path: root/doc/rfc/rfc6955.txt

Internet Engineering Task Force (IETF)                         J. Schaad
Request for Comments: 6955                       Soaring Hawk Consulting
Obsoletes: 2875                                        H. Prafullchandra
Category: Standards Track                                  HyTrust, Inc.
ISSN: 2070-1721                                                 May 2013


             Diffie-Hellman Proof-of-Possession Algorithms

Abstract

   This document describes two methods for producing an integrity check
   value from a Diffie-Hellman key pair and one method for producing an
   integrity check value from an Elliptic Curve key pair.  This behavior
   is needed for such operations as creating the signature of a Public-
   Key Cryptography Standards (PKCS) #10 Certification Request.  These
   algorithms are designed to provide a Proof-of-Possession of the
   private key and not to be a general purpose signing algorithm.

   This document obsoletes RFC 2875.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6955.

















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Copyright Notice

   Copyright (c) 2013 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

























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Table of Contents

   1. Introduction ....................................................3
      1.1. Changes since RFC 2875 .....................................4
      1.2. Requirements Terminology ...................................5
   2. Terminology .....................................................5
   3. Notation ........................................................5
   4. Static DH Proof-of-Possession Process ...........................6
      4.1. ASN.1 Encoding .............................................8
   5. Discrete Logarithm Signature ...................................11
      5.1. Expanding the Digest Value ................................11
      5.2. Signature Computation Algorithm ...........................12
      5.3. Signature Verification Algorithm ..........................13
      5.4. ASN.1 Encoding ............................................14
   6. Static ECDH Proof-of-Possession Process ........................16
      6.1. ASN.1 Encoding ............................................18
   7. Security Considerations ........................................20
   8. References .....................................................21
      8.1. Normative References ......................................21
      8.2. Informative References ....................................21
   Appendix A. ASN.1 Modules .........................................23
     A.1. 2008 ASN.1 Module ..........................................23
     A.2. 1988 ASN.1 Module ..........................................28
   Appendix B. Example of Static DH Proof-of-Possession ..............30
   Appendix C. Example of Discrete Log Signature .....................38

1.  Introduction

   Among the responsibilities of a Certification Authority (CA) in
   issuing certificates is a requirement that it verifies the identity
   for the entity to which it is issuing a certificate and that the
   private key for the public key to be placed in the certificate is in
   the possession of that entity.  The process of validating that the
   private key is held by the requester of the certificate is called
   Proof-of-Possession (POP).  Further details on why POP is important
   can be found in Appendix C of RFC 4211 [CRMF].

   This document is designed to deal with the problem of how to support
   POP for encryption-only keys.  PKCS #10 [RFC2986] and the Certificate
   Request Message Format (CRMF) [CRMF] both define syntaxes for
   Certification Requests.  However, while CRMF supports an alternative
   method to support POP for encryption-only keys, PKCS #10 does not.
   PKCS #10 assumes that the public key being requested for
   certification corresponds to an algorithm that is capable of
   producing a POP by a signature operation.  Diffie-Hellman (DH) and
   Elliptic Curve Diffie-Hellman (ECDH) are key agreement algorithms
   and, as such, cannot be directly used for signing or encryption.




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   This document describes a set of three POP algorithms.  Two methods
   use the key agreement process (one for DH and one for ECDH) to
   provide a shared secret as the basis of an integrity check value.
   For these methods, the value is constructed for a specific recipient/
   verifier by using a public key of that verifier.  The third method
   uses a modified signature algorithm (for DH).  This method allows for
   arbitrary verifiers.

   It should be noted that we did not create an algorithm that parallels
   the Elliptical Curve Digital Signature Algorithm (ECDSA) as was done
   for the Digital Signature Algorithm (DSA).  When using ECDH, the
   common practice is to use one of a set of predefined curves; each of
   these curves has been designed to be paired with one of the commonly
   used hash algorithms.  This differs in practice from the DH case
   where the common practice is to generate a set of group parameters,
   either on a single machine or for a given community, that are aligned
   to encryption algorithms rather than hash algorithms.  The
   implication is that, if a key has the ability to perform the modified
   DSA algorithm for ECDSA, it should be able to use the correct hash
   algorithm and perform the regular ECDSA signature algorithm with the
   correctly sized hash.

1.1.  Changes since RFC 2875

   The following changes have been made:

   o  The Static DH POP algorithm has been rewritten for
      parameterization of the hash algorithm and the Message
      Authentication Code (MAC) algorithm.

   o  New instances of the Static DH POP algorithm have been created
      using the Hashed Message Authentication Code (HMAC) paired with
      the SHA-224, SHA-256, SHA-384, and SHA-512 hash algorithms.
      However, the current SHA-1 algorithm remains identical.

   o  The Discrete Logarithm Signature algorithm has been rewritten for
      parameterization of the hash algorithm.

   o  New instances of the Discrete Logarithm Signature have been
      created for the SHA-224, SHA-256, SHA-384, and SHA-512 hash
      functions.  However, the current SHA-1 algorithm remains
      identical.

   o  A new Static ECDH POP algorithm has been added.

   o  New instances of the Static ECDH POP algorithm have been created
      using HMAC paired with the SHA-224, SHA-256, SHA-384, and SHA-512
      hash functions.



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1.2.  Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   When the words are in lower case they have their natural language
   meaning.

2.  Terminology

   The following definitions will be used in this document:

   DH certificate = a certificate whose SubjectPublicKey is a DH public
   value and is signed with any signature algorithm (e.g., RSA or DSA).

   ECDH certificate = a certificate whose SubjectPublicKey is an ECDH
   public value and is signed with any signature algorithm (e.g., RSA
   or ECDSA).

   Proof-of-Possession (POP) = a means that provides a method for a
   second party to perform an algorithm to establish with some degree of
   assurance that the first party does possess and has the ability to
   use a private key.  The reasoning behind doing POP can be found in
   Appendix C in [CRMF].

3.  Notation

   This section describes mathematical notations, conventions, and
   symbols used throughout this document.

     a | b          : Concatenation of a and b
     a ^ b          : a raised to the power of b
     a mod b        : a modulo b
     a / b          : a divided by b using integer division
     a * b          : a times b
                      Depending on context, multiplication may be within
                      an EC or normal multiplication

     KDF(a)         : Key Derivation Function producing a value from a
     MAC(a, b)      : Message Authentication Code function where
                      a is the key and b is the text
     LEFTMOST(a, b) : Return the b left most bits of a
     FLOOR(a)       : Return n where n is the largest integer such that
                      n <= a






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   Details on how to implement the HMAC version of a MAC function used
   in this document can be found in RFC 2104 [RFC2104], RFC 6234
   [RFC6234], and RFC 4231 [RFC4231].

4.  Static DH Proof-of-Possession Process

   The Static DH POP algorithm is set up to use a Key Derivation
   Function (KDF) and a MAC.  This algorithm requires that a common set
   of group parameters be used by both the creator and verifier of the
   POP value.

   The steps for creating a DH POP are:

   1.  An entity (E) chooses the group parameters for a DH key
       agreement.

       This is done simply by selecting the group parameters from a
       certificate for the recipient of the POP process.  A certificate
       with the correct group parameters has to be available.

       Let the common DH parameters be g and p; and let the DH key pair
       from the certificate be known as the recipient (R) key pair (Rpub
       and Rpriv).

       Rpub = g^x mod p (where x=Rpriv, the private DH value)

   2.  The entity generates a DH public/private key pair using the group
       parameters from step 1.

       For an entity (E):

       Epriv = DH private value = y
       Epub = DH public value = g^y mod p


















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   3.  The POP computation process will then consist of the following
       steps:

       (a)  The value to be signed (text) is obtained.  (For a PKCS #10
            object, the value is the DER-encoded
            certificationRequestInfo field represented as an octet
            string.)

       (b)  A shared DH secret is computed as follows:

            shared secret = ZZ = g^(x*y) mod p

            [This is done by E as Rpub^y and by the recipient as Epub^x,
            where Rpub is retrieved from the recipient's DH certificate
            (or is provided in the protocol) and Epub is retrieved from
            the Certification Request.]

       (c)  A temporary key K is derived from the shared secret ZZ as
            follows:

               K = KDF(LeadingInfo | ZZ | TrailingInfo)

               LeadingInfo ::= Subject Distinguished Name from
               recipient's certificate

               TrailingInfo ::= Issuer Distinguished Name from
               recipient's certificate

       (d)  Using the defined MAC function, compute MAC(K, text).

   The POP verification process requires the recipient to carry out
   steps (a) through (d) and then simply compare the result of step (d)
   with what it received as the signature component.  If they match,
   then the following can be concluded:

   (a)  The entity possesses the private key corresponding to the public
        key in the Certification Request because it needs the private
        key to calculate the shared secret; and

   (b)  Only the recipient that the entity sent the request to could
        actually verify the request because it would require its own
        private key to compute the same shared secret.  In the case
        where the recipient is a CA, this protects the entity from
        rogue CAs.







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4.1.  ASN.1 Encoding

   The algorithm outlined above allows for the use of an arbitrary hash
   function in computing the temporary key and the MAC algorithm.  In
   this specification, we define object identifiers for the SHA-1,
   SHA-224, SHA-256, SHA-384, and SHA-512 hash values and use HMAC for
   the MAC algorithm.  The ASN.1 structures associated with the Static
   DH POP algorithm are:

      DhSigStatic ::= SEQUENCE {
          issuerAndSerial IssuerAndSerialNumber OPTIONAL,
          hashValue       MessageDigest
      }

      sa-dhPop-static-sha1-hmac-sha1 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-dhPop-static-sha1-hmac-sha1
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }

      id-dh-sig-hmac-sha1 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 3
      }

      id-dhPop-static-sha1-hmac-sha1 OBJECT IDENTIFIER ::=
           id-dh-sig-hmac-sha1

      sa-dhPop-static-sha224-hmac-sha224 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-alg-dhPop-static-sha224-hmac-sha224
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-static-sha224-hmac-sha224 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 15
      }

      sa-dhPop-static-sha256-hmac-sha256 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-alg-dhPop-static-sha256-hmac-sha256
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }






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      id-alg-dhPop-static-sha256-hmac-sha256 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 16
      }

      sa-dhPop-static-sha384-hmac-sha384 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-alg-dhPop-static-sha384-hmac-sha384
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-static-sha384-hmac-sha384 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 17
      }

      sa-dhPop-static-sha512-hmac-sha512 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-alg-dhPop-static-sha512-hmac-sha512
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-static-sha512-hmac-sha512 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 18
      }

   In the above ASN.1, the following items are defined:

   DhSigStatic
      This ASN.1 type structure holds the information describing the
      signature.  The structure has the following fields:

      issuerAndSerial
         This field contains the issuer name and serial number of the
         certificate from which the public key was obtained.  The
         issuerAndSerial field is omitted if the public key did not come
         from a certificate.

      hashValue
         This field contains the result of the MAC operation in
         step 3(d) (Section 4).

   sa-dhPop-static-sha1-hmac-sha1
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing a signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.




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   id-dhPop-static-sha1-hmac-sha1
      This OID identifies the Static DH POP algorithm that uses SHA-1 as
      the KDF and HMAC-SHA1 as the MAC function.  The new OID was
      created for naming consistency with the other OIDs defined here.
      The value of the OID is the same value as id-dh-sig-hmac-sha1,
      which was defined in the previous version of this document
      [RFC2875].

   sa-dhPop-static-sha224-hmac-sha224
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.

   id-dhPop-static-sha224-hmac-sha224
      This OID identifies the Static DH POP algorithm that uses SHA-224
      as the KDF and HMAC-SHA224 as the MAC function.

   sa-dhPop-static-sha256-hmac-sha256
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.

   id-dhPop-static-sha256-hmac-sha256
      This OID identifies the Static DH POP algorithm that uses SHA-256
      as the KDF and HMAC-SHA256 as the MAC function.

   sa-dhPop-static-sha384-hmac-sha384
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.

   id-dhPop-static-sha384-hmac-sha384
      This OID identifies the Static DH POP algorithm that uses SHA-384
      as the KDF and HMAC-SHA384 as the MAC function.

   sa-dhPop-static-sha512-hmac-sha512
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.

   id-dhPop-static-sha512-hmac-sha512
      This OID identifies the Static DH POP algorithm that uses SHA-512
      as the KDF and HMAC-SHA512 as the MAC function.




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5.  Discrete Logarithm Signature

   When a single set of parameters is used for a large group of keys,
   the chance that a collision will occur in the set of keys, either by
   accident or design, increases as the number of keys used increases.
   A large number of keys from a single parameter set also encourages
   the use of brute force methods of attack, as the entire set of keys
   in the parameters can be attacked in a single operation rather than
   having to attack each key parameter set individually.

   For this reason, we need to create a POP for DH keys that does not
   require the use of a common set of parameters.

   This POP algorithm is based on DSA, but we have removed the
   restrictions dealing with the hash and key sizes imposed by the
   [FIPS-186-3] standard.  The use of this method does impose some
   additional restrictions on the set of keys that may be used; however,
   if the key-generation algorithm documented in [RFC2631] is used, the
   required restrictions are met.  The additional restrictions are the
   requirement for the existence of a q parameter.  Adding the q
   parameter is generally accepted as a good practice, as it allows for
   checking of small subgroup attacks.

   The following definitions are used in the rest of this section:

   p is a large prime
   g = h^((p-1)/q) mod p,
   where h is any integer 1 < h < p-1 such that h^((p-1)/q) mod p > 1
   (g has order q mod p)
   q is a large prime
   j is a large integer such that p = q*j + 1
   x is a randomly or pseudo-randomly generated integer with 1 < x < q
   y = g^x mod p
   HASH is a hash function such that
   b = the output size of HASH in bits

   Note: These definitions match the ones in [RFC2631].

5.1.  Expanding the Digest Value

   Besides the addition of a q parameter, [FIPS-186-3] also imposes size
   restrictions on the parameters.  The length of q must be 160 bits
   (matching the output length of the SHA-1 digest algorithm), and the
   length of p must be 1024 bits.  The size restriction on p is
   eliminated in this document, but the size restriction on q is
   replaced with the requirement that q must be at least b bits in
   length.  (If the hash function is SHA-1, then b=160 bits and the size
   restriction on b is identical with that in [FIPS-186-3].)  Given that



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   there is not a random length-hashing algorithm, a hash value of the
   message will need to be derived such that the hash is in the range
   from 0 to q-1.  If the length of q is greater than b, then a method
   must be provided to expand the hash.

   The method for expanding the digest value used in this section does
   not provide any additional security beyond the b bits provided by the
   hash algorithm.  For this reason, the hash algorithm should be the
   largest size possible to match q.  The value being signed is
   increased mainly to enhance the difficulty of reversing the signature
   process.

   This algorithm produces m, the value to be signed.

   Let L = the size of q (i.e., 2^L <= q < 2^(L+1)).
   Let M be the original message to be signed.
   Let b be the length of HASH output.

   1.  Compute d = HASH(M), the digest of the original message.

   2.  If L == b, then m = d.

   3.  If L > b, then follow steps (a) through (d) below.

       (a)  Set n = FLOOR(L / b)

       (b)  Set m = d, the initial computed digest value

       (c)  For i = 0 to n - 1
            m = m | HASH(m)

       (d)  m = LEFTMOST(m, L-1)

   Thus, the final result of the process meets the criteria that
   0 <= m < q.

5.2.  Signature Computation Algorithm

   The signature algorithm produces the pair of values (r, s), which is
   the signature.  The signature is computed as follows:

   Given m, the value to be signed, as well as the parameters defined
   earlier in Section 5:

   1.  Generate a random or pseudo-random integer k, such that
       0 < k-1 < q.

   2.  Compute r = (g^k mod p) mod q.



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   3.  If r is zero, repeat from step 1.

   4.  Compute s = ((k^-1) * (m + x*r)) mod q.

   5.  If s is zero, repeat from step 1.

5.3.  Signature Verification Algorithm

   The signature verification process is far more complicated than is
   normal for DSA, as some assumptions about the validity of parameters
   cannot be taken for granted.

   Given a value m to be validated, the signature value pair (r, s) and
   the parameters for the key:

   1.  Perform a strong verification that p is a prime number.

   2.  Perform a strong verification that q is a prime number.

   3.  Verify that q is a factor of p-1; if any of the above checks
       fail, then the signature cannot be verified and must be
       considered a failure.

   4.  Verify that r and s are in the range [1, q-1].

   5.  Compute w = (s^-1) mod q.

   6.  Compute u1 = m*w mod q.

   7.  Compute u2 = r*w mod q.

   8.  Compute v = ((g^u1 * y^u2) mod p) mod q.

   9.  Compare v and r; if they are the same, then the signature
       verified correctly.
















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5.4.  ASN.1 Encoding

   The signature algorithm is parameterized by the hash algorithm.  The
   ASN.1 structures associated with the Discrete Logarithm Signature
   algorithm are:

      sa-dhPop-SHA1 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dh-pop
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha1 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha1 OBJECT IDENTIFIER ::= id-alg-dh-pop

      id-alg-dh-pop OBJECT IDENTIFIER ::= { id-pkix id-alg(6) 4 }

      sa-dhPop-sha224 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dhPop-sha224
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha224 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha224 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 5
      }

      sa-dhPop-sha256 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dhPop-sha256
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha256 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha256 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 6
      }










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      sa-dhPop-sha384 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dhPop-sha384
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha384 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha384 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 7
      }

      sa-dhPop-sha512 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dhPop-sha512
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha512 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha512 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 8
      }

   In the above ASN.1, the following items are defined:

   sa-dhPop-sha1
      A SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DSA-Sig-Value represents the signature value, and the structure
      DomainParameters SHOULD be omitted in the signature but MUST be
      present in the associated key request.

   id-alg-dhPop-sha1
      This OID identifies the Discrete Logarithm Signature using SHA-1
      as the hash algorithm.  The new OID was created for naming
      consistency with the others defined here.  The value of the OID is
      the same as id-alg-dh-pop, which was defined in the previous
      version of this document [RFC2875].

   sa-dhPop-sha224
      A SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DSA-Sig-Value represents the signature value, and the structure
      DomainParameters SHOULD be omitted in the signature but MUST be
      present in the associated key request.





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   id-alg-dhPop-sha224
      This OID identifies the Discrete Logarithm Signature using SHA-224
      as the hash algorithm.

   sa-dhPop-sha256
      A SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DSA-Sig-Value represents the signature value, and the structure
      DomainParameters SHOULD be omitted in the signature but MUST be
      present in the associated key request.

   id-alg-dhPop-sha256
      This OID identifies the Discrete Logarithm Signature using SHA-256
      as the hash algorithm.

   sa-dhPop-sha384
      A SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DSA-Sig-Value represents the signature value, and the structure
      DomainParameters SHOULD be omitted in the signature but MUST be
      present in the associated key request.

   id-alg-dhPop-sha384
      This OID identifies the Discrete Logarithm Signature using SHA-384
      as the hash algorithm.

   sa-dhPop-sha512
      A SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DSA-Sig-Value represents the signature value, and the structure
      DomainParameters SHOULD be omitted in the signature but MUST be
      present in the associated key request.

   id-alg-dhPop-sha512
      This OID identifies the Discrete Logarithm Signature using SHA-512
      as the hash algorithm.

6.  Static ECDH Proof-of-Possession Process

   The Static ECDH POP algorithm is set up to use a KDF and a MAC.  This
   algorithm requires that a common set of group parameters be used by
   both the creator and the verifier of the POP value.  Full details of
   how Elliptic Curve Cryptography (ECC) works can be found in RFC 6090
   [RFC6090].







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   The steps for creating an ECDH POP are:

   1.  An entity (E) chooses the group parameters for an ECDH key
       agreement.

       This is done simply by selecting the group parameters from a
       certificate for the recipient of the POP process.  A certificate
       with the correct group parameters has to be available.

       The ECDH parameters can be identified either by a named group or
       by a set of curve parameters.  Section 2.3.5 of RFC 3279
       [RFC3279] documents how the parameters are encoded for PKIX
       certificates.  For PKIX-based applications, the parameters will
       almost always be defined by a named group.  Designate G as the
       group from the ECDH parameters.  Let the ECDH key pair associated
       with the certificate be known as the recipient key pair (Rpub
       and Rpriv).

       Rpub = Rpriv * G

   2.  The entity generates an ECDH public/private key pair using the
       parameters from step 1.

       For an entity (E):

       Epriv = entity private value
       Epub = ECDH public point = Epriv * G

   3.  The POP computation process will then consist of the following
       steps:

       (a)  The value to be signed (text) is obtained.  (For a PKCS #10
            object, the value is the DER-encoded
            certificationRequestInfo field represented as an octet
            string.)

       (b)  A shared ECDH secret is computed as follows:

            shared secret point (x, y) = Epriv * Rpub = Rpriv * Epub

            shared secret value ZZ is the x coordinate of the computed
            point









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       (c)  A temporary key K is derived from the shared secret ZZ as
            follows:

            K = KDF(LeadingInfo | ZZ | TrailingInfo)

            LeadingInfo ::= Subject Distinguished Name from certificate
            TrailingInfo ::= Issuer Distinguished Name from certificate

       (d)  Compute MAC(K, text).

   The POP verification process requires the recipient to carry out
   steps (a) through (d) and then simply compare the result of step (d)
   with what it received as the signature component.  If they match,
   then the following can be concluded:

   (a)  The entity possesses the private key corresponding to the public
        key in the Certification Request because it needed the private
        key to calculate the shared secret; and

   (b)  Only the recipient that the entity sent the request to could
        actually verify the request because it would require its own
        private key to compute the same shared secret.  In the case
        where the recipient is a CA, this protects the entity from
        rogue CAs.

6.1.  ASN.1 Encoding

   The algorithm outlined above allows for the use of an arbitrary hash
   function in computing the temporary key and the MAC value.  In this
   specification, we define object identifiers for the SHA-1, SHA-224,
   SHA-256, SHA-384, and SHA-512 hash values.  The ASN.1 structures
   associated with the Static ECDH POP algorithm are:

      id-alg-ecdhPop-static-sha224-hmac-sha224 OBJECT IDENTIFIER ::= {
         id-pkix id-alg(6) 25
      }

      sa-ecdhPop-sha224-hmac-sha224 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-ecdhPop-static-sha224-hmac-sha224
         VALUE DhSigStatic
         PARAMS ARE absent
         PUBLIC-KEYS { pk-ec }
      }








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      id-alg-ecdhPop-static-sha256-hmac-sha256 OBJECT IDENTIFIER ::= {
         id-pkix id-alg(6) 26
      }

      sa-ecdhPop-sha256-hmac-sha256 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-ecdhPop-static-sha256-hmac-sha256
         VALUE DhSigStatic
         PARAMS ARE absent
         PUBLIC-KEYS { pk-ec }
      }

      id-alg-ecdhPop-static-sha384-hmac-sha384 OBJECT IDENTIFIER ::= {
         id-pkix id-alg(6) 27
      }

      sa-ecdhPop-sha384-hmac-sha384 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-ecdhPop-static-sha384-hmac-sha384
         VALUE DhSigStatic
         PARAMS ARE absent
         PUBLIC-KEYS { pk-ec }
      }

      id-alg-ecdhPop-static-sha512-hmac-sha512 OBJECT IDENTIFIER ::= {
         id-pkix id-alg(6) 28
      }

      sa-ecdhPop-sha512-hmac-sha512 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-ecdhPop-static-sha512-hmac-sha512
         VALUE DhSigStatic
         PARAMS ARE absent
         PUBLIC-KEYS { pk-ec }
      }

   These items reuse the DhSigStatic structure defined in Section 4.
   When used with these algorithms, the value to be placed in the field
   hashValue is that computed in step 3(d) (Section 6).  In the above
   ASN.1, the following items are defined:

   sa-ecdhPop-static-sha224-hmac-sha224
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.

   id-ecdhPop-static-sha224-hmac-sha224
      This OID identifies the Static ECDH POP algorithm that uses
      SHA-224 as the KDF and HMAC-SHA224 as the MAC function.




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   sa-ecdhPop-static-sha256-hmac-sha256
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.

   id-ecdhPop-static-sha256-hmac-sha256
      This OID identifies the Static ECDH POP algorithm that uses
      SHA-256 as the KDF and HMAC-SHA256 as the MAC function.

   sa-ecdhPop-static-sha384-hmac-sha384
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.

   id-ecdhPop-static-sha384-hmac-sha384
      This OID identifies the Static ECDH POP algorithm that uses
      SHA-384 as the KDF and HMAC-SHA384 as the MAC function.

   sa-ecdhPop-static-sha512-hmac-sha512
      An ASN.1 SIGNATURE-ALGORITHM object that associates together the
      information describing this signature algorithm.  The structure
      DhSigStatic represents the signature value, and the parameters
      MUST be absent.

   id-ecdhPop-static-sha512-hmac-sha512
      This OID identifies the Static ECDH POP algorithm that uses
      SHA-512 as the KDF and HMAC-SHA512 as the MAC function.

7.  Security Considerations

   None of the algorithms defined in this document are meant for use in
   general purpose situations.  These algorithms are designed and
   purposed solely for use in doing POP with PKCS #10 and CRMF
   constructs.

   In the Static DH POP and Static ECDH POP algorithms, an appropriate
   value can be produced by either party.  Thus, these algorithms only
   provide integrity and not origination service.  The Discrete
   Logarithm Signature algorithm provides both integrity checking and
   origination checking.

   All the security in this system is provided by the secrecy of the
   private keying material.  If either sender or recipient private keys
   are disclosed, all messages sent or received using those keys are
   compromised.  Similarly, the loss of a private key results in an
   inability to read messages sent using that key.



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   Selection of parameters can be of paramount importance.  In the
   selection of parameters, one must take into account the community/
   group of entities that one wishes to be able to communicate with.  In
   choosing a set of parameters, one must also be sure to avoid small
   groups.  [FIPS-186-3] Appendixes A and B.2 contain information on the
   selection of parameters for DH.  Section 10 of [RFC6090] contains
   information on the selection of parameters for ECC.  The practices
   outlined in these documents will lead to better selection of
   parameters.

8.  References

8.1.  Normative References

   [RFC2104]     Krawczyk, H., Bellare, M., and R. Canetti, "HMAC:
                 Keyed-Hashing for Message Authentication", RFC 2104,
                 February 1997.

   [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2631]     Rescorla, E., "Diffie-Hellman Key Agreement Method",
                 RFC 2631, June 1999.

   [RFC2986]     Nystrom, M. and B. Kaliski, "PKCS #10: Certification
                 Request Syntax Specification Version 1.7", RFC 2986,
                 November 2000.

   [RFC4231]     Nystrom, M., "Identifiers and Test Vectors for HMAC-
                 SHA-224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",
                 RFC 4231, December 2005.

   [RFC6234]     Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
                 (SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011.

8.2.  Informative References

   [CRMF]        Schaad, J., "Internet X.509 Public Key Infrastructure
                 Certificate Request Message Format (CRMF)", RFC 4211,
                 September 2005.

   [FIPS-186-3]  National Institute of Standards and Technology,
                 "Digital Signature Standard (DSS)", Federal Information
                 Processing Standards Publication 186-3, June 2009,
                 <http://www.nist.gov/>.

   [RFC2875]     Prafullchandra, H. and J. Schaad, "Diffie-Hellman
                 Proof-of-Possession Algorithms", RFC 2875, July 2000.



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   [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, April 2002.

   [RFC5912]     Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
                 Public Key Infrastructure Using X.509 (PKIX)",
                 RFC 5912, June 2010.

   [RFC6090]     McGrew, D., Igoe, K., and M. Salter, "Fundamental
                 Elliptic Curve Cryptography Algorithms", RFC 6090,
                 February 2011.







































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Appendix A.  ASN.1 Modules

A.1.  2008 ASN.1 Module

   This appendix contains an ASN.1 module that is conformant with the
   2008 version of ASN.1.  This module references the object classes
   defined by [RFC5912] to more completely describe all of the
   associations between the elements defined in this document.  Where a
   difference exists between the module in this section and the 1988
   module, the 2008 module is the definitive module.

   DH-Sign
      { iso(1) identified-organization(3) dod(6) internet(1)
        security(5) mechanisms(5) pkix(7) id-mod(0)
        id-mod-dhSign-2012-08(80) }
   DEFINITIONS IMPLICIT TAGS ::=

   BEGIN
   -- EXPORTS ALL
   -- The types and values defined in this module are exported for use
   -- in the other ASN.1 modules.  Other applications may use them
   -- for their own purposes.

   IMPORTS
      SIGNATURE-ALGORITHM
      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) }

      IssuerAndSerialNumber, MessageDigest
      FROM CryptographicMessageSyntax-2010
         { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
           pkcs-9(9) smime(16) modules(0) id-mod-cms-2009(58) }

      DSA-Sig-Value, DomainParameters, ECDSA-Sig-Value,
      mda-sha1, mda-sha224, mda-sha256, mda-sha384, mda-sha512,
      pk-dh, pk-ec
      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) }

      id-pkix
      FROM PKIX1Explicit-2009
         { iso(1) identified-organization(3) dod(6) internet(1)
           security(5) mechanisms(5) pkix(7) id-mod(0)
           id-mod-pkix1-explicit-02(51) };



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      DhSigStatic ::= SEQUENCE {
          issuerAndSerial IssuerAndSerialNumber OPTIONAL,
          hashValue       MessageDigest
      }

      sa-dhPop-static-sha1-hmac-sha1 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-dhPop-static-sha1-hmac-sha1
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }

      id-dh-sig-hmac-sha1 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 3
      }

      id-dhPop-static-sha1-hmac-sha1 OBJECT IDENTIFIER ::=
           id-dh-sig-hmac-sha1

      sa-dhPop-static-sha224-hmac-sha224 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-alg-dhPop-static-sha224-hmac-sha224
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-static-sha224-hmac-sha224 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 15
      }

      sa-dhPop-static-sha256-hmac-sha256 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-alg-dhPop-static-sha256-hmac-sha256
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-static-sha256-hmac-sha256 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 16
      }

      sa-dhPop-static-sha384-hmac-sha384 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-alg-dhPop-static-sha384-hmac-sha384
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }




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      id-alg-dhPop-static-sha384-hmac-sha384 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 17
      }

      sa-dhPop-static-sha512-hmac-sha512 SIGNATURE-ALGORITHM ::= {
           IDENTIFIER id-alg-dhPop-static-sha512-hmac-sha512
           VALUE DhSigStatic
           PARAMS ARE absent
           PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-static-sha512-hmac-sha512 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 18
      }

      sa-dhPop-SHA1 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dh-pop
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha1 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha1 OBJECT IDENTIFIER ::= id-alg-dh-pop

      id-alg-dh-pop OBJECT IDENTIFIER ::= { id-pkix id-alg(6) 4 }

      sa-dhPop-sha224 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dhPop-sha224
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha224 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha224 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 5
      }

      sa-dhPop-sha256 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dhPop-sha256
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha256 }
         PUBLIC-KEYS { pk-dh }
      }





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      id-alg-dhPop-sha256 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 6
      }

      sa-dhPop-sha384 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dhPop-sha384
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha384 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha384 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 7
      }

      sa-dhPop-sha512 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-dhPop-sha512
         VALUE DSA-Sig-Value
         PARAMS TYPE DomainParameters ARE preferredAbsent
         HASHES { mda-sha512 }
         PUBLIC-KEYS { pk-dh }
      }

      id-alg-dhPop-sha512 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 8
      }

      id-alg-ecdhPop-static-sha224-hmac-sha224 OBJECT IDENTIFIER ::= {
         id-pkix id-alg(6) 25
      }

      sa-ecdhPop-sha224-hmac-sha224 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-ecdhPop-static-sha224-hmac-sha224
         VALUE DhSigStatic
         PARAMS ARE absent
         PUBLIC-KEYS { pk-ec }
      }

      id-alg-ecdhPop-static-sha256-hmac-sha256 OBJECT IDENTIFIER ::= {
         id-pkix id-alg(6) 26
      }









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      sa-ecdhPop-sha256-hmac-sha256 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-ecdhPop-static-sha256-hmac-sha256
         VALUE DhSigStatic
         PARAMS ARE absent
         PUBLIC-KEYS { pk-ec }
      }

      id-alg-ecdhPop-static-sha384-hmac-sha384 OBJECT IDENTIFIER ::= {
         id-pkix id-alg(6) 27
      }

      sa-ecdhPop-sha384-hmac-sha384 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-ecdhPop-static-sha384-hmac-sha384
         VALUE DhSigStatic
         PARAMS ARE absent
         PUBLIC-KEYS { pk-ec }
      }

      id-alg-ecdhPop-static-sha512-hmac-sha512 OBJECT IDENTIFIER ::= {
         id-pkix id-alg(6) 28
      }

      sa-ecdhPop-sha512-hmac-sha512 SIGNATURE-ALGORITHM ::= {
         IDENTIFIER id-alg-ecdhPop-static-sha512-hmac-sha512
         VALUE DhSigStatic
         PARAMS ARE absent
         PUBLIC-KEYS { pk-ec }
      }

   END





















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A.2.  1988 ASN.1 Module

   This appendix contains an ASN.1 module that is conformant with the
   1988 version of ASN.1, which represents an informational version of
   the ASN.1 module for this document.  Where a difference exists
   between the module in this section and the 2008 module, the 2008
   module is the definitive module.

   DH-Sign
      { iso(1) identified-organization(3) dod(6) internet(1)
        security(5) mechanisms(5) pkix(7) id-mod(0)
        id-mod-dhSign-2012-88(79) }
   DEFINITIONS IMPLICIT TAGS ::=

   BEGIN
   -- EXPORTS ALL
   -- The types and values defined in this module are exported for use
   -- in the other ASN.1 modules.  Other applications may use them
   -- for their own purposes.

   IMPORTS
      IssuerAndSerialNumber, MessageDigest
      FROM CryptographicMessageSyntax2004
         { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
           pkcs-9(9) smime(16) modules(0) cms-2004(24) }

      id-pkix
      FROM PKIX1Explicit88
         { iso(1) identified-organization(3) dod(6) internet(1)
           security(5) mechanisms(5) pkix(7) id-mod(0)
           id-pkix1-explicit(18) }

      Dss-Sig-Value, DomainParameters
      FROM PKIX1Algorithms88
         { iso(1) identified-organization(3) dod(6) internet(1)
           security(5) mechanisms(5) pkix(7) id-mod(0)
           id-mod-pkix1-algorithms(17) };

      id-dh-sig-hmac-sha1 OBJECT IDENTIFIER ::= {id-pkix id-alg(6) 3}

      DhSigStatic ::= SEQUENCE {
          issuerAndSerial IssuerAndSerialNumber OPTIONAL,
          hashValue       MessageDigest
      }

      id-alg-dh-pop OBJECT IDENTIFIER ::= { id-pkix id-alg(6) 4 }





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      id-dhPop-static-sha1-hmac-sha1 OBJECT IDENTIFIER ::=
           id-dh-sig-hmac-sha1

      id-alg-dhPop-static-sha224-hmac-sha224 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 15 }

      id-alg-dhPop-static-sha256-hmac-sha256 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 16 }

      id-alg-dhPop-static-sha384-hmac-sha384 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 17 }

      id-alg-dhPop-static-sha512-hmac-sha512 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 18 }


      id-alg-dhPop-sha1 OBJECT IDENTIFIER ::= id-alg-dh-pop

      id-alg-dhPop-sha224 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 5 }

      id-alg-dhPop-sha256 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 6 }

      id-alg-dhPop-sha384 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 7 }

      id-alg-dhPop-sha512 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 8 }


      id-alg-ecdhPop-static-sha224-hmac-sha224 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 25 }

      id-alg-ecdhPop-static-sha256-hmac-sha256 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 26 }

      id-alg-ecdhPop-static-sha384-hmac-sha384 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 27 }

      id-alg-ecdhPop-static-sha512-hmac-sha512 OBJECT IDENTIFIER ::= {
           id-pkix id-alg(6) 28 }

   END







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Appendix B.  Example of Static DH Proof-of-Possession

   The following example follows the steps described earlier in
   Section 4.

   Step 1.  Establishing common DH parameters: Assume the parameters are
   as in the DER-encoded certificate.  The certificate contains a DH
   public key signed by a CA with a DSA signing key.

  0 30 939: SEQUENCE {
  4 30 872:   SEQUENCE {
  8 A0   3:     [0] {
 10 02   1:       INTEGER 2
          :       }
 13 02   6:     INTEGER
          :       00 DA 39 B6 E2 CB
 21 30  11:     SEQUENCE {
 23 06   7:       OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
 32 05   0:       NULL
          :       }
 34 30  72:     SEQUENCE {
 36 31  11:       SET {
 38 30   9:         SEQUENCE {
 40 06   3:           OBJECT IDENTIFIER countryName (2 5 4 6)
 45 13   2:           PrintableString 'US'
          :           }
          :         }
 49 31  17:       SET {
 51 30  15:         SEQUENCE {
 53 06   3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
 58 13   8:           PrintableString 'XETI Inc'
          :           }
          :         }
 68 31  16:       SET {
 70 30  14:         SEQUENCE {
 72 06   3:           OBJECT IDENTIFIER organizationalUnitName (2 5 4
                                11)
 77 13   7:           PrintableString 'Testing'
          :           }
          :         }
 86 31  20:       SET {
 88 30  18:         SEQUENCE {
 90 06   3:           OBJECT IDENTIFIER commonName (2 5 4 3)
 95 13  11:           PrintableString 'Root DSA CA'
          :           }
          :         }
          :       }




Schaad & Prafullchandra      Standards Track                   [Page 30]
^L
RFC 6955                    DH POP Algorithms                   May 2013


108 30  30:     SEQUENCE {
110 17  13:       UTCTime '990914010557Z'
125 17  13:       UTCTime '991113010557Z'
          :       }
140 30  70:     SEQUENCE {
142 31  11:       SET {
144 30   9:         SEQUENCE {
146 06   3:           OBJECT IDENTIFIER countryName (2 5 4 6)
151 13   2:           PrintableString 'US'
          :           }
          :         }
155 31  17:       SET {
157 30  15:         SEQUENCE {
159 06   3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
164 13   8:           PrintableString 'XETI Inc'
          :           }
          :         }
174 31  16:       SET {
176 30  14:         SEQUENCE {
178 06   3:           OBJECT IDENTIFIER organizationalUnitName (2 5 4
                                11)
183 13   7:           PrintableString 'Testing'
          :           }
          :         }
192 31  18:       SET {
194 30  16:         SEQUENCE {
196 06   3:           OBJECT IDENTIFIER commonName (2 5 4 3)
201 13   9:           PrintableString 'DH TestCA'
          :           }
          :         }
          :       }
212 30 577:     SEQUENCE {
216 30 438:       SEQUENCE {
220 06   7:         OBJECT IDENTIFIER dhPublicKey (1 2 840 10046 2 1)
229 30 425:         SEQUENCE {
233 02 129:           INTEGER
          :             00 94 84 E0 45 6C 7F 69 51 62 3E 56 80 7C 68 E7
          :             C5 A9 9E 9E 74 74 94 ED 90 8C 1D C4 E1 4A 14 82
          :             F5 D2 94 0C 19 E3 B9 10 BB 11 B9 E5 A5 FB 8E 21
          :             51 63 02 86 AA 06 B8 21 36 B6 7F 36 DF D1 D6 68
          :             5B 79 7C 1D 5A 14 75 1F 6A 93 75 93 CE BB 97 72
          :             8A F0 0F 23 9D 47 F6 D4 B3 C7 F0 F4 E6 F6 2B C2
          :             32 E1 89 67 BE 7E 06 AE F8 D0 01 6B 8B 2A F5 02
          :             D7 B6 A8 63 94 83 B0 1B 31 7D 52 1A DE E5 03 85
          :             27






Schaad & Prafullchandra      Standards Track                   [Page 31]
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RFC 6955                    DH POP Algorithms                   May 2013


365 02 128:           INTEGER
          :             26 A6 32 2C 5A 2B D4 33 2B 5C DC 06 87 53 3F 90
          :             06 61 50 38 3E D2 B9 7D 81 1C 12 10 C5 0C 53 D4
          :             64 D1 8E 30 07 08 8C DD 3F 0A 2F 2C D6 1B 7F 57
          :             86 D0 DA BB 6E 36 2A 18 E8 D3 BC 70 31 7A 48 B6
          :             4E 18 6E DD 1F 22 06 EB 3F EA D4 41 69 D9 9B DE
          :             47 95 7A 72 91 D2 09 7F 49 5C 3B 03 33 51 C8 F1
          :             39 9A FF 04 D5 6E 7E 94 3D 03 B8 F6 31 15 26 48
          :             95 A8 5C DE 47 88 B4 69 3A 00 A7 86 9E DA D1 CD
496 02  33:           INTEGER
          :             00 E8 72 FA 96 F0 11 40 F5 F2 DC FD 3B 5D 78 94
          :             B1 85 01 E5 69 37 21 F7 25 B9 BA 71 4A FC 60 30
          :             FB
531 02  97:           INTEGER
          :             00 A3 91 01 C0 A8 6E A4 4D A0 56 FC 6C FE 1F A7
          :             B0 CD 0F 94 87 0C 25 BE 97 76 8D EB E5 A4 09 5D
          :             AB 83 CD 80 0B 35 67 7F 0C 8E A7 31 98 32 85 39
          :             40 9D 11 98 D8 DE B8 7F 86 9B AF 8D 67 3D B6 76
          :             B4 61 2F 21 E1 4B 0E 68 FF 53 3E 87 DD D8 71 56
          :             68 47 DC F7 20 63 4B 3C 5F 78 71 83 E6 70 9E E2
          :             92
630 30  26:           SEQUENCE {
632 03  21:             BIT STRING 0 unused bits
          :             1C D5 3A 0D 17 82 6D 0A 81 75 81 46 10 8E 3E DB
          :             09 E4 98 34
655 02   1:             INTEGER 55
          :             }
          :           }
          :         }
658 03 132:       BIT STRING 0 unused bits
          :         02 81 80 5F CF 39 AD 62 CF 49 8E D1 CE 66 E2 B1
          :         E6 A7 01 4D 05 C2 77 C8 92 52 42 A9 05 A4 DB E0
          :         46 79 50 A3 FC 99 3D 3D A6 9B A9 AD BC 62 1C 69
          :         B7 11 A1 C0 2A F1 85 28 F7 68 FE D6 8F 31 56 22
          :         4D 0A 11 6E 72 3A 02 AF 0E 27 AA F9 ED CE 05 EF
          :         D8 59 92 C0 18 D7 69 6E BD 70 B6 21 D1 77 39 21
          :         E1 AF 7A 3A CF 20 0A B4 2C 69 5F CF 79 67 20 31
          :         4D F2 C6 ED 23 BF C4 BB 1E D1 71 40 2C 07 D6 F0
          :         8F C5 1A
          :       }
793 A3  85:     [3] {
795 30  83:       SEQUENCE {
797 30  29:         SEQUENCE {
799 06   3:           OBJECT IDENTIFIER subjectKeyIdentifier (2 5 29 14)
804 04  22:           OCTET STRING
          :             04 14 80 DF 59 88 BF EB 17 E1 AD 5E C6 40 A3 42
          :             E5 AC D3 B4 88 78
          :           }



Schaad & Prafullchandra      Standards Track                   [Page 32]
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RFC 6955                    DH POP Algorithms                   May 2013


828 30  34:         SEQUENCE {
830 06   3:           OBJECT IDENTIFIER authorityKeyIdentifier (2 5 29
35)
835 01   1:           BOOLEAN TRUE
838 04  24:           OCTET STRING
          :             30 16 80 14 6A 23 37 55 B9 FD 81 EA E8 4E D3 C9
          :             B7 09 E5 7B 06 E3 68 AA
          :           }
864 30  14:         SEQUENCE {
866 06   3:           OBJECT IDENTIFIER keyUsage (2 5 29 15)
871 01   1:           BOOLEAN TRUE
874 04   4:           OCTET STRING
          :             03 02 03 08
          :           }
          :         }
          :       }
          :     }
880 30  11:   SEQUENCE {
882 06   7:     OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
891 05   0:     NULL
          :     }
893 03  48:   BIT STRING 0 unused bits
          :     30 2D 02 14 7C 6D D2 CA 1E 32 D1 30 2E 29 66 BC
          :     06 8B 60 C7 61 16 3B CA 02 15 00 8A 18 DD C1 83
          :     58 29 A2 8A 67 64 03 92 AB 02 CE 00 B5 94 6A
          :   }

   Step 2.  End entity/user generates a DH key pair using the parameters
   from the CA certificate.

   End entity DH public key:

      Y: 13 63 A1 85 04 8C 46 A8 88 EB F4 5E A8 93 74 AE
         FD AE 9E 96 27 12 65 C4 4C 07 06 3E 18 FE 94 B8
         A8 79 48 BD 2E 34 B6 47 CA 04 30 A1 EC 33 FD 1A
         0B 2D 9E 50 C9 78 0F AE 6A EC B5 6B 6A BE B2 5C
         DA B2 9F 78 2C B9 77 E2 79 2B 25 BF 2E 0B 59 4A
         93 4B F8 B3 EC 81 34 AE 97 47 52 E0 A8 29 98 EC
         D1 B0 CA 2B 6F 7A 8B DB 4E 8D A5 15 7E 7E AF 33
         62 09 9E 0F 11 44 8C C1 8D A2 11 9E 53 EF B2 E8

   End entity DH private key:

      X: 32 CC BD B4 B7 7C 44 26 BB 3C 83 42 6E 7D 1B 00
         86 35 09 71 07 A0 A4 76 B8 DB 5F EC 00 CE 6F C3






Schaad & Prafullchandra      Standards Track                   [Page 33]
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RFC 6955                    DH POP Algorithms                   May 2013


   Step 3.  Compute the shared secret ZZ.

     56 b6 01 39 42 8e 09 16 30 b0 31 4d 12 90 af 03
     c7 92 65 c2 9c ba 88 bb 0a d5 94 02 ed 6f 54 cb
     22 e5 94 b4 d6 60 72 bc f6 a5 2b 18 8d df 28 72
     ac e0 41 dd 3b 03 2a 12 9e 5d bd 72 a0 1e fb 6b
     ee c5 b2 16 59 ee 12 00 3b c8 e0 cb c5 08 8e 2d
     40 5f 2d 37 62 8c 4f bb 49 76 69 3c 9e fc 2c f7
     f9 50 c1 b9 f7 01 32 4c 96 b9 c3 56 c0 2c 1b 77
     3f 2f 36 e8 22 c8 2e 07 76 d0 4f 7f aa d5 c0 59

   Step 4.  Compute K and the signature.

   LeadingInfo: DER-encoded Subject/Requester Distinguished Name (DN),
   as in the generated Certificate Signing Request

        30 46 31 0B 30 09 06 03 55 04 06 13 02 55 53 31
        11 30 0F 06 03 55 04 0A 13 08 58 45 54 49 20 49
        6E 63 31 10 30 0E 06 03 55 04 0B 13 07 54 65 73
        74 69 6E 67 31 12 30 10 06 03 55 04 03 13 09 44
        48 20 54 65 73 74 43 41

   TrailingInfo: DER-encoded Issuer/recipient DN (from the certificate
   described in step 1)

        30 48 31 0B 30 09 06 03 55 04 06 13 02 55 53 31
        11 30 0F 06 03 55 04 0A 13 08 58 45 54 49 20 49
        6E 63 31 10 30 0E 06 03 55 04 0B 13 07 54 65 73
        74 69 6E 67 31 14 30 12 06 03 55 04 03 13 0B 52
        6F 6F 74 20 44 53 41 20 43 41

      K:
        B1 91 D7 DB 4F C5 EF EF AC 9A C5 44 5A 6D 42 28
        DC 70 7B DA

















Schaad & Prafullchandra      Standards Track                   [Page 34]
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RFC 6955                    DH POP Algorithms                   May 2013


   TBS: the "text" for computing the SHA-1 HMAC.

      30 82 02 98 02 01 00 30 4E 31 0B 30 09 06 03 55
      04 06 13 02 55 53 31 11 30 0F 06 03 55 04 0A 13
      08 58 45 54 49 20 49 6E 63 31 10 30 0E 06 03 55
      04 0B 13 07 54 65 73 74 69 6E 67 31 1A 30 18 06
      03 55 04 03 13 11 50 4B 49 58 20 45 78 61 6D 70
      6C 65 20 55 73 65 72 30 82 02 41 30 82 01 B6 06
      07 2A 86 48 CE 3E 02 01 30 82 01 A9 02 81 81 00
      94 84 E0 45 6C 7F 69 51 62 3E 56 80 7C 68 E7 C5
      A9 9E 9E 74 74 94 ED 90 8C 1D C4 E1 4A 14 82 F5
      D2 94 0C 19 E3 B9 10 BB 11 B9 E5 A5 FB 8E 21 51
      63 02 86 AA 06 B8 21 36 B6 7F 36 DF D1 D6 68 5B
      79 7C 1D 5A 14 75 1F 6A 93 75 93 CE BB 97 72 8A
      F0 0F 23 9D 47 F6 D4 B3 C7 F0 F4 E6 F6 2B C2 32
      E1 89 67 BE 7E 06 AE F8 D0 01 6B 8B 2A F5 02 D7
      B6 A8 63 94 83 B0 1B 31 7D 52 1A DE E5 03 85 27
      02 81 80 26 A6 32 2C 5A 2B D4 33 2B 5C DC 06 87
      53 3F 90 06 61 50 38 3E D2 B9 7D 81 1C 12 10 C5
      0C 53 D4 64 D1 8E 30 07 08 8C DD 3F 0A 2F 2C D6
      1B 7F 57 86 D0 DA BB 6E 36 2A 18 E8 D3 BC 70 31
      7A 48 B6 4E 18 6E DD 1F 22 06 EB 3F EA D4 41 69
      D9 9B DE 47 95 7A 72 91 D2 09 7F 49 5C 3B 03 33
      51 C8 F1 39 9A FF 04 D5 6E 7E 94 3D 03 B8 F6 31
      15 26 48 95 A8 5C DE 47 88 B4 69 3A 00 A7 86 9E
      DA D1 CD 02 21 00 E8 72 FA 96 F0 11 40 F5 F2 DC
      FD 3B 5D 78 94 B1 85 01 E5 69 37 21 F7 25 B9 BA
      71 4A FC 60 30 FB 02 61 00 A3 91 01 C0 A8 6E A4
      4D A0 56 FC 6C FE 1F A7 B0 CD 0F 94 87 0C 25 BE
      97 76 8D EB E5 A4 09 5D AB 83 CD 80 0B 35 67 7F
      0C 8E A7 31 98 32 85 39 40 9D 11 98 D8 DE B8 7F
      86 9B AF 8D 67 3D B6 76 B4 61 2F 21 E1 4B 0E 68
      FF 53 3E 87 DD D8 71 56 68 47 DC F7 20 63 4B 3C
      5F 78 71 83 E6 70 9E E2 92 30 1A 03 15 00 1C D5
      3A 0D 17 82 6D 0A 81 75 81 46 10 8E 3E DB 09 E4
      98 34 02 01 37 03 81 84 00 02 81 80 13 63 A1 85
      04 8C 46 A8 88 EB F4 5E A8 93 74 AE FD AE 9E 96
      27 12 65 C4 4C 07 06 3E 18 FE 94 B8 A8 79 48 BD
      2E 34 B6 47 CA 04 30 A1 EC 33 FD 1A 0B 2D 9E 50
      C9 78 0F AE 6A EC B5 6B 6A BE B2 5C DA B2 9F 78
      2C B9 77 E2 79 2B 25 BF 2E 0B 59 4A 93 4B F8 B3
      EC 81 34 AE 97 47 52 E0 A8 29 98 EC D1 B0 CA 2B
      6F 7A 8B DB 4E 8D A5 15 7E 7E AF 33 62 09 9E 0F
      11 44 8C C1 8D A2 11 9E 53 EF B2 E8







Schaad & Prafullchandra      Standards Track                   [Page 35]
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RFC 6955                    DH POP Algorithms                   May 2013


   Certification Request:

   0 30 793: SEQUENCE {
   4 30 664:   SEQUENCE {
   8 02   1:     INTEGER 0
  11 30  78:     SEQUENCE {
  13 31  11:       SET {
  15 30   9:         SEQUENCE {
  17 06   3:           OBJECT IDENTIFIER countryName (2 5 4 6)
  22 13   2:           PrintableString 'US'
           :           }
           :         }
  26 31  17:       SET {
  28 30  15:         SEQUENCE {
  30 06   3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
  35 13   8:           PrintableString 'XETI Inc'
           :           }
           :         }
  45 31  16:       SET {
  47 30  14:         SEQUENCE {
  49 06   3:           OBJECT IDENTIFIER organizationalUnitName (2 5 4
                                 11)
  54 13   7:           PrintableString 'Testing'
           :           }
           :         }
  63 31  26:       SET {
  65 30  24:         SEQUENCE {
  67 06   3:           OBJECT IDENTIFIER commonName (2 5 4 3)
  72 13  17:           PrintableString 'PKIX Example User'
           :           }
           :         }
           :       }
  91 30 577:     SEQUENCE {
  95 30 438:       SEQUENCE {
  99 06   7:         OBJECT IDENTIFIER dhPublicKey (1 2 840 10046 2 1)
 108 30 425:         SEQUENCE {
 112 02 129:           INTEGER
           :             00 94 84 E0 45 6C 7F 69 51 62 3E 56 80 7C 68 E7
           :             C5 A9 9E 9E 74 74 94 ED 90 8C 1D C4 E1 4A 14 82
           :             F5 D2 94 0C 19 E3 B9 10 BB 11 B9 E5 A5 FB 8E 21
           :             51 63 02 86 AA 06 B8 21 36 B6 7F 36 DF D1 D6 68
           :             5B 79 7C 1D 5A 14 75 1F 6A 93 75 93 CE BB 97 72
           :             8A F0 0F 23 9D 47 F6 D4 B3 C7 F0 F4 E6 F6 2B C2
           :             32 E1 89 67 BE 7E 06 AE F8 D0 01 6B 8B 2A F5 02
           :             D7 B6 A8 63 94 83 B0 1B 31 7D 52 1A DE E5 03 85
           :             27





Schaad & Prafullchandra      Standards Track                   [Page 36]
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RFC 6955                    DH POP Algorithms                   May 2013


 244 02 128:           INTEGER
           :             26 A6 32 2C 5A 2B D4 33 2B 5C DC 06 87 53 3F 90
           :             06 61 50 38 3E D2 B9 7D 81 1C 12 10 C5 0C 53 D4
           :             64 D1 8E 30 07 08 8C DD 3F 0A 2F 2C D6 1B 7F 57
           :             86 D0 DA BB 6E 36 2A 18 E8 D3 BC 70 31 7A 48 B6
           :             4E 18 6E DD 1F 22 06 EB 3F EA D4 41 69 D9 9B DE
           :             47 95 7A 72 91 D2 09 7F 49 5C 3B 03 33 51 C8 F1
           :             39 9A FF 04 D5 6E 7E 94 3D 03 B8 F6 31 15 26 48
           :             95 A8 5C DE 47 88 B4 69 3A 00 A7 86 9E DA D1 CD
 375 02  33:           INTEGER
           :             00 E8 72 FA 96 F0 11 40 F5 F2 DC FD 3B 5D 78 94
           :             B1 85 01 E5 69 37 21 F7 25 B9 BA 71 4A FC 60 30
           :             FB
 410 02  97:           INTEGER
           :             00 A3 91 01 C0 A8 6E A4 4D A0 56 FC 6C FE 1F A7
           :             B0 CD 0F 94 87 0C 25 BE 97 76 8D EB E5 A4 09 5D
           :             AB 83 CD 80 0B 35 67 7F 0C 8E A7 31 98 32 85 39
           :             40 9D 11 98 D8 DE B8 7F 86 9B AF 8D 67 3D B6 76
           :             B4 61 2F 21 E1 4B 0E 68 FF 53 3E 87 DD D8 71 56
           :             68 47 DC F7 20 63 4B 3C 5F 78 71 83 E6 70 9E E2
           :             92
 509 30  26:           SEQUENCE {
 511 03  21:             BIT STRING 0 unused bits
           :               1C D5 3A 0D 17 82 6D 0A 81 75 81 46 10 8E 3E
           :               DB 09 E4 98 34
 534 02   1:             INTEGER 55
           :             }
           :           }
           :         }
 537 03 132:       BIT STRING 0 unused bits
           :         02 81 80 13 63 A1 85 04 8C 46 A8 88 EB F4 5E A8
           :         93 74 AE FD AE 9E 96 27 12 65 C4 4C 07 06 3E 18
           :         FE 94 B8 A8 79 48 BD 2E 34 B6 47 CA 04 30 A1 EC
           :         33 FD 1A 0B 2D 9E 50 C9 78 0F AE 6A EC B5 6B 6A
           :         BE B2 5C DA B2 9F 78 2C B9 77 E2 79 2B 25 BF 2E
           :         0B 59 4A 93 4B F8 B3 EC 81 34 AE 97 47 52 E0 A8
           :         29 98 EC D1 B0 CA 2B 6F 7A 8B DB 4E 8D A5 15 7E
           :         7E AF 33 62 09 9E 0F 11 44 8C C1 8D A2 11 9E 53
           :         EF B2 E8
           :       }
           :     }
 672 30  12:   SEQUENCE {
 674 06   8:     OBJECT IDENTIFIER dh-sig-hmac-sha1 (1 3 6 1 5 5 7 6 3)
 684 05   0:     NULL
           :     }






Schaad & Prafullchandra      Standards Track                   [Page 37]
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RFC 6955                    DH POP Algorithms                   May 2013


 686 03 109:   BIT STRING 0 unused bits
           :     30 6A 30 52 30 48 31 0B 30 09 06 03 55 04 06 13
           :     02 55 53 31 11 30 0F 06 03 55 04 0A 13 08 58 45
           :     54 49 20 49 6E 63 31 10 30 0E 06 03 55 04 0B 13
           :     07 54 65 73 74 69 6E 67 31 14 30 12 06 03 55 04
           :     03 13 0B 52 6F 6F 74 20 44 53 41 20 43 41 02 06
           :     00 DA 39 B6 E2 CB 04 14 2D 05 77 FE 5E 8F 65 F5
           :     AF AD C9 5C 9B 02 C0 A8 88 29 61 63
           :   }

   Signature verification requires CA's private key, the CA certificate,
   and the generated Certification Request.

   CA DH private key:

       x:  3E 5D AD FD E5 F4 6B 1B 61 5E 18 F9 0B 84 74 a7
           52 1E D6 92 BC 34 94 56 F3 0C BE DA 67 7A DD 7D

Appendix C.  Example of Discrete Log Signature

   Step 1.  Generate a DH key with length of q being 256 bits.

      p:
        94 84 E0 45 6C 7F 69 51 62 3E 56 80 7C 68 E7 C5
        A9 9E 9E 74 74 94 ED 90 8C 1D C4 E1 4A 14 82 F5
        D2 94 0C 19 E3 B9 10 BB 11 B9 E5 A5 FB 8E 21 51
        63 02 86 AA 06 B8 21 36 B6 7F 36 DF D1 D6 68 5B
        79 7C 1D 5A 14 75 1F 6A 93 75 93 CE BB 97 72 8A
        F0 0F 23 9D 47 F6 D4 B3 C7 F0 F4 E6 F6 2B C2 32
        E1 89 67 BE 7E 06 AE F8 D0 01 6B 8B 2A F5 02 D7
        B6 A8 63 94 83 B0 1B 31 7D 52 1A DE E5 03 85 27

      q:
        E8 72 FA 96 F0 11 40 F5 F2 DC FD 3B 5D 78 94 B1
        85 01 E5 69 37 21 F7 25 B9 BA 71 4A FC 60 30 FB

      g:
        26 A6 32 2C 5A 2B D4 33 2B 5C DC 06 87 53 3F 90
        06 61 50 38 3E D2 B9 7D 81 1C 12 10 C5 0C 53 D4
        64 D1 8E 30 07 08 8C DD 3F 0A 2F 2C D6 1B 7F 57
        86 D0 DA BB 6E 36 2A 18 E8 D3 BC 70 31 7A 48 B6
        4E 18 6E DD 1F 22 06 EB 3F EA D4 41 69 D9 9B DE
        47 95 7A 72 91 D2 09 7F 49 5C 3B 03 33 51 C8 F1
        39 9A FF 04 D5 6E 7E 94 3D 03 B8 F6 31 15 26 48
        95 A8 5C DE 47 88 B4 69 3A 00 A7 86 9E DA D1 CD






Schaad & Prafullchandra      Standards Track                   [Page 38]
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RFC 6955                    DH POP Algorithms                   May 2013


      j:
        A3 91 01 C0 A8 6E A4 4D A0 56 FC 6C FE 1F A7 B0
        CD 0F 94 87 0C 25 BE 97 76 8D EB E5 A4 09 5D AB
        83 CD 80 0B 35 67 7F 0C 8E A7 31 98 32 85 39 40
        9D 11 98 D8 DE B8 7F 86 9B AF 8D 67 3D B6 76 B4
        61 2F 21 E1 4B 0E 68 FF 53 3E 87 DD D8 71 56 68
        47 DC F7 20 63 4B 3C 5F 78 71 83 E6 70 9E E2 92

      y:
        5F CF 39 AD 62 CF 49 8E D1 CE 66 E2 B1 E6 A7 01
        4D 05 C2 77 C8 92 52 42 A9 05 A4 DB E0 46 79 50
        A3 FC 99 3D 3D A6 9B A9 AD BC 62 1C 69 B7 11 A1
        C0 2A F1 85 28 F7 68 FE D6 8F 31 56 22 4D 0A 11
        6E 72 3A 02 AF 0E 27 AA F9 ED CE 05 EF D8 59 92
        C0 18 D7 69 6E BD 70 B6 21 D1 77 39 21 E1 AF 7A
        3A CF 20 0A B4 2C 69 5F CF 79 67 20 31 4D F2 C6
        ED 23 BF C4 BB 1E D1 71 40 2C 07 D6 F0 8F C5 1A

      seed:
        1C D5 3A 0D 17 82 6D 0A 81 75 81 46 10 8E 3E DB
        09 E4 98 34

      C:
        00000037

      x:
        3E 5D AD FD E5 F4 6B 1B 61 5E 18 F9 0B 84 74 a7
        52 1E D6 92 BC 34 94 56 F3 0C BE DA 67 7A DD 7D

   Step 2.  Form the value to be signed and hash with SHA1.  The result
   of the hash for this example is:

        5f a2 69 b6 4b 22 91 22 6f 4c fe 68 ec 2b d1 c6
        d4 21 e5 2c

   Step 3.  The hash value needs to be expanded, since |q| = 256.  This
   is done by hashing the hash with SHA1 and appending it to the
   original hash.  The value after this step is:

        5f a2 69 b6 4b 22 91 22 6f 4c fe 68 ec 2b d1 c6
        d4 21 e5 2c 64 92 8b c9 5e 34 59 70 bd 62 40 ad
        6f 26 3b f7 1c a3 b2 cb









Schaad & Prafullchandra      Standards Track                   [Page 39]
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RFC 6955                    DH POP Algorithms                   May 2013


   Next, the first 255 bits of this value are taken to be the resulting
   "hash" value.  Note that in this case a shift of one bit right is
   done, since the result is to be treated as an integer:

        2f d1 34 db 25 91 48 91 37 a6 7f 34 76 15 e8 e3
        6a 10 f2 96 32 49 45 e4 af 1a 2c b8 5e b1 20 56

   Step 4.  The signature value is computed.  In this case, you get the
   values:

      r:
        A1 B5 B4 90 01 34 6B A0 31 6A 73 F5 7D F6 5C 14
        43 52 D2 10 BF 86 58 87 F7 BC 6E 5A 77 FF C3 4B

      s:
        59 40 45 BC 6F 0D DC FF 9D 55 40 1E C4 9E 51 3D
        66 EF B2 FF 06 40 9A 39 68 75 81 F7 EC 9E BE A1

   The encoded signature value is then:

      30 45 02 21 00 A1 B5 B4 90 01 34 6B A0 31 6A 73
      F5 7D F6 5C 14 43 52 D2 10 BF 86 58 87 F7 BC 6E
      5A 77 FF C3 4B 02 20 59 40 45 BC 6F 0D DC FF 9D
      55 40 1E C4 9E 51 3D 66 EF B2 FF 06 40 9A 39 68
      75 81 F7 EC 9E BE A1

      Result:
        30 82 02 c2 30 82 02 67 02 01 00 30 1b 31 19 30
        17 06 03 55 04 03 13 10 49 45 54 46 20 50 4b 49
        58 20 53 41 4d 50 4c 45 30 82 02 41 30 82 01 b6
        06 07 2a 86 48 ce 3e 02 01 30 82 01 a9 02 81 81
        00 94 84 e0 45 6c 7f 69 51 62 3e 56 80 7c 68 e7
        c5 a9 9e 9e 74 74 94 ed 90 8c 1d c4 e1 4a 14 82
        f5 d2 94 0c 19 e3 b9 10 bb 11 b9 e5 a5 fb 8e 21
        51 63 02 86 aa 06 b8 21 36 b6 7f 36 df d1 d6 68
        5b 79 7c 1d 5a 14 75 1f 6a 93 75 93 ce bb 97 72
        8a f0 0f 23 9d 47 f6 d4 b3 c7 f0 f4 e6 f6 2b c2
        32 e1 89 67 be 7e 06 ae f8 d0 01 6b 8b 2a f5 02
        d7 b6 a8 63 94 83 b0 1b 31 7d 52 1a de e5 03 85
        27 02 81 80 26 a6 32 2c 5a 2b d4 33 2b 5c dc 06
        87 53 3f 90 06 61 50 38 3e d2 b9 7d 81 1c 12 10
        c5 0c 53 d4 64 d1 8e 30 07 08 8c dd 3f 0a 2f 2c
        d6 1b 7f 57 86 d0 da bb 6e 36 2a 18 e8 d3 bc 70
        31 7a 48 b6 4e 18 6e dd 1f 22 06 eb 3f ea d4 41
        69 d9 9b de 47 95 7a 72 91 d2 09 7f 49 5c 3b 03
        33 51 c8 f1 39 9a ff 04 d5 6e 7e 94 3d 03 b8 f6
        31 15 26 48 95 a8 5c de 47 88 b4 69 3a 00 a7 86
        9e da d1 cd 02 21 00 e8 72 fa 96 f0 11 40 f5 f2



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RFC 6955                    DH POP Algorithms                   May 2013


        dc fd 3b 5d 78 94 b1 85 01 e5 69 37 21 f7 25 b9
        ba 71 4a fc 60 30 fb 02 61 00 a3 91 01 c0 a8 6e
        a4 4d a0 56 fc 6c fe 1f a7 b0 cd 0f 94 87 0c 25
        be 97 76 8d eb e5 a4 09 5d ab 83 cd 80 0b 35 67
        7f 0c 8e a7 31 98 32 85 39 40 9d 11 98 d8 de b8
        7f 86 9b af 8d 67 3d b6 76 b4 61 2f 21 e1 4b 0e
        68 ff 53 3e 87 dd d8 71 56 68 47 dc f7 20 63 4b
        3c 5f 78 71 83 e6 70 9e e2 92 30 1a 03 15 00 1c
        d5 3a 0d 17 82 6d 0a 81 75 81 46 10 8e 3e db 09
        e4 98 34 02 01 37 03 81 84 00 02 81 80 5f cf 39
        ad 62 cf 49 8e d1 ce 66 e2 b1 e6 a7 01 4d 05 c2
        77 c8 92 52 42 a9 05 a4 db e0 46 79 50 a3 fc 99
        3d 3d a6 9b a9 ad bc 62 1c 69 b7 11 a1 c0 2a f1
        85 28 f7 68 fe d6 8f 31 56 22 4d 0a 11 6e 72 3a
        02 af 0e 27 aa f9 ed ce 05 ef d8 59 92 c0 18 d7
        69 6e bd 70 b6 21 d1 77 39 21 e1 af 7a 3a cf 20
        0a b4 2c 69 5f cf 79 67 20 31 4d f2 c6 ed 23 bf
        c4 bb 1e d1 71 40 2c 07 d6 f0 8f c5 1a a0 00 30
        0c 06 08 2b 06 01 05 05 07 06 04 05 00 03 47 00
        30 44 02 20 54 d9 43 8d 0f 9d 42 03 d6 09 aa a1
        9a 3c 17 09 ae bd ee b3 d1 a0 00 db 7d 8c b8 e4
        56 e6 57 7b 02 20 44 89 b1 04 f5 40 2b 5f e7 9c
        f9 a4 97 50 0d ad c3 7a a4 2b b2 2d 5d 79 fb 38
        8a b4 df bb 88 bc

   Decoded version of result:

   0 30  707: SEQUENCE {
   4 30  615:   SEQUENCE {
   8 02    1:     INTEGER 0
  11 30   27:     SEQUENCE {
  13 31   25:       SET {
  15 30   23:         SEQUENCE {
  17 06    3:           OBJECT IDENTIFIER commonName (2 5 4 3)
  22 13   16:           PrintableString 'IETF PKIX SAMPLE'
            :           }
            :         }
            :       }
  40 30  577:     SEQUENCE {
  44 30  438:       SEQUENCE {
  48 06    7:         OBJECT IDENTIFIER dhPublicNumber (1 2 840 10046 2
                                  1)









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RFC 6955                    DH POP Algorithms                   May 2013


  57 30  425:         SEQUENCE {
  61 02  129:           INTEGER
            :            00 94 84 E0 45 6C 7F 69 51 62 3E 56 80 7C 68 E7
            :            C5 A9 9E 9E 74 74 94 ED 90 8C 1D C4 E1 4A 14 82
            :            F5 D2 94 0C 19 E3 B9 10 BB 11 B9 E5 A5 FB 8E 21
            :            51 63 02 86 AA 06 B8 21 36 B6 7F 36 DF D1 D6 68
            :            5B 79 7C 1D 5A 14 75 1F 6A 93 75 93 CE BB 97 72
            :            8A F0 0F 23 9D 47 F6 D4 B3 C7 F0 F4 E6 F6 2B C2
            :            32 E1 89 67 BE 7E 06 AE F8 D0 01 6B 8B 2A F5 02
            :            D7 B6 A8 63 94 83 B0 1B 31 7D 52 1A DE E5 03 85
            :            27
 193 02  128:           INTEGER
            :            26 A6 32 2C 5A 2B D4 33 2B 5C DC 06 87 53 3F 90
            :            06 61 50 38 3E D2 B9 7D 81 1C 12 10 C5 0C 53 D4
            :            64 D1 8E 30 07 08 8C DD 3F 0A 2F 2C D6 1B 7F 57
            :            86 D0 DA BB 6E 36 2A 18 E8 D3 BC 70 31 7A 48 B6
            :            4E 18 6E DD 1F 22 06 EB 3F EA D4 41 69 D9 9B DE
            :            47 95 7A 72 91 D2 09 7F 49 5C 3B 03 33 51 C8 F1
            :            39 9A FF 04 D5 6E 7E 94 3D 03 B8 F6 31 15 26 48
            :            95 A8 5C DE 47 88 B4 69 3A 00 A7 86 9E DA D1 CD
 324 02   33:           INTEGER
            :            00 E8 72 FA 96 F0 11 40 F5 F2 DC FD 3B 5D 78 94
            :            B1 85 01 E5 69 37 21 F7 25 B9 BA 71 4A FC 60 30
            :            FB
 359 02   97:           INTEGER
            :            00 A3 91 01 C0 A8 6E A4 4D A0 56 FC 6C FE 1F A7
            :            B0 CD 0F 94 87 0C 25 BE 97 76 8D EB E5 A4 09 5D
            :            AB 83 CD 80 0B 35 67 7F 0C 8E A7 31 98 32 85 39
            :            40 9D 11 98 D8 DE B8 7F 86 9B AF 8D 67 3D B6 76
            :            B4 61 2F 21 E1 4B 0E 68 FF 53 3E 87 DD D8 71 56
            :            68 47 DC F7 20 63 4B 3C 5F 78 71 83 E6 70 9E E2
            :            92
 458 30   26:           SEQUENCE {
 460 03   21:             BIT STRING 0 unused bits
            :            1C D5 3A 0D 17 82 6D 0A 81 75 81 46 10 8E 3E DB
            :            09 E4 98 34
 483 02    1:             INTEGER 55
            :             }
            :           }
            :         }











Schaad & Prafullchandra      Standards Track                   [Page 42]
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RFC 6955                    DH POP Algorithms                   May 2013


 486 03  132:       BIT STRING 0 unused bits
            :         02 81 80 5F CF 39 AD 62 CF 49 8E D1 CE 66 E2 B1
            :         E6 A7 01 4D 05 C2 77 C8 92 52 42 A9 05 A4 DB E0
            :         46 79 50 A3 FC 99 3D 3D A6 9B A9 AD BC 62 1C 69
            :         B7 11 A1 C0 2A F1 85 28 F7 68 FE D6 8F 31 56 22
            :         4D 0A 11 6E 72 3A 02 AF 0E 27 AA F9 ED CE 05 EF
            :         D8 59 92 C0 18 D7 69 6E BD 70 B6 21 D1 77 39 21
            :         E1 AF 7A 3A CF 20 0A B4 2C 69 5F CF 79 67 20 31
            :         4D F2 C6 ED 23 BF C4 BB 1E D1 71 40 2C 07 D6 F0
            :         8F C5 1A
            :       }
 621 A0    0:     [0]
            :     }
 623 30   12:   SEQUENCE {
 625 06    8:     OBJECT IDENTIFIER '1 3 6 1 5 5 7 6 4'
 635 05    0:     NULL
            :     }
 637 03   72:   BIT STRING 0 unused bits
            :     30 45 02 21 00 A1 B5 B4 90 01 34 6B A0 31 6A 73
            :     F5 7D F6 5C 14 43 52 D2 10 BF 86 58 87 F7 BC 6E
            :     5A 77 FF C3 4B 02 20 59 40 45 BC 6F 0D DC FF 9D
            :     55 40 1E C4 9E 51 3D 66 EF B2 FF 06 40 9A 39 68
            :     75 81 F7 EC 9E BE A1
            :   }

Authors' Addresses

   Jim Schaad
   Soaring Hawk Consulting

   EMail: ietf@augustcellars.com


   Hemma Prafullchandra
   HyTrust, Inc.
   1975 W. El Camino Real, Suite 203
   Mountain View, CA  94040
   USA

   Phone: (650) 681-8100
   EMail: HPrafullchandra@hytrust.com










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