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Request for Comments: 7091
Updates: 5832
Category: Informational
ISSN: 2070-1721
V. Dolmatov, Ed.
A. Degtyarev
Cryptocom, Ltd.
December 2013

GOST R 34.10-2012: Digital Signature Algorithm

Abstract

This document provides information about the Russian Federal standard for digital signatures (GOST R 34.10-2012), which is one of the Russian cryptographic standard algorithms (called GOST algorithms). Recently, Russian cryptography is being used in Internet applications, and this document provides information for developers and users of GOST R 34.10-2012 regarding digital signature generation and verification. This document updates RFC 5832.

Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes.

This is a contribution to the RFC Series, independently of any other RFC stream. The RFC Editor has chosen to publish this document at its discretion and makes no statement about its value for implementation or deployment. Documents approved for publication by the RFC Editor are not a candidate for any level of Internet Standard; see 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/rfc7091.

Copyright Notice

Copyright © 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 carefully, as they describe your rights and restrictions with respect to this document.

Table of Contents

   1. Introduction ....................................................2
      1.1. General Information ........................................2
      1.2. The Purpose of GOST R 34.10-2012 ...........................3
      1.3. Requirements Language ......................................3
   2. Scope ...........................................................3
   3. Definitions and Notations .......................................4
      3.1. Definitions ................................................4
      3.2. Notations ..................................................6
   4. General Statements ..............................................7
   5. Mathematical Conventions ........................................8
      5.1. Mathematical Definitions ...................................9
      5.2. Digital Signature Parameters ..............................10
      5.3. Binary Vectors ............................................12
   6. Main Processes .................................................12
      6.1. Digital Signature Generation Process ......................13
      6.2. Digital Signature Verification ............................13
   7. Test Examples (Appendix to GOST R 34.10-2012) ..................14
      7.1. The Digital Signature Scheme Parameters ...................15
      7.2. Digital Signature Process (Algorithm I) ...................17
      7.3. Verification Process of Digital Signature (Algorithm II) ..18
   8. Security Considerations ........................................19
   9. References .....................................................19
      9.1. Normative References ......................................19
      9.2. Informative References ....................................20

1. Introduction

1.1. General Information

   1.  GOST R 34.10-2012 [GOST3410-2012] was developed by the Center for
       Information Protection and Special Communications of the Federal
       Security Service of the Russian Federation with participation of
       the open joint-stock company "Information Technologies and
       Communication Systems" (InfoTeCS JSC).
  1. GOST R 34.10-2012 was approved and introduced by Decree #215 of the Federal Agency on Technical Regulating and Metrology on 07.08.2012.
   3.  GOST R 34.10-2012 replaces GOST R 34.10-2001 [GOST3410-2001], a
       national standard of the Russian Federation.

GOST R 34.10-2001 is superseded by GOST R 34.10-2012 from 1 January 2013. That means that all new systems that are presented for certification MUST use GOST R 34.10-2012 and MAY use

GOST R 34.10-2001 also for maintaining compatibility with existing systems. Usage of GOST R 34.10-2001 in current systems is allowed at least for a 5-year period.

This document updates RFC 5832 [RFC5832].

This document is an English translation of GOST R 34.10-2012; [RFC6986] is an English translation of GOST R 34.11-2012; and [RFC5832] is an English translation of GOST R 34.10-2001.

Terms and conceptions of this standard comply with the following international standards: 

   o  ISO 2382-2 [ISO2382-2],
   o  ISO/IEC 9796 [ISO9796-2][ISO9796-3],
   o  series of standards ISO/IEC 14888 [ISO14888-1] [ISO14888-2]
      [ISO14888-3] [ISO14888-4], and
   o  series of standards ISO/IEC 10118 [ISO10118-1] [ISO10118-2]
      [ISO10118-3] [ISO10118-4].

1.2. The Purpose of GOST R 34.10-2012

GOST R 34.10-2012 describes the generation and verification processes for digital signatures, based on operations with an elliptic curve points group, defined over a prime finite field.

The necessity for developing this standard is caused by the need to implement digital signatures of varying resistance due to growth of computer technology. Digital signature security is based on the complexity of discrete logarithm calculation in an elliptic curve points group and also on the security of the hash function used (according to GOST R 34.11-2012 [GOST3411-2012]).

1.3. Requirements Language

   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 RFC 2119 [RFC2119].

2. Scope

GOST R 34.10-2012 defines an electronic digital signature (or simply digital signature) scheme, digital signature generation and verification processes for a given message (document), meant for transmission via insecure public telecommunication channels in data processing systems of different purposes.

Use of a digital signature based on GOST R 34.10-2012 makes transmitted messages more resistant to forgery and loss of integrity, in comparison with the digital signature scheme prescribed by the previous standard.

GOST R 34.10-2012 is recommended for the creation, operation, and modernization of data processing systems of various purposes.

3. Definitions and Notations

3.1. Definitions

The following terms are used in the standard:

appendix: bit string that is formed by a digital signature and by the

arbitrary text field [ISO14888-1].

signature key: element of secret data that is specific to the subject

and used only by this subject during the signature generation process [ISO14888-1].

verification key: element of data mathematically linked to the

signature key data element that is used by the verifier during the digital signature verification process [ISO14888-1].

domain parameter: element of data that is common for all the subjects

of the digital signature scheme, known or accessible to all the subjects [ISO14888-1].

signed message: a set of data elements that consists of the message

and the appendix, which is a part of the message [ISO14888-1].

pseudorandom number sequence: a sequence of numbers that is obtained

during some arithmetic (calculation) process, used in a specific case instead of a true random number sequence.

random number sequence: a sequence of numbers of which none can be

predicted (calculated) using only the preceding numbers of the same sequence.

verification process: a process that uses the signed message, the

verification key, and the digital signature scheme parameters as initial data and that gives the conclusion about digital signature validity or invalidity as a result [ISO14888-1].

signature generation process: a process that uses the message, the

signature key, and the digital signature scheme parameters as initial data and that generates the digital signature as the result [ISO14888-1].

witness: element of data that states to the verifier whether the

digital signature is valid or invalid.

random number: a number chosen from the definite number set in such a

way that every number from the set can be chosen with equal probability.

message:

string of bits of a limited length [ISO14888-1].

hash code: string of bits that is a result of the hash function

[ISO14888-1].

hash function: the function that maps bit strings onto bit strings of

fixed length observing the following properties:

  1. it is difficult to calculate the input data that is the pre- image of the given function value;
  1. it is difficult to find another input data that is the pre- image of the same function value as is the given input data; and
  1. it is difficult to find a pair of different input data that produces the same hash function value.
      [ISO14888-1]

Notes:

  1. Property 1 in the context of the digital signature area means that it is impossible to recover the initial message using the digital signature; property 2 means that it is difficult to find another (falsified) message that produces the same digital signature as a given message; property 3 means that it is difficult to find a pair of different messages that both produce the same signature.
  1. In this standard, the terms "hash function", "cryptographic hash function", "hashing function", and "cryptographic hashing function" are synonymous to provide terminological succession to native legal documents currently in force and scientific publications.

(electronic) digital signature: string of bits that are obtained as a

result of the signature generation process [ISO14888-1].

Notes:

  1. A string of bits that is a signature may have an internal structure depending on the specific signature generation mechanism.
  1. In this standard, the terms "electronic signature", "digital signature", and "electronic digital signature" are synonymous to provide terminological succession to native legal documents currently in force and scientific publications.

3.2. Notations

The following notations are used in this standard: 

   V_l          set of all binary vectors of an l-bit length
   
   V_all        set of all binary vectors of an arbitrary finite length
   
   Z            set of all integers
   
   p            prime number, p > 3
   
   GF(p)        finite prime field represented by a set of integers {0,
                1, ..., p - 1}
   
   b (mod p)    minimal non-negative number, congruent to b modulo p
   
   M            user's message, M belongs to V_all

(H1 || H2 ) concatenation of two binary vectors 

   a, b         elliptic curve coefficients
   
   m            points of the elliptic curve group order
   
   q            subgroup order of group of points of the elliptic curve
   
   O            zero point of the elliptic curve
   
   P            elliptic curve point of order q
   
   d            integer - a signature key
   
   Q            elliptic curve point - a verification key
   zeta         digital signature for the message M
   
   ^            the power operator
   
   /=           non-equality
   
   sqrt         square root

4. General Statements

A commonly accepted digital signature scheme (model) consists of three processes:

  • generation of a pair of keys (for signature generation and for signature verification),
  • signature generation, and
  • signature verification.

In GOST R 34.10-2012, a process for generating a pair of keys (for signature and verification) is not defined. Characteristics and ways to realize the process are defined by involved subjects, who determine corresponding parameters by their agreement.

The digital signature mechanism is defined by the realization of two main processes (Section 6): 

   -  signature generation (Section 6.1), and
  • signature verification (Section 6.2).

The digital signature is meant for the authentication of the signatory of the electronic message. Besides, digital signature usage gives an opportunity to provide the following properties during signed message transmission:

  • realization of control of the transmitted signed message integrity,
  • proof of the authorship of the signatory of the message, and
  • protection of the message against possible forgery.

A schematic representation of the signed message is shown in Figure 1. 

                                   appendix
                                      |
                      +-------------------------------+
                      |                               |
      +-----------+   +------------------------+- - - +
      | message M |---| digital signature zeta | text |
      +-----------+   +------------------------+- - - +

Figure 1: Signed Message Scheme

The field "digital signature" is supplemented by the field "text" that can contain, for example, identifiers of the signatory of the message and/or time label.

The digital signature scheme defined in GOST R 34.10-2012 must be implemented using operations of the elliptic curve points group, defined over a finite prime field, and also with the use of the hash function.

The cryptographic security of the digital signature scheme is based on the complexity of solving the problem of the calculation of the discrete logarithm in the elliptic curve points group and also on the security of the hash function used. The hash function calculation algorithm is defined in GOST R 34.11-2012 [GOST3411-2012].

The digital signature scheme parameters needed for signature generation and verification are defined in Section 5.2. This standard provides the opportunity to select one of two options for parameter requirements.

GOST R 34.10-2012 does not determine the process for generating the parameters needed for the digital signature scheme. Possible sets of these parameters are defined, for example, in [RFC4357].

The digital signature represented as a binary vector of a 512- or 1024-bit length must be calculated using a definite set of rules, as stated in Section 6.1.

The digital signature of the received message is accepted or denied in accordance with the set of rules, as stated in Section 6.2.

5. Mathematical Conventions

To define a digital signature scheme, it is necessary to describe basic mathematical objects used in the signature generation and verification processes. This section lays out basic mathematical definitions and requirements for the parameters of the digital signature scheme.

5.1. Mathematical Definitions

Suppose a prime number p > 3 is given. Then, an elliptic curve E, defined over a finite prime field GF(p), is the set of number pairs (x,y), where x and y belong to Fp, satisfying the identity: 

   y^2 = x^3 + a * x + b (mod p),                                    (1)

where a, b belong to GF(p) and 4 * a^3 + 27 * b^2 is not congruent to zero modulo p.

An invariant of the elliptic curve is the value J(E), satisfying the equality: 

                      4 * a^3
   J(E) = 1728 * ------------------ (mod p)                          (2)
                 4 * a^3 + 27 * b^2

Elliptic curve E coefficients a, b are defined in the following way using the invariant J(E): 

   | a = 3 * k (mod p),
   |                                                                 (3)
   | b = 2 * k (mod p),
   
                 J(E)
   where k = ----------- (mod p), J(E) /= 0 or 1728
             1728 - J(E)

The pairs (x, y) satisfying the identity (1) are called "the elliptic curve E points"; x and y are called x- and y-coordinates of the point, correspondingly.

We will denote elliptic curve points as Q(x, y) or just Q. Two elliptic curve points are equal if their x- and y-coordinates are equal.

On the set of all elliptic curve E points, we will define the addition operation, denoted by "+". For two arbitrary elliptic curve E points Q1 (x1, y1) and Q2 (x2, y2), we will consider several variants.

Suppose coordinates of points Q1 and Q2 satisfy the condition x1 /= x2. In this case, their sum is defined as a point Q3 (x3, y3), with coordinates defined by congruencies: 

   | x3 = lambda^2 - x1 - x2 (mod p),
   |                                                                 (4)
   | y3 = lambda * (x1 - x3) - y1 (mod p),
   
                   y1 - y2
   where lambda = -------- (mod p).
                   x1 - x2

If x1 = x2 and y1 = y2 /= 0, then we will define point Q3 coordinates in the following way: 

   | x3 = lambda^2 - x1 * 2 (mod p),
   |                                                                 (5)
   | y3 = lambda * (x1 - x3) - y1 (mod p),
   
                  3 * x1^2 + a
   where lambda = ------------ (mod p)
                     y1 * 2

If x1 = x2 and y1 = -y2 (mod p), then the sum of points Q1 and Q2 is called a zero point O, without determination of its x- and y- coordinates. In this case, point Q2 is called a negative of point Q1. For the zero point, the equalities hold: 

   O + Q = Q + O = Q,                                                (6)

where Q is an arbitrary point of elliptic curve E.

A set of all points of elliptic curve E, including the zero point, forms a finite abelian (commutative) group of order m regarding the introduced addition operation. For m, the following inequalities hold: 

   p + 1 - 2 * sqrt(p) =< m =< p + 1 + 2 * sqrt(p)                   (7)

The point Q is called "a point of multiplicity k", or just "a multiple point of the elliptic curve E", if for some point P, the following equality holds: 

   Q = P + ... + P = k * P                                           (8)
       -----+-----
            k

5.2. Digital Signature Parameters

The digital signature parameters are:

  • prime number p is an elliptic curve modulus.
  • elliptic curve E, defined by its invariant J(E) or by coefficients a, b belonging to GF(p).
  • integer m is an elliptic curve E points group order.
  • prime number q is an order of a cyclic subgroup of the elliptic curve E points group, which satisfies the following conditions:
   | m = nq, n belongs to Z, n >= 1
   |                                                                 (9)
   | 2^254 < q < 2^256 or 2^508 < q < 2^512
  • point P /= O of an elliptic curve E, with coordinates (x_p, y_p), satisfying the equality q * P = O.
   -  hash function h(.):V_all -> V_l, which maps the messages
   
      represented as binary vectors of arbitrary finite length onto
      binary vectors of an l-bit length.  The hash function is defined
      in GOST R 34.11-2012 [GOST3411-2012].
   
      If 2^254 < q < 2^256, then l = 256.
      If 2^508 < q < 2^512, then l = 512.

Every user of the digital signature scheme must have its personal keys:

  • signature key, which is an integer d, satisfying the inequality 0 < d < q;
  • verification key, which is an elliptic curve point Q with coordinates (x_q, y_q), satisfying the equality d * P = Q.

The previously introduced digital signature parameters must satisfy the following requirements:

  • it is necessary that the condition p^t /= 1 (mod q) holds for all integers t = 1, 2, ..., B, where
      B = 31  if 2^254 < q < 2^256, or
      B = 131 if 2^508 < q < 2^512;
  • it is necessary that the inequality m /= p holds;
  • the curve invariant must satisfy the condition J(E) /= 0, 1728.

5.3. Binary Vectors

To determine the digital signature generation and verification processes, it is necessary to map the set of integers onto the set of binary vectors of an l-bit length.

Consider the following binary vector of an l-bit length where low- order bits are placed on the right, and high-order ones are placed on the left: 

   H = (alpha[l-1], ..., alpha[0]), H belongs to V_l                (10)

where alpha[i], i = 0, ..., l-1 are equal to 1 or to 0. The number alpha belonging to Z is mapped onto the binary vector h, if the equality holds: 

   alpha = alpha[0]*2^0 + alpha[1]*2^1 + ... + alpha[l-1]*2^(l-1)   (11)

For two binary vectors H1 and H2: 

   H1 = (alpha[l-1], ..., alpha[0]),
                                                                    (12)
   H2 = (beta[l-1], ..., beta[0]),

which correspond to integers alpha and beta, we define a concatenation (union) operation in the following way: 

   H1||H2 = (alpha[l-1], ..., alpha[0], beta[l-1], ..., beta[0])    (13)

that is a binary vector of 2*l-bit length, consisting of coefficients of the vectors H1 and H2.

On the other hand, the introduced formulae define a way to divide a binary vector H of 2*l-bit length into two binary vectors of l-bit length, where H is the concatenation of the two.

6. Main Processes

In this section, the digital signature generation and verification processes of a user's message are defined.

To realize the processes, it is necessary that all users know the digital signature scheme parameters, which satisfy the requirements of Section 5.2.

Besides, every user must have the signature key d and the verification key Q(x_q, y_q), which also must satisfy the requirements of Section 5.2.

6.1. Digital Signature Generation Process

It is necessary to perform the following actions (steps) to obtain the digital signature for the message M belonging to V_all. This is Algorithm I.

Step 1. Calculate the message hash code M: 

            H = h(M)                                                (14)

Step 2. Calculate an integer alpha, the binary representation of

which is the vector H, and determine: 

            e = alpha (mod q)                                       (15)

If e = 0, then assign e = 1.

Step 3. Generate a random (pseudorandom) integer k, satisfying the

inequality: 

            0 < k < q                                               (16)

Step 4. Calculate the elliptic curve point C = k * P and determine: 

            r = x_C (mod q),                                        (17)

where x_C is the x-coordinate of the point C. If r = 0, return to step 3.

Step 5. Calculate the value: 

            s = (r * d + k * e) (mod q)                             (18)

If s = 0, return to Step 3.

Step 6. Calculate the binary vectors R and S, corresponding to r and

s, and determine the digital signature zeta = (R || S) as a concatenation of these two binary vectors.

The initial data of this process are the signature key d and the message M to be signed. The output result is the digital signature zeta.

6.2. Digital Signature Verification

To verify the digital signature for the received message M, it is necessary to perform the following actions (steps). This is Algorithm II.

Step 1. Calculate the integers r and s using the received signature

zeta. If the inequalities 0 < r < q, 0 < s < q hold, go to the next step. Otherwise, the signature is invalid.

Step 2. Calculate the hash code of the received message M: 

            H = h(M)                                                (19)

Step 3. Calculate the integer alpha, the binary representation of

which is the vector H, and determine if: 

            e = alpha (mod q)                                       (20)

If e = 0, then assign e = 1.

Step 4. Calculate the value: 

            v = e^(-1) (mod q)                                      (21)

Step 5. Calculate the values: 

            z1 = s * v (mod q), z2 = -r * v (mod q)                 (22)
   
   Step 6.  Calculate the elliptic curve point C = z1 * P + z2 * Q and
            determine:
   
            R = x_C (mod q),                                        (23)

where x_C is x-coordinate of the point.

Step 7. If the equality R = r holds, then the signature is accepted.

Otherwise, the signature is invalid.

The input data of the process are the signed message M, the digital signature zeta, and the verification key Q. The output result is the witness of the signature validity or invalidity.

7. Test Examples (Appendix to GOST R 34.10-2012)

This section is included in GOST R 34.10-2012 as a reference appendix but is not officially mentioned as a part of the standard.

The values given here for the parameters p, a, b, m, q, P, the signature key d, and the verification key Q are recommended only for testing the correctness of actual realizations of the algorithms described in GOST R 34.10-2012.

All numerical values are introduced in decimal and hexadecimal notations. The numbers beginning with 0x are in hexadecimal notation. The symbol "\\" denotes that the number continues on the next line. For example, the notation:

12345\\
67890 

      0x499602D2

represents 1234567890 in decimal and hexadecimal number systems, respectively.

7.1. The Digital Signature Scheme Parameters

The following parameters must be used for digital signature generation and verification (see Section 5.2).

7.1.1. Elliptic Curve Modulus

The following value is assigned to parameter p in this example:

p = 57896044618658097711785492504343953926\\

p = 0x8000000000000000000000000000\\

7.1.2. Elliptic Curve Coefficients

Parameters a and b take the following values in this example: 

   a = 7
   a = 0x7

b = 43308876546767276905765904595650931995\\

b = 0x5FBFF498AA938CE739B8E022FBAFEF40563\\ 

       F6E6A3472FC2A514C0CE9DAE23B7E

7.1.3. Elliptic Curve Points Group Order

Parameter m takes the following value in this example:

m = 5789604461865809771178549250434395392\\

m = 0x80000000000000000000000000000\\ 

       00150FE8A1892976154C59CFC193ACCF5B3

7.1.4. Order of Cyclic Subgroup of Elliptic Curve Points Group

Parameter q takes the following value in this example:

q = 5789604461865809771178549250434395392\\

q = 0x80000000000000000000000000000001\\ 

       50FE8A1892976154C59CFC193ACCF5B3

7.1.5. Elliptic Curve Point Coordinates

Point P coordinates take the following values in this example: 

   x_p = 2
   x_p = 0x2

y_p = 40189740565390375033354494229370597\\

y_p = 0x8E2A8A0E65147D4BD6316030E16D19\\ 

         C85C97F0A9CA267122B96ABBCEA7E8FC8

7.1.6. Signature Key

It is supposed, in this example, that the user has the following signature key d:

d = 554411960653632461263556241303241831\\

d = 0x7A929ADE789BB9BE10ED359DD39A72C\\ 

       11B60961F49397EEE1D19CE9891EC3B28

7.1.7. Verification Key

It is supposed, in this example, that the user has the verification key Q with the following coordinate values:

x_q = 57520216126176808443631405023338071\\

x_q = 0x7F2B49E270DB6D90D8595BEC458B5\\ 

         0C58585BA1D4E9B788F6689DBD8E56FD80B

y_q = 17614944419213781543809391949654080\\

y_q = 0x26F1B489D6701DD185C8413A977B3\\ 

         CBBAF64D1C593D26627DFFB101A87FF77DA

7.2. Digital Signature Process (Algorithm I)

Suppose that after Steps 1-3 in Algorithm I (Section 6.1) are performed, the following numerical values are obtained:

e = 2079889367447645201713406156150827013\\

e = 0x2DFBC1B372D89A1188C09C52E0EE\\ 

       C61FCE52032AB1022E8E67ECE6672B043EE5

k = 538541376773484637314038411479966192\\

k = 0x77105C9B20BCD3122823C8CF6FCC\\ 

       7B956DE33814E95B7FE64FED924594DCEAB3

And the multiple point C = k * P has the coordinates:

x_C = 297009809158179528743712049839382569\\

x_C = 0x41AA28D2F1AB148280CD9ED56FED\\ 

         A41974053554A42767B83AD043FD39DC0493

y[C] = 328425352786846634770946653225170845\\

y[C] = 0x489C375A9941A3049E33B34361DD\\ 

          204172AD98C3E5916DE27695D22A61FAE46E

Parameter r = x_C (mod q) takes the value:

r = 297009809158179528743712049839382569\\

r = 0x41AA28D2F1AB148280CD9ED56FED\\ 

       A41974053554A42767B83AD043FD39DC0493

Parameter s = (r * d + k * e)(mod q) takes the value:

s = 57497340027008465417892531001914703\\

s = 0x1456C64BA4642A1653C235A98A602\\ 

       49BCD6D3F746B631DF928014F6C5BF9C40

7.3. Verification Process of Digital Signature (Algorithm II)

Suppose that after Steps 1-3 in Algorithm II (Section 6.2) are performed, the following numerical value is obtained:

e = 2079889367447645201713406156150827013\\

e = 0x2DFBC1B372D89A1188C09C52E0EE\\ 

       C61FCE52032AB1022E8E67ECE6672B043EE5

And the parameter v = e^(-1) (mod q) takes the value:

v = 176866836059344686773017138249002685\\

v = 0x271A4EE429F84EBC423E388964555BB\\ 

       29D3BA53C7BF945E5FAC8F381706354C2
   
   The parameters z1 = s * v (mod q) and z2 = -r * v (mod q) take the
   values:

z1 = 376991675009019385568410572935126561\\

z1 = 0x5358F8FFB38F7C09ABC782A2DF2A\\ 

        3927DA4077D07205F763682F3A76C9019B4F

z2 = 141719984273434721125159179695007657\\

z2 = 0x3221B4FBBF6D101074EC14AFAC2D4F7\\ 

        EFAC4CF9FEC1ED11BAE336D27D527665

The point C = z1 * P + z2 * Q has the coordinates:

x_C = 2970098091581795287437120498393825699\\

x_C = 0x41AA28D2F1AB148280CD9ED56FED\\ 

         A41974053554A42767B83AD043FD39DC0493

y[C] = 3284253527868466347709466532251708450\\

y[C] = 0x489C375A9941A3049E33B34361DD\\ 

          204172AD98C3E5916DE27695D22A61FAE46E

Then the parameter R = x_C (mod q) takes the value:

R = 2970098091581795287437120498393825699\\

R = 0x41AA28D2F1AB148280CD9ED56FED\\ 

       A41974053554A42767B83AD043FD39DC0493

Since the equality R = r holds, the digital signature is accepted.

8. Security Considerations

This entire document is about security considerations.

9. References

9.1. Normative References

   [GOST3410-2001]  "Information technology.  Cryptographic data
                    security.  Signature and verification processes of
                    [electronic] digital signature", GOST R 34.10-2001,
                    Gosudarstvennyi Standard of Russian Federation,
                    Government Committee of Russia for Standards, 2001.
                    (In Russian)
   
   [GOST3410-2012]  "Information technology.  Cryptographic data
                    security.  Signature and verification processes of
                    [electronic] digital signature", GOST R 34.10-2012,
                    Federal Agency on Technical Regulating and
                    Metrology, 2012.
   
   [GOST3411-2012]  "Information technology.  Cryptographic Data
                    Security.  Hashing function", GOST R 34.11-2012,
                    Federal Agency on Technical Regulating and
                    Metrology, 2012.
   
   [RFC2119]        Bradner, S., "Key words for use in RFCs to Indicate
                    Requirement Levels", BCP 14, RFC 2119, March 1997.
   
   [RFC4357]        Popov, V., Kurepkin, I., and S. Leontiev,
                    "Additional Cryptographic Algorithms for Use with
                    GOST 28147-89, GOST R 34.10-94, GOST R 34.10-2001,
                    and GOST R 34.11-94 Algorithms", RFC 4357, January
                    2006.

9.2. Informative References

   [ISO2382-2]      ISO, "Data processing - Vocabulary - Part 2:
                    Arithmetic and logic operations", ISO 2382-2, 1976.
   
   [ISO9796-2]      ISO/IEC, "Information technology - Security
                    techniques - Digital signatures giving message
                    recovery - Part 2: Integer factorization based
                    mechanisms", ISO/IEC 9796-2, 2010.
   
   [ISO9796-3]      ISO/IEC, "Information technology - Security
                    techniques - Digital signature schemes giving
                    message recovery - Part 3: Discrete logarithm based
                    mechanisms", ISO/IEC 9796-3, 2006.
   
   [ISO14888-1]     ISO/IEC, "Information technology - Security
                    techniques - Digital signatures with appendix - Part
                    1: General", ISO/IEC 14888-1, 2008.
   
   [ISO14888-2]     ISO/IEC, "Information technology - Security
                    techniques - Digital signatures with appendix - Part
                    2: Integer factorization based mechanisms", ISO/IEC
                    14888-2, 2008.
   
   [ISO14888-3]     ISO/IEC, "Information technology - Security
                    techniques - Digital signatures with appendix - Part
                    3: Discrete logarithm based mechanisms", ISO/IEC
                    14888-3,2006.
   
   [ISO14888-4]     ISO/IEC, "Information technology - Security
                    techniques - Digital signatures with appendix - Part
                    3: Discrete logarithm based mechanisms.  Amendment
                    1.  Elliptic Curve Russian Digital Signature
                    Algorithm, Schnorr Digital Signature Algorithm,
                    Elliptic Curve Schnorr Digital Signature Algorithm,
                    and Elliptic Curve Full Schnorr Digital Signature
                    Algorithm", ISO/IEC 14888-3:2006/Amd 1, 2010.
   
   [ISO10118-1]     ISO/IEC, "Information technology - Security
                    techniques - Hash-functions - Part 1: General",
                    ISO/IEC 10118-1, 2000.
   
   [ISO10118-2]     ISO/IEC, "Information technology - Security
                    techniques - Hash-functions - Part 2: Hash-
                    functions using an n-bit block cipher algorithm",
                    ISO/IEC 10118-2, 2010.
   
   [ISO10118-3]     ISO/IEC, "Information technology - Security
                    techniques - Hash-functions - Part 3: Dedicated
                    hash-functions", ISO/IEC 10118-3, 2004.
   
   [ISO10118-4]     ISO/IEC, "Information technology - Security
                    techniques - Hash-functions - Part 4: Hash-
                    functions using modular arithmetic", ISO/IEC
                    10118-4, 1998.
   
   [RFC5832]        Dolmatov, V., Ed., "GOST R 34.10-2001: Digital
                    Signature Algorithm", RFC 5832, March 2010.
   
   [RFC6986]        Dolmatov, V., Ed., and A. Degtyarev, "GOST R
                    34.11-2012: Hash Function", RFC 6986, August 2013.

Authors' Addresses

   Vasily Dolmatov (editor)
   Cryptocom, Ltd.
   14 Kedrova St., Bldg. 2
   Moscow, 117218
   Russian Federation

EMail: 

          dol@cryptocom.ru
   
   Alexey Degtyarev
   Cryptocom, Ltd.
   14 Kedrova St., Bldg. 2
   Moscow, 117218
   Russian Federation

EMail: 

          alexey@renatasystems.org