Internet X.509 Public Key Infrastructure: Additional Algorithm Identifiers for RSASSA-PSS and ECDSA using SHAKEs
draft-ietf-lamps-pkix-shake-05

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LAMPS WG                                                   P. Kampanakis
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                                 Q. Dang
Expires: June 2, 2019                                               NIST
                                                       November 29, 2018

     Internet X.509 Public Key Infrastructure: Additional Algorithm
           Identifiers for RSASSA-PSS and ECDSA using SHAKEs
                     draft-ietf-lamps-pkix-shake-05

Abstract

   Digital signatures are used to sign messages, X.509 certificates and
   CRLs (Certificate Revocation Lists).  This document describes the
   conventions for using the SHAKE function family in Internet X.509
   certificates and CRLs as one-way hash functions with the RSA
   Probabilistic signature and ECDSA signature algorithms.  The
   conventions for the associated subject public keys are also
   described.

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 https://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 June 2, 2019.

Copyright Notice

   Copyright (c) 2018 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

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   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.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Identifiers . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Use in PKIX . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Signatures  . . . . . . . . . . . . . . . . . . . . . . .   5
       5.1.1.  RSASSA-PSS Signatures . . . . . . . . . . . . . . . .   6
       5.1.2.  Deterministic ECDSA Signatures  . . . . . . . . . . .   6
     5.2.  Public Keys . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  ASN.1 module . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Change Log

   [ EDNOTE: Remove this section before publication. ]

   o  draft-ietf-lamps-pkix-shake-05:

      *  Added RFC8174 reference and text.

      *  Explicitly explained why RSASSA-PSS-params are omitted in
         section 5.1.1.

      *  Simplified Public Keys section by removing redundand info from
         RFCs.

   o  draft-ietf-lamps-pkix-shake-04:

      *  Removed paragraph suggesting KMAC to be used in generating k in
         Deterministric ECDSA.  That should be RFC6979-bis.

      *  Removed paragraph from Security Considerations that talks about
         randomness of k because we are using deterministric ECDSA.

      *  Various ASN.1 fixes.

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      *  Text fixes.

   o  draft-ietf-lamps-pkix-shake-03:

      *  Updates based on suggestions and clarifications by Jim.

      *  Added ASN.1.

   o  draft-ietf-lamps-pkix-shake-02:

      *  Significant reorganization of the sections to simplify the
         introduction, the new OIDs and their use in PKIX.

      *  Added new OIDs for RSASSA-PSS that hardcode hash, salt and MGF,
         according the WG consensus.

      *  Updated Public Key section to use the new RSASSA-PSS OIDs and
         clarify the algorithm identifier usage.

      *  Removed the no longer used SHAKE OIDs from section 3.1.

      *  Consolidated subsection for message digest algorithms.

      *  Text fixes.

   o  draft-ietf-lamps-pkix-shake-01:

      *  Changed titles and section names.

      *  Removed DSA after WG discussions.

      *  Updated shake OID names and parameters, added MGF1 section.

      *  Updated RSASSA-PSS section.

      *  Added Public key algorithm OIDs.

      *  Populated Introduction and IANA sections.

   o  draft-ietf-lamps-pkix-shake-00:

      *  Initial version

2.  Introduction

   This document describes cryptographic algorithm identifiers for
   several cryptographic algorithms which use variable length output

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   SHAKE functions introduced in [SHA3] which can be used with the
   Internet X.509 Certificate and CRL profile [RFC5280].

   In the SHA-3 family, two extendable-output functions (SHAKEs),
   SHAKE128 and SHAKE256, are defined.  Four other hash function
   instances, SHA3-224, SHA3-256, SHA3-384, and SHA3-512 are also
   defined but are out of scope for this document.  A SHAKE is a
   variable length hash function.  The output length, in bits, of a
   SHAKE is defined by the d parameter.  The corresponding collision and
   second preimage resistance strengths for SHAKE128 are min(d/2,128)
   and min(d,128) bits respectively.  And, the corresponding collision
   and second preimage resistance strengths for SHAKE256 are
   min(d/2,256) and min(d,256) bits respectively.

   A SHAKE can be used as the message digest function (to hash the
   message to be signed) in RSASSA-PSS and ECDSA and as the hash in the
   mask generating function in RSASSA-PSS.  This specification describes
   the identifiers for SHAKEs to be used in X.509 and their meaning.

3.  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.

4.  Identifiers

   This section defines four new OIDs for RSASSA-PSS and ECDSA when
   SHAKE128 and SHAKE256 are used.  The same algorithm identifiers are
   used for identifying a public key in RSASSA-PSS.

   The new identifiers for RSASSA-PSS signatures using SHAKEs are below.

     id-RSASSA-PSS-SHAKE128  OBJECT IDENTIFIER  ::=  { TBD }

     id-RSASSA-PSS-SHAKE256  OBJECT IDENTIFIER  ::=  { TBD }

     [ EDNOTE: "TBD" will be specified by NIST later. ]

   The new algorithm identifiers of ECDSA signatures using SHAKEs are
   below.

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     id-ecdsa-with-shake128 OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
               country(16) us(840) organization(1) gov(101)
               csor(3) algorithms(4) id-ecdsa-with-shake(3)
               TBD }

     id-ecdsa-with-shake256 OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
               country(16) us(840) organization(1) gov(101)
               csor(3) algorithms(4) id-ecdsa-with-shake(3)
               TBD }

     [ EDNOTE: "TBD" will be specified by NIST later. ]

   The parameters for the four identifiers above MUST be absent.  That
   is, the identifier SHALL be a SEQUENCE of one component, the OID.

   Section 5.1.1 and Section 5.1.2 specify the required output length
   for each use of SHAKE128 or SHAKE256 in RSASSA-PSS and ECDSA.  In
   summary, when hashing messages to be signed, output lengths of
   SHAKE128 and SHAKE256 are 256 and 512 bits respectively.  When the
   SHAKEs are used as mask generation functions RSASSA-PSS, their output
   length is (n - 264) or (n - 520) bits respectively, where n is a RSA
   modulus size in bits.

5.  Use in PKIX

5.1.  Signatures

   Signatures can be placed in a number of different ASN.1 structures.
   The top level structure for an X.509 certificate, to illustrate how
   signatures are frequently encoded with an algorithm identifier and a
   location for the signature, is

      Certificate  ::=  SEQUENCE  {
         tbsCertificate       TBSCertificate,
         signatureAlgorithm   AlgorithmIdentifier,
         signatureValue       BIT STRING  }

   The identifiers defined in Section 4 can be used as the
   AlgorithmIdentifier in the signatureAlgorithm field in the sequence
   Certificate and the signature field in the sequence tbsCertificate in
   X.509 [RFC5280].

   Conforming CA implementations MUST specify the algorithms explicitly
   by using the OIDs specified in Section 4 when encoding RSASSA-PSS or
   ECDSA with SHAKE signatures in certificates and CRLs.  Conforming
   client implementations that process RSASSA-PSS or ECDSA with SHAKE

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   signatures when processing certificates and CRLs MUST recognize the
   corresponding OIDs.  Encoding rules for RSASSA-PSS and ECDSA
   signature values are specified in [RFC4055] and [RFC5480]
   respectively.

5.1.1.  RSASSA-PSS Signatures

   The RSASSA-PSS algorithm is defined in [RFC8017].  When id-RSASSA-
   PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256 specified in Section 4 is
   used, the encoding MUST omit the parameters field.  That is, the
   AlgorithmIdentifier SHALL be a SEQUENCE of one component, id-RSASSA-
   PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256.  [RFC4055] defines RSASSA-
   PSS-params that are used to define the algorithms and inputs to the
   algorithm.  This specification does not use parameters because the
   hash and mask generating algorithsm and trailer and salt are embedded
   in the OID definition.

   The hash algorithm to hash a message being signed and the hash
   algorithm as the mask generation function used in RSASSA-PSS MUST be
   the same, SHAKE128 or SHAKE256 respectively.  The output-length of
   the hash algorithm which hashes the message SHALL be 32 or 64 bytes
   respectively.

   The mask generation function takes an octet string of variable length
   and a desired output length as input, and outputs an octet string of
   the desired length.  In RSASSA-PSS with SHAKES, the SHAKEs MUST be
   used natively as the MGF function, instead of the MGF1 algorithm that
   uses the hash function in multiple iterations as specified in
   Section B.2.1 of [RFC8017].  In other words, the MGF is defined as
   the SHAKE128 or SHAKE256 output of the mgfSeed for id-RSASSA-PSS-
   SHAKE128 and id-RSASSA-PSS-SHAKE256 respectively.  The mgfSeed is the
   seed from which mask is generated, an octet string [RFC8017].  The
   output length is (n - 264)/8 or (n - 520)/8 bytes respectively, where
   n is the RSA modulus in bits.  For example, when RSA modulus n is
   2048, the output length of SHAKE128 or SHAKE256 as the MGF will be
   223 or 191-bits when id-RSASSA-PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256
   is used respectively.

   The RSASSA-PSS saltLength MUST be 32 or 64 bytes respectively.
   Finally, the trailerField MUST be 1, which represents the trailer
   field with hexadecimal value 0xBC [RFC8017].

5.1.2.  Deterministic ECDSA Signatures

   The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined in
   [X9.62].  When the id-ecdsa-with-SHAKE128 or id-ecdsa-with-SHAKE256
   (specified in Section 4) algorithm identifier appears, the respective
   SHAKE function (SHAKE128 or SHAKE256) is used as the hash.  The

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   encoding MUST omit the parameters field.  That is, the
   AlgorithmIdentifier SHALL be a SEQUENCE of one component, the OID id-
   ecdsa-with-SHAKE128 or id-ecdsa-with-SHAKE256.

   For simplicity and compliance with the ECDSA standard specification,
   the output length of the hash function must be explicitly determined.
   The output length, d, for SHAKE128 or SHAKE256 used in ECDSA MUST be
   256 or 512 bits respectively.

   Conforming CA implementations that generate ECDSA with SHAKE
   signatures in certificates or CRLs MUST generate such signatures with
   a deterministicly generated, non-random k in accordance with all the
   requirements specified in [RFC6979].  They MAY also generate such
   signatures in accordance with all other recommendations in [X9.62] or
   [SEC1] if they have a stated policy that requires conformance to
   these standards.  These standards may have not specified SHAKE128 and
   SHAKE256 as hash algorithm options.  However, SHAKE128 and SHAKE256
   with output length being 32 and 64 octets respectively are
   subtitutions for 256 and 512-bit output hash algorithms such as
   SHA256 and SHA512 used in the standards.

5.2.  Public Keys

   Certificates conforming to [RFC5280] can convey a public key for any
   public key algorithm.  The certificate indicates the public key
   algorithm through an algorithm identifier.  This algorithm identifier
   is an OID and optionally associated parameters.

   Conforming CA implementations MUST specify the X.509 public key
   algorithm explicitly by using the OIDs specified in Section 4 when
   encoding RSASSA-PSS or ECDSA with SHAKE public keys in certificates
   and CRLs.  Conforming client implementations that process RSASSA-PSS
   or ECDSA with SHAKE public key when processing certificates and CRLs
   MUST recognize the corresponding OIDs.  The conventions and encoding
   for RSASSA-PSS and ECDSA public keys algorithm identifiers are as
   specified in Section 2.3 of [RFC3279], Section 3.1 of [RFC4055] and
   Section 2.1 of [RFC5480].

   When the RSA private key owner wishes to limit the use of the public
   key exclusively to RSASSA-PSS, the AlgorithmIdentifiers for RSASSA-
   PSS defined in Section 4 can be used as the algorithm field in the
   SubjectPublicKeyInfo sequence [RFC5280].  The identifier parameters,
   as explained in section Section 4, MUST be absent.  The RSASSA-PSS
   algorithm functions and output lengths are the same as defined in
   Section 5.1.1.

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6.  IANA Considerations

   [ EDNOTE: Update here only if there are OID allocations by IANA. ]

   This document has no IANA actions.

7.  Security Considerations

   The SHAKEs are deterministic functions.  Like any other deterministic
   function, executing multiple times with the same input will produce
   the same output.  Therefore, users should not expect unrelated
   outputs (with the same or different output lengths) from running a
   SHAKE function with the same input multiple times.  The shorter of
   any two outputs produced from a SHAKE with the same input is a prefix
   of the longer one.  It is a similar situation as truncating a 512-bit
   output of SHA-512 by taking its 256 left-most bits.  These 256 left-
   most bits are a prefix of the 512-bit output.

   Implementations must protect the signer's private key.  Compromise of
   the signer's private key permits masquerade attacks.

   Implementers should be aware that cryptographic algorithms may become
   weaker with time.  As new cryptanalysis techniques are developed and
   computing power increases, the work factor or time required to break
   a particular cryptographic algorithm may decrease.  Therefore,
   cryptographic algorithm implementations should be modular allowing
   new algorithms to be readily inserted.  That is, implementers should
   be prepared to regularly update the set of algorithms in their
   implementations.

8.  Acknowledgements

   We would like to thank Sean Turner and Jim Schaad for their valuable
   contributions to this document.

9.  References

9.1.  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>.

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   [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,
              DOI 10.17487/RFC4055, June 2005,
              <https://www.rfc-editor.org/info/rfc4055>.

   [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>.

   [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>.

   [RFC8017]  Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
              "PKCS #1: RSA Cryptography Specifications Version 2.2",
              RFC 8017, DOI 10.17487/RFC8017, November 2016,
              <https://www.rfc-editor.org/info/rfc8017>.

   [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>.

   [SHA3]     National Institute of Standards and Technology, "SHA-3
              Standard - Permutation-Based Hash and Extendable-Output
              Functions FIPS PUB 202", August 2015,
              <https://www.nist.gov/publications/sha-3-standard-
              permutation-based-hash-and-extendable-output-functions>.

9.2.  Informative References

   [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>.

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   [SEC1]     Standards for Efficient Cryptography Group, "SEC 1:
              Elliptic Curve Cryptography", May 2009,
              <http://www.secg.org/sec1-v2.pdf>.

   [X9.62]    American National Standard for Financial Services (ANSI),
              "X9.62-2005 Public Key Cryptography for the Financial
              Services Industry: The Elliptic Curve Digital Signature
              Standard (ECDSA)", November 2005.

Appendix A.  ASN.1 module

   This appendix includes the ASN.1 module for SHAKEs in X.509.  This
   module does not come from any existing RFC.

    PKIXAlgsForSHAKE-2018 { iso(1) identified-organization(3) dod(6)
      internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
      id-mod-pkix1-shake-2018(TBD) }

    DEFINITIONS EXPLICIT TAGS ::=

    BEGIN

    -- EXPORTS ALL;

    IMPORTS

    -- FROM [RFC5912]

    PUBLIC-KEY, SIGNATURE-ALGORITHM, DIGEST-ALGORITHM, SMIME-CAPS
    FROM AlgorithmInformation-2009
      { iso(1) identified-organization(3) dod(6) internet(1) security(5)
        mechanisms(5) pkix(7) id-mod(0)
        id-mod-algorithmInformation-02(58) }

    -- FROM [RFC5912]

    RSAPublicKey, rsaEncryption, id-ecPublicKey,
                                 ECPoint, ECDSA-Sig-Value
    FROM PKIXAlgs-2009 { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
         id-mod-pkix1-algorithms2008-02(56) }

    --
    -- Message Digest Algorithms (mda-)
    --
    HashAlgs DIGEST-ALGORITHM ::= {
     ...

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     -- This expands MessageAuthAlgs from [RFC5912]
     mda-shake128   |
     mda-shake256,
     ...
    }

    --
    -- One-Way Hash Functions
    -- SHAKE128
    mda-shake128 DIGEST-ALGORITHM ::= {
      IDENTIFIER id-shake128  -- with output length 32 bytes.
    }
    id-shake128 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16)
                                        us(840) organization(1) gov(101)
                                        csor(3) nistAlgorithm(4)
                                        hashAlgs(2) 11 }

    -- SHAKE-256
    mda-shake256 DIGEST-ALGORITHM ::= {
      IDENTIFIER id-shake256  -- with output length 64 bytes.
    }
    id-shake256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16)
                                        us(840) organization(1) gov(101)
                                        csor(3) nistAlgorithm(4)
                                        hashAlgs(2) 12 }

    --
    -- Public Key (pk-) Algorithms
    --
    PublicKeys PUBLIC-KEY ::= {
      ...
      pk-rsaSSA-PSS-SHAKE128 |
      pk-rsaSSA-PSS-SHAKE256,
          ...
    }

    -- From [RFC5912] - Here so it compiles.
    pk-rsa PUBLIC-KEY ::= {
     IDENTIFIER rsaEncryption
     KEY RSAPublicKey
     PARAMS TYPE NULL ARE absent
     -- Private key format not in this module --
     CERT-KEY-USAGE {digitalSignature, nonRepudiation,
     keyEncipherment, dataEncipherment, keyCertSign, cRLSign}
    }

    -- The hashAlgorithm is mda-shake128
    -- The maskGenAlgorithm is id-shake128

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    -- Mask Gen Algorithm is SHAKE128 with output length
    -- (n - 264)/8, where n is the RSA modulus in bits.
    -- the saltLength is 32
    -- the trailerField is 1
    pk-rsaSSA-PSS-SHAKE128 PUBLIC-KEY ::= {
        IDENTIFIER id-RSASSA-PSS-SHAKE128
        KEY RSAPublicKey
        PARAMS TYPE NULL ARE absent
         -- Private key format not in this module --
        CERT-KEY-USAGE { nonRepudiation, digitalSignature,
                             keyCertSign, cRLSign }
    }

    -- The hashAlgorithm is mda-shake256
    -- The maskGenAlgorithm is id-shake256
    -- Mask Gen Algorithm is SHAKE256 with output length
    -- (n - 520)/8, where n is the RSA modulus in bits.
    -- the saltLength is 64
    -- the trailerField is 1
    pk-rsaSSA-PSS-SHAKE256 PUBLIC-KEY ::= {
        IDENTIFIER id-RSASSA-PSS-SHAKE256
        KEY RSAPublicKey
        PARAMS TYPE NULL ARE absent
         -- Private key format not in this module --
        CERT-KEY-USAGE { nonRepudiation, digitalSignature,
                             keyCertSign, cRLSign }
    }

    pk-ec PUBLIC-KEY ::= {
      IDENTIFIER id-ecPublicKey
      KEY ECPoint
      PARAMS TYPE ECParameters ARE required
      -- Private key format not in this module --
      CERT-KEY-USAGE { digitalSignature, nonRepudiation, keyAgreement,
                       keyCertSign, cRLSign }
    }
    ECParameters ::= CHOICE {
     namedCurve      CURVE.&id({NamedCurve})
     -- implicitCurve   NULL
       -- implicitCurve MUST NOT be used in PKIX
     -- specifiedCurve  SpecifiedCurve
       -- specifiedCurve MUST NOT be used in PKIX
       -- Details for specifiedCurve can be found in [X9.62]
       -- Any future additions to this CHOICE should be coordinated
       -- with ANSI X.9.
    }

    --

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    -- Signature Algorithms (sa-)
    --
    SignatureAlgs SIGNATURE-ALGORITHM ::= {
      ...
      -- This expands SignatureAlgorithms from [RFC5912]
      sa-rsassapssWithSHAKE128 |
      sa-rsassapssWithSHAKE256,
      ...
      sa-ecdsaWithSHAKE128 |
      sa-ecdsaWithSHAKE256,
          ...
    }

    --
    -- SMIME Capabilities (sa-)
    --
    SMimeCaps SMIME-CAPS ::= {
      ...
      -- The expands SMimeCaps from [RFC5912]
      sa-rsassapssWithSHAKE128.&smimeCaps |
      sa-rsassapssWithSHAKE256.&smimeCaps,
      sa-ecdsaWithSHAKE128.&smimeCaps |
      sa-ecdsaWithSHAKE256.&smimeCaps,
          ...
      }

    -- RSASSA-PSS with SHAKE128
    sa-rsassapssWithSHAKE128 SIGNATURE-ALGORITHM ::= {
       IDENTIFIER id-RSASSA-PSS-SHAKE128
       PARAMS TYPE NULL ARE absent
          -- The hashAlgorithm is mda-shake128
          -- The maskGenAlgorithm is id-shake128
          -- Mask Gen Algorithm is SHAKE128 with output length
          -- (n - 264)/8, where n is the RSA modulus in bits.
          -- the saltLength is 32
          -- the trailerField is 1
           HASHES mda-shake128
       PUBLIC-KEYS { pk-rsa | pk-rsaSSA-PSS-SHAKE128 }
       SMIME-CAPS { IDENTIFIED BY id-RSASSA-PSS-SHAKE128 }
    }
    id-RSASSA-PSS-SHAKE128  OBJECT IDENTIFIER  ::=  { TBD }

    -- RSASSA-PSS with SHAKE256
    sa-rsassapssWithSHAKE256 SIGNATURE-ALGORITHM ::= {
       IDENTIFIER id-RSASSA-PSS-SHAKE256
       PARAMS TYPE NULL ARE absent
          -- The hashAlgorithm is mda-shake256
          -- The maskGenAlgorithm is id-shake256

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          -- Mask Gen Algorithm is SHAKE256 with output length
          -- (n - 520)/8, where n is the RSA modulus in bits.
          -- the saltLength is 64
          -- the trailerField is 1
           HASHES mda-shake256
       PUBLIC-KEYS { pk-rsa | pk-rsaSSA-PSS-SHAKE256 }
       SMIME-CAPS { IDENTIFIED BY id-RSASSA-PSS-SHAKE256 }
    }
    id-RSASSA-PSS-SHAKE256  OBJECT IDENTIFIER  ::=  { TBD }

    -- Determinstic ECDSA with SHAKE128
    sa-ecdsaWithSHAKE128 SIGNATURE-ALGORITHM ::= {
       IDENTIFIER id-ecdsa-with-shake128
       VALUE ECDSA-Sig-Value
       PARAMS TYPE NULL ARE absent
       HASHES { mda-shake128 }
       PUBLIC-KEYS { pk-ec }
       SMIME-CAPS { IDENTIFIED BY id-ecdsa-with-shake128 }
    }
    id-ecdsa-with-shake128 ::= { joint-iso-itu-t(2) country(16)
                                 us(840) organization(1) gov(101)
                                 csor(3) nistAlgorithm(4)
                                 sigAlgs(3) TBD }

    -- Determinstic ECDSA with SHAKE256
    sa-ecdsaWithSHAKE256 SIGNATURE-ALGORITHM ::= {
       IDENTIFIER id-ecdsa-with-shake256
       VALUE ECDSA-Sig-Value
       PARAMS TYPE NULL ARE absent
       HASHES { mda-shake256 }
       PUBLIC-KEYS { pk-ec }
       SMIME-CAPS { IDENTIFIED BY id-ecdsa-with-shake256 }
    }
    id-ecdsa-with-shake256 ::= { joint-iso-itu-t(2) country(16)
                                 us(840) organization(1) gov(101)
                                 csor(3) nistAlgorithm(4)
                                 sigAlgs(3) TBD }

    END

Authors' Addresses

   Panos Kampanakis
   Cisco Systems

   Email: pkampana@cisco.com

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   Quynh Dang
   NIST
   100 Bureau Drive, Stop 8930
   Gaithersburg, MD  20899-8930
   USA

   Email: quynh.dang@nist.gov

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