Internet DRAFT - draft-schaad-cose-alg

draft-schaad-cose-alg







COSE Working Group                                             J. Schaad
Internet-Draft                                            August Cellars
Intended status: Informational                            March 21, 2016
Expires: September 22, 2016


           CBOR Encoded Message Syntax: Additional Algorithms
                        draft-schaad-cose-alg-01

Abstract

   This document defines the identifiers and usage for a set of
   additional cryptographic algorithms in the CBOR Encoded Message
   (COSE) Syntax.

   The algorithms setup in this docment are: RSA-PSS, RSA-OAEP, ....
   !!TBD!!

Contributing to this document

   The source for this draft is being maintained in GitHub.  Suggested
   changes should be submitted as pull requests at <https://github.com/
   cose-wg/cose-algs>.  Instructions are on that page as well.
   Editorial changes can be managed in GitHub, but any substantial
   issues need to be discussed on the COSE mailing list.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 22, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   3
     1.2.  Document Terminology  . . . . . . . . . . . . . . . . . .   3
   2.  Signature Algorithms  . . . . . . . . . . . . . . . . . . . .   3
     2.1.  RSASSA-PSS  . . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.1.  Security Considerations . . . . . . . . . . . . . . .   4
     2.2.  Edwards-curve Digital Signature Algorithms (EdDSA)  . . .   4
   3.  Message Authentication (MAC) Algorithms . . . . . . . . . . .   6
   4.  Content Encryption Algorithms . . . . . . . . . . . . . . . .   6
   5.  Key Derivation Functions (KDF)  . . . . . . . . . . . . . . .   6
   6.  Recipient Algorithms  . . . . . . . . . . . . . . . . . . . .   6
     6.1.  RSAES-OAEP  . . . . . . . . . . . . . . . . . . . . . . .   6
       6.1.1.  Security Considerations for RSAES-OAEP  . . . . . . .   6
     6.2.  ECDH  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  Keys  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Octet Key Pair  . . . . . . . . . . . . . . . . . . . . .   8
     7.2.  RSA Keys  . . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  COSE Header Parameter Registry  . . . . . . . . . . . . .  10
     8.2.  COSE Header Algorithm Label Table . . . . . . . . . . . .  11
     8.3.  COSE Algorithm Registry . . . . . . . . . . . . . . . . .  11
     8.4.  COSE Key Common Parameter Registry  . . . . . . . . . . .  11
     8.5.  COSE Key Type Parameter Registry  . . . . . . . . . . . .  11
     8.6.  COSE Elliptic Curve Registry  . . . . . . . . . . . . . .  11
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     10.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Document Updates . . . . . . . . . . . . . . . . . .  16
     A.1.  Version -00 . . . . . . . . . . . . . . . . . . . . . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  17








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1.  Introduction

   In the process of writing RFCXXXX [I-D.ietf-cose-msg] several
   algorithms were removed from that document to be addressed at a later
   date.  This document deals with a large set of the cryptographic
   algorithms which were removed at that time.

   This document provides the necessary conventions needed to use the
   algorithms defined in this document.  This document additionally
   provides the necessary registration in the appropriate IANA registry
   tables.

1.1.  Requirements 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
   [RFC2119].

   When the words appear in lower case, their natural language meaning
   is used.

1.2.  Document Terminology

   In this document we use the following terminology: [CREF1]

2.  Signature Algorithms

   This document defines two new signature algorithms: RSA-PSS and
   Edwards Curve Digital Signature Algorithm (EdDSA).  Both of these
   signature algorithms are Signature Scheme with Appendix algorithms.
   (For a discussion on the difference between signature scheme with
   appendix and signature scheme with message recovery algorithms, see
   [I-D.ietf-cose-msg].)

2.1.  RSASSA-PSS

   The RSASSA-PSS signature algorithm is defined in [RFC3447].

   The RSASSA-PSS signature algorithm is parametized with a hash
   function (h), a mask generation function (mgf) and a salt length
   (sLen).  For this specification, the mask generation function is
   fixed to be MGF1 as defined in [RFC3447].  It has been recommended
   that the same hash function be used for hashing the data as well as
   in the mask generation function, for this specification we following
   this recommendation.  The salt length is the same length as the hash
   function output.




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   Implementations need to check that the key type is 'RSA' when
   creating or verifying a signature.

   The algorithms defined in this document can be found in Table 1.

     +-------+-------+---------+-------------+-----------------------+
     | name  | value | hash    | salt length | description           |
     +-------+-------+---------+-------------+-----------------------+
     | PS256 | TBD1  | SHA-256 | 32          | RSASSA-PSS w/ SHA-256 |
     |       |       |         |             |                       |
     | PS384 | TBD2  | SHA-384 | 48          | RSASSA-PSS w/ SHA-384 |
     |       |       |         |             |                       |
     | PS512 | TBD3  | SHA-512 | 64          | RSASSA-PSS w/ SHA-512 |
     +-------+-------+---------+-------------+-----------------------+

                   Table 1: RSASSA-PSS Algorithm Values

2.1.1.  Security Considerations

   In addition to needing to worry about keys that are too small to
   provide the required security, there are issues with keys that are
   too large.  Denial of service attacks have been mounted with overly
   large keys.  This has the potential to consume resources with
   potentially bad keys.  There are two reasonable ways to address this
   attack.  First, a key should not be used for a cryptographic
   operation until it has been matched back to an authorized user.  This
   approach means that no cryptography would be done except for
   authorized users.  Second, applications can impose maximum as well as
   minimum length requirements on keys.  This limits the resources
   consumed even if the matching is not performed until the cryptography
   has been done.

   There is a theoretical hash substitution attack that can be mounted
   against RSASSA-PSS.  However, the requirement that the same hash
   function be used consistently for all operations is an effective
   mitigation against it.  Unlike ECDSA, hash functions are not
   truncated so that the full hash value is always signed.  The internal
   padding structure of RSASSA-PSS means that one needs to have multiple
   collisions between the two hash functions in order to be successful
   in producing a forgery based on changing the hash function.  This is
   highly unlikely.

2.2.  Edwards-curve Digital Signature Algorithms (EdDSA)

   [I-D.irtf-cfrg-eddsa] describes the elliptic curve signature scheme
   Edwards-curve Digital Signature Algorithm (EdDSA).  In that document,
   the signature algorithm is instantiated using parameters for
   edwards25519 and edwards448 curves.  The document additionally



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   describes two variants of the EdDSA algorithm: Pure EdDSA, where no
   hash function is applied to the content before signing and, HashEdDSA
   where a hash function is applied to the content before signing and
   the result of that hash function is signed.  For use with COSE, on
   the pure EdDSA version is used.  This is because it is not expected
   that extremely large contents are going to be needed and, based on
   the arrangement of the message structure, the entire message is going
   to need to be held in memory in order to create or verify a
   signature.  Thus, the use of an incremental update process would not
   be useful.  Applications can provide the same features by defining
   the content of the message as a hash value and transporting the COSE
   message and the content as separate items.

   The algorithms defined in this document can be found in Table 2.  A
   single signature algorithm is defined which can be used for multiple
   curves.

                      +-------+-------+-------------+
                      | name  | value | description |
                      +-------+-------+-------------+
                      | EdDSA | *     | EdDSA       |
                      +-------+-------+-------------+

                      Table 2: EdDSA Algorithm Values

   [I-D.irtf-cfrg-eddsa] describes the method of encoding the signature
   value.

   When using a COSE key for this algorithm the following checks are
   made:

   o  The 'kty' field MUST be present and it MUST be 'OKP'.

   o  The 'crv' field MUST be present, and it MUST be a curve defined
      for this signature algorithm.

   o  If the 'alg' field is present, it MUST match 'EdDSA'.

   o  If the 'key_ops' field is present, it MUST include 'sign' when
      creating an EdDSA signature.

   o  If the 'key_ops' field is present, it MUST include 'verify' when
      verifying an EdDSA signature.








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3.  Message Authentication (MAC) Algorithms

   This document defines no new Message Authentication Code algorithms.

4.  Content Encryption Algorithms

   This document defines no new content inception algorithms.

5.  Key Derivation Functions (KDF)

   This document defines new new key derivation functions.

6.  Recipient Algorithms

6.1.  RSAES-OAEP

   RSAES-OAEP is an asymmetric key encryption algorithm.  The defintion
   of RSAEA-OAEP can be find in Section 7.1 of [RFC3447].  The algorithm
   is parameterized using a masking generation function (mgf), a hash
   function (h) and encoding parameters (P).  For the algorithm
   identifiers defined in this section:

   o  mgf is always set to MFG1 from [RFC3447] and uses the same hash
      function as h.

   o  P is always set to the empty octet string.

   Table 3 summarizes the rest of the values.

    +----------------------+-------+---------+-----------------------+
    | name                 | value | hash    | description           |
    +----------------------+-------+---------+-----------------------+
    | RSAES-OAEP w/SHA-256 | -25   | SHA-256 | RSAES OAEP w/ SHA-256 |
    |                      |       |         |                       |
    | RSAES-OAEP w/SHA-512 | -26   | SHA-512 | RSAES OAEP w/ SHA-512 |
    +----------------------+-------+---------+-----------------------+

                   Table 3: RSAES-OAEP Algorithm Values

   The key type MUST be 'RSA'.

6.1.1.  Security Considerations for RSAES-OAEP

   A key size of 2048 bits or larger MUST be used with these algorithms.
   This key size corresponds roughly to the same strength as provided by
   a 128-bit symmetric encryption algorithm.





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   It is highly recommended that checks on the key length be done before
   starting a decryption operation.  One potential denial of service
   operation is to provide encrypted objects using either abnormally
   long or oddly sized RSA modulus values.  Implementations SHOULD be
   able to encrypt and decrypt with modulus between 2048 and 16K bits in
   length.  Applications can impose additional restrictions on the
   length of the modulus.

6.2.  ECDH

   The algorithm ECDH is defined for use in COSE in [I-D.ietf-cose-msg].
   In this document the algorithm is extended to be used with the two
   curves defined in [I-D.irtf-cfrg-curves].

   The following updates [I-D.ietf-cose-msg] sections 12.4.1 and 12.5.1.

   o  OLD: The 'kty' field MUST be present and it MUST be 'EC2'.

   o  NEW: The 'kty' field MUST be present and it MUST be 'EC2' or
      'OKP'.

   All the rest of the checks remain the same.

7.  Keys

   The COSE_Key object defines a way to hold a single key object, it is
   still required that the members of individual key types be defined.
   This section of the document is where we define an initial set of
   members for specific key types.

   For each of the key types, we define both public and private members.
   The public members are what is transmitted to others for their usage.
   We define private members mainly for the purpose of archival of keys
   by individuals.  However, there are some circumstances where private
   keys may be distributed by various entities in a protocol.  Examples
   include: Entities which have poor random number generation.
   Centralized key creation for multi-cast type operations.  Protocols
   where a shared secret is used as a bearer token for authorization
   purposes.

   Key types are identified by the 'kty' member of the COSE_Key object.
   In this document we define four values for the member.









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                    +------+--------+----------------+
                    | name | value  | description    |
                    +------+--------+----------------+
                    | OPK  | TBDXX  | Octet Key Pair |
                    |      |        |                |
                    | RSA  | TBDXX1 | RSA Keys       |
                    +------+--------+----------------+

                         Table 4: Key Type Values

7.1.  Octet Key Pair

   A new key type is defined for Octet Key Pairs (OKP).  Do not assume
   that keys using this type are elliptic curves.  This key type could
   be used for other curve types (for example mathematics based on
   hyper-elliptic surfaces).

   The key parameters defined in this section are summarized in Table 5.
   The members that are defined for this key type are:

   crv  contains an identifier of the curve to be used with the key.
      [CREF2] The curves defined in this document for this key type can
      be found in Table 6.  Other curves may be registered in the future
      and private curves can be used as well.

   x  contains the x coordinate for the EC point.  The octet string
      represents a little-endian encoding of x.

   d  contains the private key.

   For public keys, it is REQUIRED that 'crv' and 'x' be present in the
   structure.  For private keys, it is REQUIRED that 'crv' and 'd' be
   present in the structure.  For private keys, it is RECOMMENDED that
   'x' also be present, but it can be recomputed from the required
   elements and omitting it saves on space.
















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   +------+-------+-------+--------+-----------------------------------+
   | name | key   | value | type   | description                       |
   |      | type  |       |        |                                   |
   +------+-------+-------+--------+-----------------------------------+
   | crv  | 1     | -1    | int /  | EC Curve identifier - Taken from  |
   |      |       |       | tstr   | the COSE General Registry         |
   |      |       |       |        |                                   |
   | x    | 1     | -2    | bstr   | X Coordinate                      |
   |      |       |       |        |                                   |
   | d    | 1     | -4    | bstr   | Private key                       |
   +------+-------+-------+--------+-----------------------------------+

                        Table 5: EC Key Parameters

             +------------+----------+--------+-------------+
             | name       | key type | value  | description |
             +------------+----------+--------+-------------+
             | Curve25519 | EC1      | TBDYY1 | Curve 25519 |
             |            |          |        |             |
             | Curve448   | EC1      | TBDYY2 | Curve 448   |
             +------------+----------+--------+-------------+

                            Table 6: EC Curves

7.2.  RSA Keys

   This document defines a key structure for both the public and private
   halves of RSA keys.  Together, an RSA public key and an RSA private
   key form an RSA key pair.  [CREF3]

   The document also provides support for the so-called "multi-prime"
   RSA where the modulus may have more than two prime factors.  The
   benefit of multi-prime RSA is lower computational cost for the
   decryption and signature primitives.  For a discussion on how multi-
   prime affects the security of RSA crypto-systems, the reader is
   referred to [MultiPrimeRSA].

   This document follows the naming convention of [RFC3447] for the
   naming of the fields of an RSA public or private key.  The table
   Table 7 provides a summary of the label values and the types
   associated with each of those labels.  The requirements for fields
   for RSA keys are as follows:

   o  For all keys, 'kty' MUST be present and MUST have a value of 3.

   o  For public keys, the fields 'n' and 'e' MUST be present.  All
      other fields defined in Table 7 MUST be absent.




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   o  For private keys with two primes, the fields 'other', 'r_i', 'd_i'
      and 't_i' MUST be absent, all other fields MUST be present.

   o  For private keys with more than two primes, all fields MUST be
      present.  For the third to nth primes, each of the primes is
      represented as a map containing the fields 'r_i', 'd_i' and 't_i'.
      The field 'other' is an array of those maps.

   +-------+----------+-------+-------+--------------------------------+
   | name  | key type | value | type  | description                    |
   +-------+----------+-------+-------+--------------------------------+
   | n     | 3        | -1    | bstr  | Modulus Parameter              |
   |       |          |       |       |                                |
   | e     | 3        | -2    | int   | Exponent Parameter             |
   |       |          |       |       |                                |
   | d     | 3        | -3    | bstr  | Private Exponent Parameter     |
   |       |          |       |       |                                |
   | p     | 3        | -4    | bstr  | First Prime Factor             |
   |       |          |       |       |                                |
   | q     | 3        | -5    | bstr  | Second Prime Factor            |
   |       |          |       |       |                                |
   | dP    | 3        | -6    | bstr  | First Factor CRT Exponent      |
   |       |          |       |       |                                |
   | dQ    | 3        | -7    | bstr  | Second Factor CRT Exponent     |
   |       |          |       |       |                                |
   | qInv  | 3        | -8    | bstr  | First CRT Coefficient          |
   |       |          |       |       |                                |
   | other | 3        | -9    | array | Other Primes Info              |
   |       |          |       |       |                                |
   | r_i   | 3        | -10   | bstr  | i-th factor, Prime Factor      |
   |       |          |       |       |                                |
   | d_i   | 3        | -11   | bstr  | i-th factor, Factor CRT        |
   |       |          |       |       | Exponent                       |
   |       |          |       |       |                                |
   | t_i   | 3        | -12   | bstr  | i-th factor, Factor CRT        |
   |       |          |       |       | Coefficient                    |
   +-------+----------+-------+-------+--------------------------------+

                        Table 7: RSA Key Parameters

8.  IANA Considerations

8.1.  COSE Header Parameter Registry

   There are currently no registration requests here






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8.2.  COSE Header Algorithm Label Table

   TBD

8.3.  COSE Algorithm Registry

   TBD

8.4.  COSE Key Common Parameter Registry

   There are currently no registration tasks inthis section.

8.5.  COSE Key Type Parameter Registry

   It is requested that IANA create a new registry "COSE Key Type
   Parameters".

   The columns of the table are:

   key type  This field contains a descriptive string of a key type.
      This should be a value that is in the COSE General Values table
      and is placed in the 'kty' field of a COSE Key structure.

   name  This is a descriptive name that enables easier reference to the
      item.  It is not used in the encoding.

   label  The label is to be unique for every value of key type.  The
      range of values is from -256 to -1.  Labels are expected to be
      reused for different keys.

   CBOR type  This field contains the CBOR type for the field

   description  This field contains a brief description for the field

   specification  This contains a pointer to the public specification
      for the field if one exists

   This registry will be initially populated by the values in Table 5,
   and Table 7.  The specification column for all of these entries will
   be this document.

8.6.  COSE Elliptic Curve Registry

   It is requested that IANA create a new registry "COSE Elliptic Curve
   Parameters".

   The columns of the table are:




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   name  This is a descriptive name that enables easier reference to the
      item.  It is not used in the encoding.

   value  This is the value used to identify the curve.  These values
      MUST be unique.  The integer values from -256 to 255 are
      designated as Standards Track Document Required.  The the integer
      values from 256 to 65535 and -65536 to -257 are designated as
      Specification Required.  Integer values over 65535 are designated
      as first come first serve.  Integer values less than -65536 are
      marked as private use.

   key type  This designates the key type(s) that can be used with this
      curve.

   description  This field contains a brief description of the curve.

   specification  This contains a pointer to the public specification
      for the curve if one exists.

   This registry will be initially populated by the values in Table 4.
   The specification column for all of these entries will be this
   document.

9.  Security Considerations

   There are security considerations:

   1.  Protect private keys

   2.  MAC messages with more than one recipient means one cannot figure
       out who sent the message

   3.  Use of direct key with other recipient structures hands the key
       to other recipients.

   4.  Use of direct ECDH direct encryption is easy for people to leak
       information on if there are other recipients in the message.

   5.  Considerations about protected vs unprotected header fields.

   6.  Need to verify that: 1) the kty field of the key matches the key
       and algorithm being used.  2) that the kty field needs to be
       included in the trust decision as well as the other key fields.
       3) that the algorithm be included in the trust decision.







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10.  References

10.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <http://www.rfc-editor.org/info/rfc7049>.

10.2.  Informative References

   [AES-GCM]  Dworkin, M., "NIST Special Publication 800-38D:
              Recommendation for Block Cipher Modes of Operation:
              Galois/Counter Mode (GCM) and GMAC.", Nov 2007.

   [DSS]      U.S. National Institute of Standards and Technology,
              "Digital Signature Standard (DSS)", July 2013.

   [I-D.greevenbosch-appsawg-cbor-cddl]
              Vigano, C. and H. Birkholz, "CBOR data definition language
              (CDDL): a notational convention to express CBOR data
              structures", draft-greevenbosch-appsawg-cbor-cddl-07 (work
              in progress), October 2015.

   [I-D.ietf-cose-msg]
              Schaad, J., "CBOR Encoded Message Syntax", draft-ietf-
              cose-msg-10 (work in progress), February 2016.

   [I-D.irtf-cfrg-curves]
              Langley, A. and M. Hamburg, "Elliptic Curves for
              Security", draft-irtf-cfrg-curves-11 (work in progress),
              October 2015.

   [I-D.irtf-cfrg-eddsa]
              Josefsson, S. and I. Liusvaara, "Edwards-curve Digital
              Signature Algorithm (EdDSA)", draft-irtf-cfrg-eddsa-05
              (work in progress), March 2016.

   [MAC]      NiST, N., "FIPS PUB 113: Computer Data Authentication",
              May 1985.

   [MultiPrimeRSA]
              Hinek, M. and D. Cheriton, "On the Security of Multi-prime
              RSA", June 2006.



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   [PVSig]    Brown, D. and D. Johnson, "Formal Security Proofs for a
              Signature Scheme with Partial Message Recover", February
              2000.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997,
              <http://www.rfc-editor.org/info/rfc2104>.

   [RFC2633]  Ramsdell, B., Ed., "S/MIME Version 3 Message
              Specification", RFC 2633, DOI 10.17487/RFC2633, June 1999,
              <http://www.rfc-editor.org/info/rfc2633>.

   [RFC2898]  Kaliski, B., "PKCS #5: Password-Based Cryptography
              Specification Version 2.0", RFC 2898,
              DOI 10.17487/RFC2898, September 2000,
              <http://www.rfc-editor.org/info/rfc2898>.

   [RFC3394]  Schaad, J. and R. Housley, "Advanced Encryption Standard
              (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
              September 2002, <http://www.rfc-editor.org/info/rfc3394>.

   [RFC3447]  Jonsson, J. and B. Kaliski, "Public-Key Cryptography
              Standards (PKCS) #1: RSA Cryptography Specifications
              Version 2.1", RFC 3447, DOI 10.17487/RFC3447, February
              2003, <http://www.rfc-editor.org/info/rfc3447>.

   [RFC3610]  Whiting, D., Housley, R., and N. Ferguson, "Counter with
              CBC-MAC (CCM)", RFC 3610, DOI 10.17487/RFC3610, September
              2003, <http://www.rfc-editor.org/info/rfc3610>.

   [RFC4231]  Nystrom, M., "Identifiers and Test Vectors for HMAC-SHA-
              224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",
              RFC 4231, DOI 10.17487/RFC4231, December 2005,
              <http://www.rfc-editor.org/info/rfc4231>.

   [RFC4262]  Santesson, S., "X.509 Certificate Extension for Secure/
              Multipurpose Internet Mail Extensions (S/MIME)
              Capabilities", RFC 4262, DOI 10.17487/RFC4262, December
              2005, <http://www.rfc-editor.org/info/rfc4262>.

   [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,
              <http://www.rfc-editor.org/info/rfc5480>.






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   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <http://www.rfc-editor.org/info/rfc5652>.

   [RFC5751]  Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
              Mail Extensions (S/MIME) Version 3.2 Message
              Specification", RFC 5751, DOI 10.17487/RFC5751, January
              2010, <http://www.rfc-editor.org/info/rfc5751>.

   [RFC5752]  Turner, S. and J. Schaad, "Multiple Signatures in
              Cryptographic Message Syntax (CMS)", RFC 5752,
              DOI 10.17487/RFC5752, January 2010,
              <http://www.rfc-editor.org/info/rfc5752>.

   [RFC5869]  Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
              Key Derivation Function (HKDF)", RFC 5869,
              DOI 10.17487/RFC5869, May 2010,
              <http://www.rfc-editor.org/info/rfc5869>.

   [RFC5990]  Randall, J., Kaliski, B., Brainard, J., and S. Turner,
              "Use of the RSA-KEM Key Transport Algorithm in the
              Cryptographic Message Syntax (CMS)", RFC 5990,
              DOI 10.17487/RFC5990, September 2010,
              <http://www.rfc-editor.org/info/rfc5990>.

   [RFC6090]  McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
              Curve Cryptography Algorithms", RFC 6090,
              DOI 10.17487/RFC6090, February 2011,
              <http://www.rfc-editor.org/info/rfc6090>.

   [RFC6151]  Turner, S. and L. Chen, "Updated Security Considerations
              for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
              RFC 6151, DOI 10.17487/RFC6151, March 2011,
              <http://www.rfc-editor.org/info/rfc6151>.

   [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, <http://www.rfc-editor.org/info/rfc6979>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <http://www.rfc-editor.org/info/rfc7159>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,
              <http://www.rfc-editor.org/info/rfc7252>.



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   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <http://www.rfc-editor.org/info/rfc7515>.

   [RFC7516]  Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              RFC 7516, DOI 10.17487/RFC7516, May 2015,
              <http://www.rfc-editor.org/info/rfc7516>.

   [RFC7517]  Jones, M., "JSON Web Key (JWK)", RFC 7517,
              DOI 10.17487/RFC7517, May 2015,
              <http://www.rfc-editor.org/info/rfc7517>.

   [RFC7518]  Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
              DOI 10.17487/RFC7518, May 2015,
              <http://www.rfc-editor.org/info/rfc7518>.

   [RFC7539]  Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF
              Protocols", RFC 7539, DOI 10.17487/RFC7539, May 2015,
              <http://www.rfc-editor.org/info/rfc7539>.

   [SEC1]     Standards for Efficient Cryptography Group, "SEC 1:
              Elliptic Curve Cryptography", May 2009.

   [SP800-56A]
              Barker, E., Chen, L., Roginsky, A., and M. Smid, "NIST
              Special Publication 800-56A: Recommendation for Pair-Wise
              Key Establishment Schemes Using Discrete Logarithm
              Cryptography", May 2013.

Appendix A.  Document Updates

A.1.  Version -00

   o  TBD

Editorial Comments

[CREF1] JLS: I have not gone through the document to determine what
        needs to be here yet.  We mostly want to grab terms which are
        used in unusual ways or are not generally understood.

[CREF2] JLS: Is is the same registry for both OKP and EC2?

[CREF3] JLS: Looking at the CBOR specification, the bstr that we are
        looking in our table below should most likely be specified as
        big numbers rather than as binary strings.  This means that we
        would use the tag 6.2 instead.  From my reading of the
        specification, there is no difference in the encoded size of the



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        resulting output.  The specification of bignum does explicitly
        allow for integers encoded with leading zeros.

Author's Address

   Jim Schaad
   August Cellars

   Email: ietf@augustcellars.com










































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