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Versions: (draft-housley-suit-cose-hash-sig) 00 01 02 03 04 05 06 07 08 09

Network Working Group                                         R. Housley
Internet-Draft                                            Vigil Security
Intended status: Standards Track                        October 28, 2019
Expires: April 30, 2020


   Use of the HSS/LMS Hash-based Signature Algorithm with CBOR Object
                     Signing and Encryption (COSE)
                      draft-ietf-cose-hash-sig-05

Abstract

   This document specifies the conventions for using the Hierarchical
   Signature System (HSS) / Leighton-Micali Signature (LMS) hash-based
   signature algorithm with the CBOR Object Signing and Encryption
   (COSE) syntax.  The HSS/LMS algorithm is one form of hash-based
   digital signature; it is described in RFC 8554.

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
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   This Internet-Draft will expire on April 30, 2020.

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
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  LMS Digital Signature Algorithm Overview  . . . . . . . . . .   3
     2.1.  Hierarchical Signature System (HSS) . . . . . . . . . . .   4
     2.2.  Leighton-Micali Signature (LMS) . . . . . . . . . . . . .   5
     2.3.  Leighton-Micali One-time Signature Algorithm (LM-OTS) . .   6
   3.  Hash-based Signature Algorithm Identifiers  . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
     4.1.  Implementation Security Considerations  . . . . . . . . .   7
   5.  Operational Considerations  . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  COSE Algorithms Registry Entry  . . . . . . . . . . . . .   9
     6.2.  COSE Key Types Registry Entry . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  11
     A.1.  Example COSE Full Message Signature . . . . . . . . . . .  11
     A.2.  Example COSE_Sign0 Message  . . . . . . . . . . . . . . .  16
   Appendix B.  Acknowledgements . . . . . . . . . . . . . . . . . .  21
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   This document specifies the conventions for using the Hierarchical
   Signature System (HSS) / Leighton-Micali Signature (LMS) hash-based
   signature algorithm with with the CBOR Object Signing and Encryption
   (COSE) [RFC8152] syntax.  The LMS system provides a one-time digital
   signature that is a variant of Merkle Tree Signatures (MTS).  The HSS
   is built on top of the LMS system to efficiently scale for a larger
   numbers of signatures.  The HSS/LMS algorithm is one form of hash-
   based digital signature, and it is described in [HASHSIG].  The HSS/
   LMS signature algorithm can only be used for a fixed number of
   signing operations.  The number of signing operations depends upon
   the size of the tree.  The HSS/LMS signature algorithm uses small
   public keys, and it has low computational cost; however, the
   signatures are quite large.  The HSS/LMS private key can be very
   small when the signer is willing to perform additional computation at
   signing time; alternatively, the private key can consume additional
   memory and provide a faster signing time.  The HSS/LMS signatures
   [HASHSIG] are currently defined to use exclusively SHA-256 [SHS].




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1.1.  Motivation

   Recent advances in cryptanalysis [BH2013] and progress in the
   development of quantum computers [NAS2019] pose a threat to widely
   deployed digital signature algorithms.  As a result, there is a need
   to prepare for a day that cryptosystems such as RSA and DSA that
   depend on discrete logarithm and factoring cannot be depended upon.

   If large-scale quantum computers are ever built, these computers will
   be able to break many of the public-key cryptosystems currently in
   use.  A post-quantum cryptosystem [PQC] is a system that is secure
   against quantum computers that have more than a trivial number of
   quantum bits (qubits).  It is open to conjecture when it will be
   feasible to build such computers; however, RSA, DSA, ECDSA, and EdDSA
   are all vulnerable if large-scale quantum computers come to pass.

   Since the HSS/LMS signature algorithm does not depend on the
   difficulty of discrete logarithm or factoring, the HSS/LMS signature
   algorithm is considered to be post-quantum secure.  The use of HSS/
   LMS hash-based signatures to protect software update distribution,
   perhaps using the format that is being specified by the IETF SUIT
   Working Group, will allow the deployment of software that implements
   new cryptosystems.

1.2.  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.

2.  LMS Digital Signature Algorithm Overview

   This specification makes use of the hash-based signature algorithm
   specified in [HASHSIG], which is the Leighton and Micali adaptation
   [LM] of the original Lamport-Diffie-Winternitz-Merkle one-time
   signature system [M1979][M1987][M1989a][M1989b].

   The hash-based signature algorithm has three major components:

      o  Hierarchical Signature System (HSS) -- see Section 2.1;

      o  Leighton-Micali Signature (LMS) -- see Section 2.2; and

      o  Leighton-Micali One-time Signature Algorithm (LM-OTS) -- see
            Section 2.3.




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   As implied by the name, the hash-based signature algorithm depends on
   a collision-resistant hash function.  The the hash-based signature
   algorithm specified in [HASHSIG] currently makes use of the SHA-256
   one-way hash function [SHS], but it also establishes an IANA registry
   to permit the registration of additional one-way hash functions in
   the future.

2.1.  Hierarchical Signature System (HSS)

   The hash-based signature algorithm specified in [HASHSIG] uses a
   hierarchy of trees.  The Hierarchical N-time Signature System (HSS)
   allows subordinate trees to be generated when needed by the signer.
   Otherwise, generation of the entire tree might take weeks or longer.

   An HSS signature as specified in [HASHSIG] carries the number of
   signed public keys (Nspk), followed by that number of signed public
   keys, followed by the LMS signature as described in Section 2.2.  The
   public key for the top-most LMS tree is the public key of the HSS
   system.  The LMS private key in the parent tree signs the LMS public
   key in the child tree, and the LMS private key in the bottom-most
   tree signs the actual message.  The signature over the public key and
   the signature over the actual message are LMS signatures as described
   in Section 2.2.

   The elements of the HSS signature value for a stand-alone tree (a top
   tree with no children) can be summarized as:

      u32str(0) ||
      lms_signature  /* signature of message */

   The elements of the HSS signature value for a tree with Nspk signed
   public keys can be summarized as:

      u32str(Nspk) ||
      signed_public_key[0] ||
      signed_public_key[1] ||
         ...
      signed_public_key[Nspk-2] ||
      signed_public_key[Nspk-1] ||
      lms_signature  /* signature of message */

   where, as defined in Section 3.3 of [HASHSIG], a signed_public_key is
   the lms_signature over the public key followed by the public key
   itself.  Note that Nspk is the number of levels in the hierarchy of
   trees minus 1.






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2.2.  Leighton-Micali Signature (LMS)

   Each tree in the hash-based signature algorithm specified in
   [HASHSIG] uses the Leighton-Micali Signature (LMS) system.  LMS
   systems have two parameters.  The first parameter is the height of
   the tree, h, which is the number of levels in the tree minus one.
   The [HASHSIG] includes support for five values of this parameter:
   h=5; h=10; h=15; h=20; and h=25.  Note that there are 2^h leaves in
   the tree.  The second parameter is the number of bytes output by the
   hash function, m, which is the amount of data associated with each
   node in the tree.  This specification supports only SHA-256, with
   m=32.  An IANA registry is defined so that other hash functions could
   be used in the future.

   The [HASHSIG] specification supports five tree sizes:

      LMS_SHA256_M32_H5;
      LMS_SHA256_M32_H10;
      LMS_SHA256_M32_H15;
      LMS_SHA256_M32_H20; and
      LMS_SHA256_M32_H25.

   The [HASHSIG] specification establishes an IANA registry to permit
   the registration of additional hash functions and additional tree
   sizes in the future.

   The [HASHSIG] specification defines the value I as the private key
   identifier, and the same I value is used for all computations with
   the same LMS tree.  In addition, the [HASHSIG] specification defines
   the value T[i] as the m-byte string associated with the ith node in
   the LMS tree, where and the nodes are indexed from 1 to 2^(h+1)-1.
   Thus, T[1] is the m-byte string associated with the root of the LMS
   tree.

   The LMS public key can be summarized as:

      u32str(lms_algorithm_type) || u32str(otstype) || I || T[1]

   As specified in [HASHSIG], the LMS signature consists of four
   elements: the number of the leaf associated with the LM-OTS
   signature, an LM-OTS signature as described in Section 2.3, a
   typecode indicating the particular LMS algorithm, and an array of
   values that is associated with the path through the tree from the
   leaf associated with the LM-OTS signature to the root.  The array of
   values contains the siblings of the nodes on the path from the leaf
   to the root but does not contain the nodes on the path itself.  The
   array for a tree with height h will have h values.  The first value




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   is the sibling of the leaf, the next value is the sibling of the
   parent of the leaf, and so on up the path to the root.

   The four elements of the LMS signature value can be summarized as:

      u32str(q) ||
      ots_signature ||
      u32str(type) ||
      path[0] || path[1] || ... || path[h-1]

2.3.  Leighton-Micali One-time Signature Algorithm (LM-OTS)

   The hash-based signature algorithm depends on a one-time signature
   method.  This specification makes use of the Leighton-Micali One-time
   Signature Algorithm (LM-OTS) [HASHSIG].  An LM-OTS has five
   parameters:

      n -  The number of bytes output by the hash function.  This
           specification supports only SHA-256 [SHS], with n=32.

      H -  A preimage-resistant hash function that accepts byte strings
           of any length, and returns an n-byte string.  This
           specification supports only SHA-256 [SHS].

      w -  The width in bits of the Winternitz coefficients.  [HASHSIG]
           supports four values for this parameter: w=1; w=2; w=4; and
           w=8.

      p -  The number of n-byte string elements that make up the LM-OTS
           signature.

      ls - The number of left-shift bits used in the checksum function,
           which is defined in Section 4.5 of [HASHSIG].

   The values of p and ls are dependent on the choices of the parameters
   n and w, as described in Appendix B of [HASHSIG].

   The [HASHSIG] specification supports four LM-OTS variants:

      LMOTS_SHA256_N32_W1;
      LMOTS_SHA256_N32_W2;
      LMOTS_SHA256_N32_W4; and
      LMOTS_SHA256_N32_W8.

   The [HASHSIG] specification establishes an IANA registry to permit
   the registration of additional hash functions and additional
   parameter sets in the future.




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   Signing involves the generation of C, which is an n-byte random
   value.

   The LM-OTS signature value can be summarized as the identifier of the
   LM-OTS variant, the random value, and a sequence of hash values (y[0]
   through y[p-1]) that correspond to the elements of the public key as
   described in Section 4.5 of [HASHSIG]:

      u32str(otstype) || C || y[0] || ... || y[p-1]

3.  Hash-based Signature Algorithm Identifiers

   The CBOR Object Signing and Encryption (COSE) [RFC8152] supports two
   signature algorithm schemes.  This specification makes use of the
   signature with appendix scheme for hash-based signatures.

   The signature value is a large byte string as described in Section 2.
   The byte string is designed for easy parsing.  The HSS, LMS, and
   LMOTS components of the signature value format include counters and
   type codes that indirectly provide all of the information that is
   needed to parse the byte string during signature validation.

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

      o  The 'kty' field MUST be present, and it MUST be 'HSS-LMS'.

      o  If the 'alg' field is present, and it MUST be 'HSS-LMS'.

      o  If the 'key_ops' field is present, it MUST include 'sign' when
           creating a hash-based signature.

      o  If the 'key_ops' field is present, it MUST include 'verify'
           when verifying a hash-based signature.

      o  If the 'kid' field is present, it MAY be used to identify the
           top of the HSS tree.  In [HASHSIG], this identifier is called
           'I', and it is the 16-byte identifier of the LMS public key
           for the tree.

4.  Security Considerations

4.1.  Implementation Security Considerations

   Implementations MUST protect the private keys.  Compromise of the
   private keys may result in the ability to forge signatures.  Along
   with the private key, the implementation MUST keep track of which
   leaf nodes in the tree have been used.  Loss of integrity of this



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   tracking data can cause a one-time key to be used more than once.  As
   a result, when a private key and the tracking data are stored on non-
   volatile media or stored in a virtual machine environment, failed
   writes, virtual machine snapshotting or cloning, and other
   operational concerns must be considered to ensure confidentiality and
   integrity.

   When generating an LMS key pair, an implementation MUST generate each
   key pair independently of all other key pairs in the HSS tree.

   An implementation MUST ensure that a LM-OTS private key is used to
   generate a signature only one time, and ensure that it cannot be used
   for any other purpose.

   The generation of private keys relies on random numbers.  The use of
   inadequate pseudo-random number generators (PRNGs) to generate these
   values can result in little or no security.  An attacker may find it
   much easier to reproduce the PRNG environment that produced the keys,
   searching the resulting small set of possibilities, rather than brute
   force searching the whole key space.  The generation of quality
   random numbers is difficult, and [RFC4086] offers important guidance
   in this area.

   The generation of hash-based signatures also depends on random
   numbers.  While the consequences of an inadequate pseudo-random
   number generator (PRNG) to generate these values is much less severe
   than in the generation of private keys, the guidance in [RFC4086]
   remains important.

5.  Operational Considerations

   The public key for the hash-based signature is the key at the root of
   Hierarchical Signature System (HSS).  In the absence of a public key
   infrastructure [RFC5280], this public key is a trust anchor, and the
   number of signatures that can be generated is bounded by the size of
   the overall HSS set of trees.  When all of the LM-OTS signatures have
   been used to produce a signature, then the establishment of a new
   trust anchor is required.

   To ensure that none of tree nodes are used to generate more than one
   signature, the signer maintains state across different invocations of
   the signing algorithm.  Section 12.2 of [HASHSIG] offers some
   practical implementation approaches around this statefulness.  In
   some of these approaches, nodes are sacrificed to ensure that none
   are used more than once.  As a result, the total number of signatures
   that can be generated might be less than the overall HSS set of
   trees.




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6.  IANA Considerations

   IANA is requested to add entries for hash-based signatures in the
   "COSE Algorithms" registry and hash-based public keys in the "COSE
   Key Types" registry.

6.1.  COSE Algorithms Registry Entry

   The new entry in the "COSE Algorithms" registry has the following
   columns:

      Name:  HSS-LMS

      Value:  TBD (Value between -256 and 255 to be assigned by IANA)

      Description:  HSS/LMS hash-based digital signature

      Reference:  This document (Number to be assigned by RFC Editor)

      Recommended:  Yes

6.2.  COSE Key Types Registry Entry

   The new entry in the "COSE Key Types" registry has the following
   columns:

      Name:  HSS-LMS

      Value:  TBD (Value to be assigned by IANA)

      Description:  Public key for HSS/LMS hash-based digital signature

      Reference:  This document (Number to be assigned by RFC Editor)

7.  References

7.1.  Normative References

   [HASHSIG]  McGrew, D., Curcio, M., and S. Fluhrer, "Leighton-Micali
              Hash-Based Signatures", RFC 8554, April 2019,
              <https://rfc-editor.org/rfc/rfc8554.txt>.

   [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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   [RFC8152]  Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              RFC 8152, DOI 10.17487/RFC8152, July 2017,
              <https://www.rfc-editor.org/info/rfc8152>.

   [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>.

   [SHS]      National Institute of Standards and Technology (NIST),
              "Secure Hash Standard", FIPS Publication 180-3, 2008.

7.2.  Informative References

   [BH2013]   Ptacek, T., Ritter, T., Samuel, J., and A. Stamos, "The
              Factoring Dead: Preparing for the Cryptopocalypse", August
              2013, <https://media.blackhat.com/us-13/us-13-Stamos-The-
              Factoring-Dead.pdf>.

   [LM]       Leighton, F. and S. Micali, "Large provably fast and
              secure digital signature schemes from secure hash
              functions", U.S. Patent 5,432,852, July 1995.

   [M1979]    Merkle, R., "Secrecy, Authentication, and Public Key
              Systems", Stanford University Information Systems
              Laboratory Technical Report 1979-1, 1979.

   [M1987]    Merkle, R., "A Digital Signature Based on a Conventional
              Encryption Function", Lecture Notes in Computer
              Science crypto87, 1988.

   [M1989a]   Merkle, R., "A Certified Digital Signature", Lecture Notes
              in Computer Science crypto89, 1990.

   [M1989b]   Merkle, R., "One Way Hash Functions and DES", Lecture
              Notes in Computer Science crypto89, 1990.

   [NAS2019]  National Academies of Sciences, Engineering, and Medicine,
              "Quantum Computing: Progress and Prospects", 2019,
              <http://dx.doi.org/10.17226/25196>.

   [PQC]      Bernstein, D., "Introduction to post-quantum
              cryptography", 2009,
              <http://www.pqcrypto.org/www.springer.com/cda/content/
              document/cda_downloaddocument/9783540887010-c1.pdf>.







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   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,
              <https://www.rfc-editor.org/info/rfc4086>.

   [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>.

Appendix A.  Examples

   This appendix provides a non-normative example of a COSE full message
   signature and an example of a COSE_Sign0 message.  The display format
   includes "\" to indicate that the same field continues on the next
   line, and it includes "|" to separate items within a field.

   The programs that were used to generate the examples can be found at
   https://github.com/cose-wg/Examples.

A.1.  Example COSE Full Message Signature

   This section provides an example of a COSE full message signature.

   {
      "title":"HSS LMS Hash based signature - hsssig-01",
      "input":{
         "plaintext":"This is the content.",
         "sign":{
            "protected":{
               "ctyp":0
            },
            "signers":[
               {
                  "key":{
                     "kty":"HSS-LMS",
                     "kid":"ItsBig",
                     "comment":"1 level key - LM_SHA256_MD32_H10 + \
                         LMOTS_SHA256_N32_W4 ",
                     "public":"000000010000000600000003d08fabd4a20 \
                         91ff0a8cb4ed834e7453432a58885cd9ba0431235 \
                         466bff9651c6c92124404d45fa53cf161c28f1ad5a8e",
                     "private":"1|6|3|558B8966C48AE9CB898B423C8344 \
                         3AAE014A72F1B1AB5CC85CF1D892903B5439|1|d0 \
                         8fabd4a2091ff0a8cb4ed834e74534"
                  },
                  "unprotected":{



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                     "kid":"ItsBig"
                  },
                  "protected":{
                     "alg":"HSS-LMS"
                  }
               }
            ]
         },
         "rng_description":"Random value for signature",
         "rng_stream":[
            "ACFC5C7377D45C969DF7D7289882A48C1A10E5C48B6E29DF5018D \
                3E683E36BC5"
         ]
      },
      "intermediates":{
         "signers":[
            {
               "ToBeSign_hex":"85695369676E617475726543A103004AA10 \
                   1674853532D4C4D53405454686973206973207468652063 \
                   6F6E74656E742E"
            }
         ]
      },
      "output":{
         "cbor_diag":"98([h'A10300', {}, h'54686973206973207468652 \
             0636F6E74656E742E', [[h'A101674853532D4C4D53', \
             {4: h'497473426967'}, h'00000000000000010000000391291 \
             DE76CE6E24D1E2A9B60266519BC8CE889F814DEB0FC00EDD3129D \
             E3AB9BFC0F5DA46923923AA3209BF9E1480AB78906D79D4C9280A \
             DC6300C182CB33429CE0035FE3E2E4428770D22F85687A18AEE76 \
             CDC2F8E8F40043B314A68E72F9F679F7E3A5A34594E7673EEB70E \
             840FBFFDA398EC59BF0236FDD34ACE319DC1EAD1BD22B0213A094 \
             6160F30168A6E193C57C32BB017C22529EC3760FF93358633D5A6 \
             9F7F0850BD720E72FF758B19D4E27D114B1E6321BFDF1859102E7 \
             23A3B1F1AE5BC53EC8732FF1B2C4D384137E8EEEC94804CB47C82 \
             3C0B01441E28B178E1F5A904CF7592AAACF820C97E7714B69FCA4 \
             BABE97854B0C00A705CAE7BA9112D182C21BCE3F10EA70C324F46 \
             6749279610A3477B03E3622169438C27CD46FCAD769D010D0B13A \
             06F5CD00D93A2EEB2BB0E25BFFD2A08C8DDF0653518B7BFEDB3B4 \
             6EB56BDA75B0421DF87F7FD1F08808B58DD3647472D90F8F9459C \
             775BFF5930956EBD7BF4D5F6B26BC53196FF9B660949B23154B9C \
             E7A0DF55E9083B42A90D82F8D1DE2F62770EBDCE42A4A50448854 \
             15C7BA81EFED2BCF8C1B6932215646E9EF160DDD79CA4DD6F4774 \
             85BB5B01AAD4DF4D6D45942B935C74D35BD340D9D83CBC8F8A719 \
             D6BB5CE098091C8787E193C84CE386355C55807A17CE1BFF830D4 \
             B87D63646EF8FC1E9E9071BB67A123FDEC3F37638CDAF0F4BF308 \
             4074069171C10C4670163B9626635ADE3BD6D7917D0B029C7D4B8 \
             8B005473B6FF3862FB491CD1E1F6069B306C4EF8AE4C7F83EB320 \



Housley                  Expires April 30, 2020                [Page 12]


Internet-Draft              HashSig with COSE               October 2019


             A20406AA7FFF84BFDD22AD876B4661ED5D38F35591625F1D53DC1 \
             BD472D1B4D93E93DA31A8CD5CEA70B6DD7BCFA510E5BD31C1AA60 \
             BD252071D689C9D9CC1EDFE8AA0235C654F758FC8936515AE3441 \
             C3B9F2AFFA164AF2999C6994C54F0AC923F0E6ED8C48C6148234E \
             ADB87ABEA3C935B3D9682E6D121506131E6928474327E1E47CE7C \
             9D9BD4C36E7A274664B21B1E6304CCD6111E53159775196AAC4D5 \
             9ED5FF553F4EC9597DF17873BB5E47827D83AA48BD22849D5A97C \
             93A106672BDEB52ED7B6D2C56CE32700513C0FC04F26549A6FC5C \
             DBB5634C0BFBB6EF1FAADA66923D21BAB3BF62C6DD6D7DAAB67AB \
             A8923C4CF1CC8ABB47F33DF12617C38A7B1DB13E6B2D6E23DFA59 \
             F8E760966B7B17A5B492C6AE25920E8F697F7666D02222CD48852 \
             7DB55DAABD2F82D927BBB7EC06B833D4BBE08680A54B1E062D938 \
             8530B1F96696F712457AF44705400D8F443FAFB01D76FD6075D20 \
             845044ACCEA54DC4872A97C2DBCF0A9968001CB7C22F9D9387A76 \
             630FE4A825AA4054A3E5BA1486F5AD7B2A87FD4B248DCEE4E6EC1 \
             A2B8A2D2BFB19A74CA3027338633B18865EB5A16997D2DD3BC441 \
             35E47220182BC1FB7445037C3524641CF69370D0627C04C43A14E \
             778BADCFD7961551A9FCB95A8D4162A94110BC703F5F49CB85322 \
             CA9007322F2DBE55DC237FAED2FBF9C953EF9F5EBBDC0058BFD69 \
             475A87D32E4A9E5C266012B0CCE1E507AD10FC01D7E00FBF5556E \
             A9DC716B812357F0BE844FD14C33C582E80EB1603D78C00A6E9F6 \
             7EB8981A04581122F3F0DDCF997F6F7CB637857C07DEC7353DA14 \
             03BAAFAC8DB374922198081D77F52DB3F8B6281471D53BB11C6DA \
             56DD733632021F584E207FD61222C4FFEFAA74214C7634B6171C9 \
             5905CA05D9A3A686A7BA541BFA59A76F9CB85F4A5272BC6209A41 \
             CF83A22EF22074B2760118952B8282ACEF179B26C879D2C8B4238 \
             979E4BD512D8A5D20578810E134F254B4C1D22685B58537632259 \
             BB6B4CC14FB6E6C94C1087441A81F11B9A83535B24DDC725A81A9 \
             D1FF62DA2804C8D84C6E3837D97DEF03AA275D348E7C0AA4A46A3 \
             9EDDDD55C45513AB692BD7DEC0F0B142F3E7075CBEA436F3791AF \
             2C6E014F73C8A29464393BBB56ACE6A7048F1E444934125C9B5F7 \
             8A5AA130F238A441DBEC5EA73F61D00D059CB2A137D6F9EC27306 \
             8B2545549E525055CDE70F7C7C28FB4CADC251AE6FE3186DF1987 \
             0661831E95C76450146654A3D36184CFFAA1EFC684ACD21D2498E \
             298FD18E99D5C6AFAF5588CCDDC2475B9E8294677924FA8283094 \
             810F7DD9FEF57DFF359805725ED044AC13D1794D7949FE0EAFC42 \
             5933A7D788035C6C825A580EC3E26F7B3BE31FB98A7F67BCC6FF5 \
             1ABEA2A7D9FF6D898018B5FBEE74D892C8694101236E20991499D \
             0385A18B290BCF2938806D602E27800C21B2E38C65B987B10D360 \
             B2C674EED6A6205F251A0E68B7D57060DE5E3F599BA197997EE49 \
             DA7D6AB97119F03AF737CE914B004462AA07C61B15311BBA10FC5 \
             BB68A2621E47BE3374222DFFDE29C7910418F6D9E4DD1B7B7A9B3 \
             600689019F188EA696B7951A10C15E9BD01A5160E1A571942E223 \
             C6F29A70528E5CF7A52F1F60806A9FF729E76D69BFD315383F031 \
             C3863650757F1EF75D474935147FBAA9A6DA0ABF7C5BCF4E05026 \
             FD134AC20815A3A81A026213EA50FF1454F2399518DD359D49D9E \
             475DA432FFD4B953875FDB7A7EA7D04AC13D4102851D90BAB6527 \
             72527E85C485E863D9A1AC76BC0474D53FA5E6A77E64210788FBD \



Housley                  Expires April 30, 2020                [Page 13]


Internet-Draft              HashSig with COSE               October 2019


             EB5696C6DEEEDF18AAC2BC74FC861AB770175A032273E4D5D7366 \
             C8FFE6F446995B564FC3D59C70FECDB60A25E28650417157F43F3 \
             E72C3AFC2372EC9D0787CB37BFAC383648E7A168EAACCA7C55505 \
             F93E9A09310320CB5184512F583F2FEA5853C36E6E43A6E6BE182 \
             185F04FE4B05170865618A51CF25542EADF473D5794295BDC86FC \
             6909D301E952346E32D69320D333BCA39B4FF8AF7E199BD55D919 \
             0F1FED4D3225274F03A1806E201ED2D040509FD7FA67C9CE6068E \
             C54B56D53BF47E67B5B8B6382A0CB69A61D7FBC2DDEDA171D4F70 \
             14262FC77F454A3E68E6EFB7C31C4080024C8027FD8D6CE648B78 \
             2B56B762BEE5ADA237D018689B58902CBAC4E44C931416B47CD5E \
             20026D5B81B407A0E29CAAEC81F1C3528463132F00589A9F8021A \
             74109F8DBF81FE282C1F58BF3F2A52C560E38BFD68B2D28679CBC \
             089F2C9C3FC245FF5FA3ADA7F7973D9BD4BEC69B1F0C71416A6C4 \
             F00000006ED1CE8C6E437918D43FBA7BD9385694C41182703F6B7 \
             F704DEEDD9384BA6F8BC362C948646B3C9848803E6D9BA1F7D396 \
             7F709CDDD35DC77D60356F0C36808900B491CB4ECBBABEC128E7C \
             81A46E62A67B57640A0A78BE1CBF7DD9D419A10CD8686D16621A8 \
             0816BFDB5BDC56211D72CA70B81F1117D129529A7570CF79CF52A \
             7028A48538ECDD3B38D3D5D62D26246595C4FB73A525A5ED2C305 \
             24EBB1D8CC82E0C19BC4977C6898FF95FD3D310B0BAE71696CEF9 \
             3C6A552456BF96E9D075E383BB7543C675842BAFBFC7CDB88483B \
             3276C29D4F0A341C2D406E40D4653B7E4D045851ACF6A0A0EA9C7 \
             10B805CCED4635EE8C107362F0FC8D80C14D0AC49C516703D26D1 \
             4752F34C1C0D2C4247581C18C2CF4DE48E9CE949BE7C888E9CAEB \
             E4A415E291FD107D21DC1F084B1158208249F28F4F7C7E931BA7B \
             3BD0D824A4570']]])",
         "cbor":"D8628443A10300A054546869732069732074686520636F6E7 \
             4656E742E81834AA101674853532D4C4D53A10446497473426967 \
             5909D000000000000000010000000391291DE76CE6E24D1E2A9B6 \
             0266519BC8CE889F814DEB0FC00EDD3129DE3AB9BFC0F5DA46923 \
             923AA3209BF9E1480AB78906D79D4C9280ADC6300C182CB33429C \
             E0035FE3E2E4428770D22F85687A18AEE76CDC2F8E8F40043B314 \
             A68E72F9F679F7E3A5A34594E7673EEB70E840FBFFDA398EC59BF \
             0236FDD34ACE319DC1EAD1BD22B0213A0946160F30168A6E193C5 \
             7C32BB017C22529EC3760FF93358633D5A69F7F0850BD720E72FF \
             758B19D4E27D114B1E6321BFDF1859102E723A3B1F1AE5BC53EC8 \
             732FF1B2C4D384137E8EEEC94804CB47C823C0B01441E28B178E1 \
             F5A904CF7592AAACF820C97E7714B69FCA4BABE97854B0C00A705 \
             CAE7BA9112D182C21BCE3F10EA70C324F466749279610A3477B03 \
             E3622169438C27CD46FCAD769D010D0B13A06F5CD00D93A2EEB2B \
             B0E25BFFD2A08C8DDF0653518B7BFEDB3B46EB56BDA75B0421DF8 \
             7F7FD1F08808B58DD3647472D90F8F9459C775BFF5930956EBD7B \
             F4D5F6B26BC53196FF9B660949B23154B9CE7A0DF55E9083B42A9 \
             0D82F8D1DE2F62770EBDCE42A4A5044885415C7BA81EFED2BCF8C \
             1B6932215646E9EF160DDD79CA4DD6F477485BB5B01AAD4DF4D6D \
             45942B935C74D35BD340D9D83CBC8F8A719D6BB5CE098091C8787 \
             E193C84CE386355C55807A17CE1BFF830D4B87D63646EF8FC1E9E \
             9071BB67A123FDEC3F37638CDAF0F4BF3084074069171C10C4670 \



Housley                  Expires April 30, 2020                [Page 14]


Internet-Draft              HashSig with COSE               October 2019


             163B9626635ADE3BD6D7917D0B029C7D4B88B005473B6FF3862FB \
             491CD1E1F6069B306C4EF8AE4C7F83EB320A20406AA7FFF84BFDD \
             22AD876B4661ED5D38F35591625F1D53DC1BD472D1B4D93E93DA3 \
             1A8CD5CEA70B6DD7BCFA510E5BD31C1AA60BD252071D689C9D9CC \
             1EDFE8AA0235C654F758FC8936515AE3441C3B9F2AFFA164AF299 \
             9C6994C54F0AC923F0E6ED8C48C6148234EADB87ABEA3C935B3D9 \
             682E6D121506131E6928474327E1E47CE7C9D9BD4C36E7A274664 \
             B21B1E6304CCD6111E53159775196AAC4D59ED5FF553F4EC9597D \
             F17873BB5E47827D83AA48BD22849D5A97C93A106672BDEB52ED7 \
             B6D2C56CE32700513C0FC04F26549A6FC5CDBB5634C0BFBB6EF1F \
             AADA66923D21BAB3BF62C6DD6D7DAAB67ABA8923C4CF1CC8ABB47 \
             F33DF12617C38A7B1DB13E6B2D6E23DFA59F8E760966B7B17A5B4 \
             92C6AE25920E8F697F7666D02222CD488527DB55DAABD2F82D927 \
             BBB7EC06B833D4BBE08680A54B1E062D9388530B1F96696F71245 \
             7AF44705400D8F443FAFB01D76FD6075D20845044ACCEA54DC487 \
             2A97C2DBCF0A9968001CB7C22F9D9387A76630FE4A825AA4054A3 \
             E5BA1486F5AD7B2A87FD4B248DCEE4E6EC1A2B8A2D2BFB19A74CA \
             3027338633B18865EB5A16997D2DD3BC44135E47220182BC1FB74 \
             45037C3524641CF69370D0627C04C43A14E778BADCFD7961551A9 \
             FCB95A8D4162A94110BC703F5F49CB85322CA9007322F2DBE55DC \
             237FAED2FBF9C953EF9F5EBBDC0058BFD69475A87D32E4A9E5C26 \
             6012B0CCE1E507AD10FC01D7E00FBF5556EA9DC716B812357F0BE \
             844FD14C33C582E80EB1603D78C00A6E9F67EB8981A04581122F3 \
             F0DDCF997F6F7CB637857C07DEC7353DA1403BAAFAC8DB3749221 \
             98081D77F52DB3F8B6281471D53BB11C6DA56DD733632021F584E \
             207FD61222C4FFEFAA74214C7634B6171C95905CA05D9A3A686A7 \
             BA541BFA59A76F9CB85F4A5272BC6209A41CF83A22EF22074B276 \
             0118952B8282ACEF179B26C879D2C8B4238979E4BD512D8A5D205 \
             78810E134F254B4C1D22685B58537632259BB6B4CC14FB6E6C94C \
             1087441A81F11B9A83535B24DDC725A81A9D1FF62DA2804C8D84C \
             6E3837D97DEF03AA275D348E7C0AA4A46A39EDDDD55C45513AB69 \
             2BD7DEC0F0B142F3E7075CBEA436F3791AF2C6E014F73C8A29464 \
             393BBB56ACE6A7048F1E444934125C9B5F78A5AA130F238A441DB \
             EC5EA73F61D00D059CB2A137D6F9EC273068B2545549E525055CD \
             E70F7C7C28FB4CADC251AE6FE3186DF19870661831E95C7645014 \
             6654A3D36184CFFAA1EFC684ACD21D2498E298FD18E99D5C6AFAF \
             5588CCDDC2475B9E8294677924FA8283094810F7DD9FEF57DFF35 \
             9805725ED044AC13D1794D7949FE0EAFC425933A7D788035C6C82 \
             5A580EC3E26F7B3BE31FB98A7F67BCC6FF51ABEA2A7D9FF6D8980 \
             18B5FBEE74D892C8694101236E20991499D0385A18B290BCF2938 \
             806D602E27800C21B2E38C65B987B10D360B2C674EED6A6205F25 \
             1A0E68B7D57060DE5E3F599BA197997EE49DA7D6AB97119F03AF7 \
             37CE914B004462AA07C61B15311BBA10FC5BB68A2621E47BE3374 \
             222DFFDE29C7910418F6D9E4DD1B7B7A9B3600689019F188EA696 \
             B7951A10C15E9BD01A5160E1A571942E223C6F29A70528E5CF7A5 \
             2F1F60806A9FF729E76D69BFD315383F031C3863650757F1EF75D \
             474935147FBAA9A6DA0ABF7C5BCF4E05026FD134AC20815A3A81A \
             026213EA50FF1454F2399518DD359D49D9E475DA432FFD4B95387 \



Housley                  Expires April 30, 2020                [Page 15]


Internet-Draft              HashSig with COSE               October 2019


             5FDB7A7EA7D04AC13D4102851D90BAB652772527E85C485E863D9 \
             A1AC76BC0474D53FA5E6A77E64210788FBDEB5696C6DEEEDF18AA \
             C2BC74FC861AB770175A032273E4D5D7366C8FFE6F446995B564F \
             C3D59C70FECDB60A25E28650417157F43F3E72C3AFC2372EC9D07 \
             87CB37BFAC383648E7A168EAACCA7C55505F93E9A09310320CB51 \
             84512F583F2FEA5853C36E6E43A6E6BE182185F04FE4B05170865 \
             618A51CF25542EADF473D5794295BDC86FC6909D301E952346E32 \
             D69320D333BCA39B4FF8AF7E199BD55D9190F1FED4D3225274F03 \
             A1806E201ED2D040509FD7FA67C9CE6068EC54B56D53BF47E67B5 \
             B8B6382A0CB69A61D7FBC2DDEDA171D4F7014262FC77F454A3E68 \
             E6EFB7C31C4080024C8027FD8D6CE648B782B56B762BEE5ADA237 \
             D018689B58902CBAC4E44C931416B47CD5E20026D5B81B407A0E2 \
             9CAAEC81F1C3528463132F00589A9F8021A74109F8DBF81FE282C \
             1F58BF3F2A52C560E38BFD68B2D28679CBC089F2C9C3FC245FF5F \
             A3ADA7F7973D9BD4BEC69B1F0C71416A6C4F00000006ED1CE8C6E \
             437918D43FBA7BD9385694C41182703F6B7F704DEEDD9384BA6F8 \
             BC362C948646B3C9848803E6D9BA1F7D3967F709CDDD35DC77D60 \
             356F0C36808900B491CB4ECBBABEC128E7C81A46E62A67B57640A \
             0A78BE1CBF7DD9D419A10CD8686D16621A80816BFDB5BDC56211D \
             72CA70B81F1117D129529A7570CF79CF52A7028A48538ECDD3B38 \
             D3D5D62D26246595C4FB73A525A5ED2C30524EBB1D8CC82E0C19B \
             C4977C6898FF95FD3D310B0BAE71696CEF93C6A552456BF96E9D0 \
             75E383BB7543C675842BAFBFC7CDB88483B3276C29D4F0A341C2D \
             406E40D4653B7E4D045851ACF6A0A0EA9C710B805CCED4635EE8C \
             107362F0FC8D80C14D0AC49C516703D26D14752F34C1C0D2C4247 \
             581C18C2CF4DE48E9CE949BE7C888E9CAEBE4A415E291FD107D21 \
             DC1F084B1158208249F28F4F7C7E931BA7B3BD0D824A4570"
      }
   }

A.2.  Example COSE_Sign0 Message

   This section provides an example of a COSE_Sign0 message.

   {
      "title":"HSS LMS Hash based signature - hsssig-sig-01",
      "input":{
         "plaintext":"This is the content.",
         "sign0":{
            "key":{
               "kty":"HSS-LMS",
               "kid":"ItsBig",
               "comment":"1 level key - LM_SHA256_MD32_H10 + \
                   LMOTS_SHA256_N32_W4 ",
               "public":"000000010000000600000003d08fabd4a2091ff0a \
                   8cb4ed834e7453432a58885cd9ba0431235466bff9651c6 \
                   c92124404d45fa53cf161c28f1ad5a8e",
               "private":"1|6|3|558B8966C48AE9CB898B423C83443AAE01 \



Housley                  Expires April 30, 2020                [Page 16]


Internet-Draft              HashSig with COSE               October 2019


                   4A72F1B1AB5CC85CF1D892903B5439|0|d08fabd4a2091f \
                   f0a8cb4ed834e74534"
            },
            "unprotected":{
               "kid":"ItsBig"
            },
            "protected":{
               "alg":"HSS-LMS"
            },
            "alg":"HSS-LMS"
         },
         "rng_description":"Random value for signature",
         "rng_stream":[
            "1D5112D38A1146402875B73BC8D4B59C845C6AE61D03A70ABAD09 \
            8AC05AD8297"
         ]
      },
      "intermediates":{
         "ToBeSign_hex":"846A5369676E6174757265314AA101674853532D4 \
         C4D534054546869732069732074686520636F6E74656E742E"
      },
      "output":{
         "cbor_diag":"18([h'A101674853532D4C4D53', \
             {4: h'497473426967'}, \
             h'546869732069732074686520636F6E74656E742E', \
             h'00000000000000000000000391291DE76CE6E24D1E2A9B60266 \
             519BC8CE889F814DEB0FC00EDD3129DE3AB9BA6814A4BEE84E5E8 \
             38C7725F78FE0610837A548F92802DA610AFB0ADFB133123061C0 \
             23E87A7802C17B00740F25737A775B95E923905B6F0CA02A87095 \
             5420A68003133A1EA12083E134238DFE5F1633E159CFD207BC79B \
             50DD39BA39FCAAA75C12F7F1B493AB8736162E42C2C2F9159DF33 \
             32C399A50BB8404F2CB6D98DAA4C3DF82A197CFE014BEC27CC820 \
             A5B26BAC5DFE05947E3A7D92070A4653C67BA095AB0499AF655B8 \
             1B719912E296765FA46CB0AD2ED56BBCF00CA6FB9C16D8C05C1C1 \
             65FED054A099A3DA89F9CB951C6ED366DF38E299C7E7DC9AC9C43 \
             66F328407E7C4A6CD8A5314D6B02B377406D5A5E589E91FEAA9F2 \
             E4EC1682BA1F633C7784B3038FAC2E77947916C8F4160CF6D9D0B \
             0BC6600CDBC4AE947DD5D317DCBA3D200A739F96CDDBA94DAF86C \
             E80C76158D4F5CF3CD2BA9F1393DF47E556887F919E0718625D31 \
             240E7FE9599012F757314C20893827194AD6555F1452E3A749CE2 \
             13DFBA283013DCFF196F9BD18D715B6E7451DE35B18181DF8A626 \
             DE1480F2DDECB126B477E019FFE75E4472EF4FA1B913C80821155 \
             AAE0D7F3B1175B64CA076926166C80E8219D241791C1DE3C8F936 \
             55085C0B00F840970367DAF2A41D462C696C74AF0C3591A6C6B4D \
             701963819FFBDC945785D64CE687BA4D086A31FE6A5E1C74A6C0E \
             25CF67CEA24DCDE0E47B5210670CC2D66003DF2232F4BA337D325 \
             166381681FD4738997BB3EC1499E594B5CCE9FBC11C3136C20F15 \
             6012A4DA062675627758DBF1BE635C876F81713D322EA127F6FFC \



Housley                  Expires April 30, 2020                [Page 17]


Internet-Draft              HashSig with COSE               October 2019


             8880F42BA51879CC0EB27B8A0C21E434DA7C490BFE30BE1FAC3CA \
             A5CF97451FADF412ECA7BAD72E2553541224EB934A9C8A0034E1C \
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             44F95AEF50A1E44761E5E25670DA2C7291254C17C298F685B1FB0 \



Housley                  Expires April 30, 2020                [Page 18]


Internet-Draft              HashSig with COSE               October 2019


             22932B07DE031B1E9988131C73BD0B4E748FF2C2FFD45B7DF99EF \
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             738997BB3EC1499E594B5CCE9FBC11C3136C20F156012A4DA0626 \



Housley                  Expires April 30, 2020                [Page 19]


Internet-Draft              HashSig with COSE               October 2019


             75627758DBF1BE635C876F81713D322EA127F6FFC8880F42BA518 \
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             44FD07847B86A544AAB532DD2E49C2ACB9C42330B44F95AEF50A1 \



Housley                  Expires April 30, 2020                [Page 20]


Internet-Draft              HashSig with COSE               October 2019


             E44761E5E25670DA2C7291254C17C298F685B1FB022932B07DE03 \
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             4D0AC49C516703D26D14752F34C1C0D2C4247581C18C2CF4DE48E \
             9CE949BE7C888E9CAEBE4A415E291FD107D21DC1F084B11582082 \
             49F28F4F7C7E931BA7B3BD0D824A4570"
      }
   }

Appendix B.  Acknowledgements

   Many thanks to Roman Danyliw, Scott Fluhrer, John Mattsson, Jim
   Schaad, and Tony Putman for their valuable review and insights.  In
   addition, an extra special thank you to Jim Schaad for generating the
   examples in Appendix A.

Author's Address

   Russ Housley
   Vigil Security, LLC
   516 Dranesville Road
   Herndon, VA  20170
   US

   Email: housley@vigilsec.com







Housley                  Expires April 30, 2020                [Page 21]


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