CMS EnvelopedData
   with key agreement, the following techniques and formats MUST be
   used.

3.2.1 Fields of KeyAgreeRecipientInfo

   When using 1-Pass ECMQV with EnvelopedData, the fields of
   KeyAgreeRecipientInfo are:

      originator identifies the static EC public key of the sender.  It
      SHOULD be one of the alternatives, issuerAndSerialNumber or
      subjectKeyIdentifier, and point to one of the sending agent's
      certificates.

      ukm MUST be present.  The ukm field MUST contain an octet string
      which is the DER encoding of the type MQVuserKeyingMaterial (see
      Section 8.2).  The MQVuserKeyingMaterial ephemeralPublicKey

      algorithm field MUST contain the id-ecPublicKey object identifier
      (see Section 8.1) with NULL parameters field.  The
      MQVuserKeyingMaterial ephemeralPublicKey publicKey field MUST
      contain the DER-encoding of the ASN.1 type ECPoint (see Section
      8.2) representing sending agent's ephemeral EC public key.  The
      MQVuserKeyingMaterial addedukm field, if present, SHOULD contain
      an octet string of additional user keying material of the sending
      agent.

      keyEncryptionAlgorithm MUST be the mqvSinglePass-sha1kdf-scheme
      algorithm identifier (see Section 8.1), with the parameters field
      KeyWrapAlgorithm. The KeyWrapAlgorithm indicates the symmetric
      encryption algorithm used to encrypt the CEK with the KEK
      generated using the 1-Pass ECMQV algorithm.

3.2.2 Actions of the sending agent

   When using 1-Pass ECMQV with EnvelopedData, the sending agent first
   obtains the recipient's EC public key and domain parameters, (e.g.
   from the recipient's certificate) and checks that the domain
   parameters are the same.  The sending agent then determines an
   integer "keydatalen", which is the KeyWrapAlgorithm symmetric key-
   size in bits, and also a bit string "SharedInfo", which is the DER
   encoding of ECC-CMS-SharedInfo (see Section 8.2).  The sending agent
   then performs the key deployment and key agreement operations of the
   Elliptic Curve MQV Scheme specified in [SEC1, Section 6.2].  As a
   result, the sending agent obtains:

      -  an ephemeral public key, which is represented as a value of
         type ECPoint (see Section 8.2), encapsulated in a bit string,
         placed in an MQVuserKeyingMaterial ephemeralPublicKey publicKey
         field (see Section 8.2), and

      -  a shared secret bit string "K", which is used as the pairwise
         key-encryption key for that recipient, as specified in [CMS].

   The ephemeral public key can be re-used with an AuthenticatedData for
   greater efficiency.

3.2.3 Actions of the receiving agent

   When using 1-Pass ECMQV with EnvelopedData, the receiving agent
   determines the bit string "SharedInfo", which is the DER encoding of
   ECC-CMS-SharedInfo (see Section 8.2), and the integer "keydatalen"
   from the key-size, in bits, of the KeyWrapAlgorithm.  The receiving
   agent then retrieves the static and ephemeral EC public keys of the
   originator, from the originator and ukm fields as described in
   Section 3.2.1, and its static EC public key identified in the rid

   field and checks that the domain parameters are the same.  The
   receiving agent then performs the key agreement operation of the
   Elliptic Curve MQV Scheme [SEC1, Section 6.2].  As a result, the
   receiving agent obtains a shared secret bit string "K" which is used
   as the pairwise key-encryption key to unwrap the CEK.

4 AuthenticatedData using ECC

   This section describes how to use ECC algorithms with the CMS
   AuthenticatedData format.  AuthenticatedData lacks non-repudiation,
   and so in some instances is preferable to SignedData.  (For example,
   the sending agent might not want the message to be authenticated when
   forwarded.)

4.1 AuthenticatedData using 1-pass ECMQV

   This section describes how to use the 1-Pass elliptic curve MQV
   (ECMQV) key agreement algorithm with AuthenticatedData.  ECMQV is
   specified in [SEC1].  An advantage of using 1-Pass ECMQV is that it
   can be used with both EnvelopedData and AuthenticatedData.

4.1.1 Fields of the KeyAgreeRecipientInfo

   The AuthenticatedData KeyAgreeRecipientInfo fields are used in the
   same manner as the fields for the corresponding EnvelopedData
   KeyAgreeRecipientInfo fields of Section 3.2.1 of this document.

4.1.2 Actions of the sending agent

   The sending agent uses the same actions as for EnvelopedData with 1-
   Pass ECMQV, as specified in Section 3.2.2 of this document.

   The ephemeral public key can be re-used with an EnvelopedData for
   greater efficiency.

   Note: if there are multiple recipients, an attack is possible where
   one recipient modifies the content without other recipients noticing
   [BON].  A sending agent who is concerned with such an attack SHOULD
   use a separate AuthenticatedData for each recipient.

4.1.3 Actions of the receiving agent

   The receiving agent uses the same actions as for EnvelopedData with
   1-Pass ECMQV, as specified in Section 3.2.3 of this document.

   Note: see Note in Section 4.1.2.

5 Recommended Algorithms and Elliptic Curves

   Implementations of this specification MUST implement either
   SignedData with ECDSA or EnvelopedData with ephemeral-static ECDH.
   Implementations of this specification SHOULD implement both
   SignedData with ECDSA and EnvelopedData with ephemeral-static ECDH.
   Implementations MAY implement the other techniques specified, such as
   AuthenticatedData and 1-Pass ECMQV.

   Furthermore, in order to encourage interoperability, implementations
   SHOULD use the elliptic curve domain parameters specified by ANSI
   [X9.62], NIST [FIPS-186-2] and SECG [SEC2].

6 Certificates using ECC

   Internet X.509 certificates [PKI] can be used in conjunction with
   this specification to distribute agents' public keys.  The use of ECC
   algorithms and keys within X.509 certificates is specified in [PKI-
   ALG].

7 SMIMECapabilities Attribute and ECC

   A sending agent MAY announce to receiving agents that it supports one
   or more of the ECC algorithms in this document by using the
   SMIMECapabilities signed attribute [MSG, Section 2.5.2].

   The SMIMECapability value to indicate support for the ECDSA signature
   algorithm is the SEQUENCE with the capabilityID field containing the
   object identifier ecdsa-with-SHA1 with NULL parameters.  The DER
   encoding is:

30 0b 06 07 2a 86 48 ce 3d 04 01 05 00

   The SMIMECapability capabilityID object identifiers for the supported
   key agreement algorithms in this document are dhSinglePass-stdDH-
   sha1kdf-scheme, dhSinglePass-cofactorDH-sha1kdf-scheme, and
   mqvSinglePass-sha1kdf-scheme.  For each of these SMIMECapability
   SEQUENCEs, the parameters field is present and indicates the
   supported key-encryption algorithm with the KeyWrapAlgorithm
   algorithm identifier.  The DER encodings that indicate capability of
   the three key agreement algorithms with CMS Triple-DES key wrap are:

      30 1c 06 09  2b 81 05 10   86 48 3f 00  02 30 0f 06
      0b 2a 86 48  86 f7 0d 01   09 10 03 06  05 00

   for ephemeral-static ECDH,

      30 1c 06 09  2b 81 05 10   86 48 3f 00  03 30 0f 06
      0b 2a 86 48  86 f7 0d 01   09 10 03 06  05 00

   for ephemeral-static ECDH with cofactor method, and

      30 1c 06 09  2b 81 05 10   86 48 3f 00  10 30 0f 06
      0b 2a 86 48  86 f7 0d 01   09 10 03 06  05 00

   for ECMQV.

8 ASN.1 Syntax

The ASN.1 syntax used in this document is gathered in this section
for reference purposes.

8.1 Algorithm identifiers

   The algorithm identifiers used in this document are taken from
   [X9.62], [SEC1] and [SEC2].

   The following object identifier indicates the hash algorithm used in
   this document:

      sha-1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
         oiw(14) secsig(3) algorithm(2) 26 }

   The following object identifier is used in this document to indicate
   an elliptic curve public key:

      id-ecPublicKey OBJECT IDENTIFIER ::= { ansi-x9-62 keyType(2) 1 }

   where

      ansi-x9-62 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
        10045 }

   When the object identifier id-ecPublicKey is used here with an
   algorithm identifier, the associated parameters contain NULL.

   The following object identifier indicates the digital signature
   algorithm used in this document:

      ecdsa-with-SHA1 OBJECT IDENTIFIER ::= { ansi-x9-62 signatures(4)
         1 }

   When the object identifier ecdsa-with-SHA1 is used within an
   algorithm identifier, the associated parameters field contains NULL.

   The following object identifiers indicate the key agreement
   algorithms used in this document:

      dhSinglePass-stdDH-sha1kdf-scheme OBJECT IDENTIFIER ::= {
         x9-63-scheme 2}

      dhSinglePass-cofactorDH-sha1kdf-scheme OBJECT IDENTIFIER ::= {
         x9-63-scheme 3}

      mqvSinglePass-sha1kdf-scheme OBJECT IDENTIFIER ::= {
         x9-63-scheme 16}

   where

      x9-63-scheme OBJECT IDENTIFIER ::= { iso(1)
         identified-organization(3) tc68(133) country(16) x9(840)
         x9-63(63) schemes(0) }

   When the object identifiers are used here within an algorithm
   identifier, the associated parameters field contains the CMS
   KeyWrapAlgorithm algorithm identifier.

8.2 Other syntax

   The following additional syntax is used here.

   When using ECDSA with SignedData, ECDSA signatures are encoded using
   the type:

      ECDSA-Sig-Value ::= SEQUENCE {
         r INTEGER,
         s INTEGER }

   ECDSA-Sig-Value is specified in [X9.62].  Within CMS, ECDSA-Sig-Value
   is DER-encoded and placed within a signature field of SignedData.

   When using ECDH and ECMQV with EnvelopedData and AuthenticatedData,
   ephemeral and static public keys are encoded using the type ECPoint.

      ECPoint ::= OCTET STRING

   When using ECMQV with EnvelopedData and AuthenticatedData, the
   sending agent's ephemeral public key and additional keying material
   are encoded using the type:

      MQVuserKeyingMaterial ::= SEQUENCE {
         ephemeralPublicKey OriginatorPublicKey,
         addedukm [0] EXPLICIT UserKeyingMaterial OPTIONAL  }

   The ECPoint syntax in used to represent the ephemeral public key and
   placed in the ephemeralPublicKey field.  The additional user keying
   material is placed in the addedukm field.  Then the
   MQVuserKeyingMaterial value is DER-encoded and placed within a ukm
   field of EnvelopedData or AuthenticatedData.

   When using ECDH or ECMQV with EnvelopedData or AuthenticatedData, the
   key-encryption keys are derived by using the type:

      ECC-CMS-SharedInfo ::= SEQUENCE {
         keyInfo AlgorithmIdentifier,
         entityUInfo [0] EXPLICIT OCTET STRING OPTIONAL,
         suppPubInfo [2] EXPLICIT OCTET STRING   }

   The fields of ECC-CMS-SharedInfo are as follows:

      keyInfo contains the object identifier of the key-encryption
      algorithm (used to wrap the CEK) and NULL parameters.

      entityUInfo optionally contains additional keying material
      supplied by the sending agent.  When used with ECDH and CMS, the
      entityUInfo field contains the octet string ukm.  When used with
      ECMQV and CMS, the entityUInfo contains the octet string addedukm
      (encoded in MQVuserKeyingMaterial).

      suppPubInfo contains the length of the generated KEK, in bits,
      represented as a 32 bit number, as in [CMS-DH].  (E.g. for 3DES it
      would be 00 00 00 c0.)

   Within CMS, ECC-CMS-SharedInfo is DER-encoded and used as input to
   the key derivation function, as specified in [SEC1, Section 3.6.1].
   Note that ECC-CMS-SharedInfo differs from the OtherInfo specified in
   [CMS-DH].  Here, a counter value is not included in the keyInfo field
   because the key derivation function specified in [SEC1, Section
   3.6.1] ensures that sufficient keying data is provided.

9 Summary

   This document specifies how to use ECC algorithms with the S/MIME
   CMS.  Use of ECC algorithm within CMS can result in reduced
   processing requirements for S/MIME agents, and reduced bandwidth for
   CMS messages.

References

   [X9.62]      ANSI X9.62-1998, "Public Key Cryptography For The
                Financial Services Industry: The Elliptic Curve Digital
                Signature Algorithm (ECDSA)", American National
                Standards Institute, 1999.

   [PKI-ALG]    Bassham, L., Housley R. and W. Polk, "Algorithms and
                Identifiers for the Internet X.509 Public Key
                Infrastructure Certificate and CRL Profile", RFC 3279,
                April 2002.

   [BON]        D. Boneh, "The Security of Multicast MAC", Presentation
                at Selected Areas of Cryptography 2000, Center for
                Applied Cryptographic Research, University of Waterloo,
                2000.  Paper version available from
                http://crypto.stanford.edu/~dabo/papers/mmac.ps

   [MUST]       Bradner, S., "Key Words for Use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.

   [FIPS-180]   FIPS 180-1, "Secure Hash Standard", National Institute
                of Standards and Technology, April 17, 1995.

   [FIPS-186-2] FIPS 186-2, "Digital Signature Standard", National
                Institute of Standards and Technology, 15 February 2000.

   [PKI]        Housley, R., Polk, W., Ford, W. and D. Solo, "Internet
                X.509 Public Key Infrastructure Certificate and
                Certificate Revocation List (CRL) Profile", RFC 3280,
                April 2002.

   [CMS]        Housley, R., "Cryptographic Message Syntax", RFC 2630,
                June 1999.

   [IEEE1363]   IEEE P1363, "Standard Specifications for Public Key
                Cryptography", Institute of Electrical and Electronics
                Engineers, 2000.

   [K]          B. Kaliski, "MQV Vulnerabilty", Posting to ANSI X9F1 and
                IEEE P1363 newsgroups, 1998.

   [LMQSV]      L. Law, A. Menezes, M. Qu, J. Solinas and S. Vanstone,
                "An efficient protocol for authenticated key agreement",
                Technical report CORR 98-05, University of Waterloo,
                1998.

   [CMS-KEA]    Pawling, J., "CMS KEA and SKIPJACK Conventions", RFC
                2876, July 2000.

   [MSG]        Ramsdell, B., "S/MIME Version 3 Message Specification",
                RFC 2633, June 1999.

   [CMS-DH]     Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC
                2631, June 1999.

   [SEC1]       SECG, "Elliptic Curve Cryptography", Standards for
                Efficient Cryptography Group, 2000. Available from
                www.secg.org/collateral/sec1.pdf.

   [SEC2]       SECG, "Recommended Elliptic Curve Domain Parameters",
                Standards for Efficient Cryptography Group, 2000.
                Available from www.secg.org/collateral/sec2.pdf.

Security Considerations

   This specification is based on [CMS], [X9.62] and [SEC1] and the
   appropriate security considerations of those documents apply.

   In addition, implementors of AuthenticatedData should be aware of the
   concerns expressed in [BON] when using AuthenticatedData to send
   messages to more than one recipient.  Also, users of MQV should be
   aware of the vulnerability in [K].

   When 256, 384, and 512 bit hash functions succeed SHA-1 in future
   revisions of [FIPS], [FIPS-186-2], [X9.62] and [SEC1], then they can
   similarly succeed SHA-1 in a future revision of this document.

Intellectual Property Rights

   The IETF has been notified of intellectual property rights claimed in
   regard to the specification contained in this document.  For more
   information, consult the online list of claimed rights
   (http://www.ietf.org/ipr.html).

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP 11. Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to

   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

Acknowledgments

   The methods described in this document are based on work done by the
   ANSI X9F1 working group.  The authors wish to extend their thanks to
   ANSI X9F1 for their assistance.  The authors also wish to thank Peter
   de Rooij for his patient assistance.  The technical comments of
   Francois Rousseau were valuable contributions.

Authors' Addresses

   Simon Blake-Wilson
   Certicom Corp
   5520 Explorer Drive #400
   Mississauga, ON L4W 5L1

   EMail: sblakewi@certicom.com

   Daniel R. L. Brown
   pCerticom Corp
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   EMail: dbrown@certicom.com

   Paul Lambert

   EMail: plambert@sprintmail.com

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