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Independent Submission                                  V. Dolmatov, Ed.
Request for Comments: 8891                          JSC "NPK Kryptonite"
Updates: 5830                                               D. Baryshkov
Category: Informational                                     Auriga, Inc.
ISSN: 2070-1721                                           September 2020

GOST R 34.12-2015: Block Cipher "Magma"

Abstract

In addition to a new cipher with a block length of n=128 bits (referred to as "Kuznyechik" and described in RFC 7801), Russian Federal standard GOST R 34.12-2015 includes an updated version of the block cipher with a block length of n=64 bits and key length of k=256 bits, which is also referred to as "Magma". The algorithm is an updated version of an older block cipher with a block length of n=64 bits described in GOST 28147-89 (RFC 5830). This document is intended to be a source of information about the updated version of the 64-bit cipher. It may facilitate the use of the block cipher in Internet applications by providing information for developers and users of the GOST 64-bit cipher with the revised version of the cipher for encryption and decryption.

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 candidates for any level of Internet Standard; see Section 2 of RFC 7841.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8891.

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Table of Contents

   1.  Introduction
   2.  General Information
   3.  Definitions and Notation
     3.1.  Definitions
     3.2.  Notation
   4.  Parameter Values
     4.1.  Nonlinear Bijection
     4.2.  Transformations
     4.3.  Key Schedule
   5.  Basic Encryption Algorithm
     5.1.  Encryption
     5.2.  Decryption
   6.  IANA Considerations
   7.  Security Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Appendix A.  Test Examples
     A.1.  Transformation t
     A.2.  Transformation g
     A.3.  Key Schedule
     A.4.  Test Encryption
     A.5.  Test Decryption
   Appendix B.  Background
   Authors' Addresses

1. Introduction

The Russian Federal standard [GOSTR3412-2015] specifies basic block ciphers used as cryptographic techniques for information processing and information protection, including the provision of confidentiality, authenticity, and integrity of information during information transmission, processing, and storage in computer-aided systems.

The cryptographic algorithms defined in this specification are designed both for hardware and software implementation. They comply with modern cryptographic requirements and put no restrictions on the confidentiality level of the protected information.

This document is intended to be a source of information about the updated version of the 64-bit cipher. It may facilitate the use of the block cipher in Internet applications by providing information for developers and users of a GOST 64-bit cipher with the revised version of the cipher for encryption and decryption.

2. General Information

The Russian Federal standard [GOSTR3412-2015] 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). GOST R 34.12-2015 was approved and introduced by Decree #749 of the Federal Agency on Technical Regulating and Metrology on June 19, 2015.

Terms and concepts in the specification comply with the following international standards: 

   *  ISO/IEC 10116 [ISO-IEC10116]
   
   *  series of standards ISO/IEC 18033 [ISO-IEC18033-1][ISO-IEC18033-3]

3. Definitions and Notation

The following terms and their corresponding definitions are used in the specification.

3.1. Definitions

   encryption algorithm:  process that transforms plaintext into
      ciphertext (Clause 2.19 of [ISO-IEC18033-1])
   
   decryption algorithm:  process that transforms ciphertext into
      plaintext (Clause 2.14 of [ISO-IEC18033-1])
   
   basic block cipher:  block cipher that, for a given key, provides a
      single invertible mapping of the set of fixed-length plaintext
      blocks into ciphertext blocks of the same length
   
   block:  string of bits of a defined length (Clause 2.6 of
      [ISO-IEC18033-1])
   
   block cipher:  symmetric encipherment system with the property that
      the encryption algorithm operates on a block of plaintext -- i.e.,
      a string of bits of a defined length -- to yield a block of
      ciphertext (Clause 2.7 of [ISO-IEC18033-1])

Note: In GOST R 34.12-2015, it is established that the terms "block cipher" and "block encryption algorithm" are synonyms. 

   encryption:  reversible transformation of data by a cryptographic
      algorithm to produce ciphertext -- i.e., to hide the information
      content of the data (Clause 2.18 of [ISO-IEC18033-1])
   
   round key:  sequence of symbols that is calculated from the key and
      controls a transformation for one round of a block cipher
   
   key:  sequence of symbols that controls the operation of a
      cryptographic transformation (e.g., encipherment, decipherment)
      (Clause 2.21 of [ISO-IEC18033-1])

Note:

In GOST R 34.12-2015, the key must be a binary sequence. 

   plaintext:  unencrypted information (Clause 3.11 of [ISO-IEC10116])
   
   key schedule:  calculation of round keys from the key,
   
   decryption:  reversal of a corresponding encipherment (Clause 2.13 of
      [ISO-IEC18033-1])
   
   symmetric cryptographic technique:  cryptographic technique that uses
      the same secret key for both the originator's and the recipient's
      transformation (Clause 2.32 of [ISO-IEC18033-1])
   
   cipher:  alternative term for encipherment system (Clause 2.20 of
      [ISO-IEC18033-1])
   
   ciphertext:  data that has been transformed to hide its information
      content (Clause 3.3 of [ISO-IEC10116])

3.2. Notation

The following notation is used in the specification:

V* the set of all binary vector strings of a finite length

(hereinafter referred to as the strings), including the empty string 

   V_s  the set of all binary strings of length s, where s is a
      nonnegative integer; substrings and string components are
      enumerated from right to left, starting from zero
   
   U[*]W  direct (Cartesian) product of two sets U and W
   
   |A|  the number of components (the length) of a string A belonging to
      V* (if A is an empty string, then |A| = 0)
   
   A||B  concatenation of strings A and B both belonging to V* -- i.e.,
      a string from V_(|A|+|B|), where the left substring from V_|A| is
      equal to A and the right substring from V_|B| is equal to B
   
   A<<<_11  cyclic rotation of string A belonging to V_32 by 11
      components in the direction of components having greater indices

Z_(2^n) ring of residues modulo 2^n

(xor) exclusive-or of two binary strings of the same length 

   [+]  addition in the ring Z_(2^32)
   
   Vec_s: Z_(2^s) -> V_s  bijective mapping that maps an element from
      ring Z_(2^s) into its binary representation; i.e., for an element
      z of the ring Z_(2^s), represented by the residue z_0 + (2*z_1) +
      ... + (2^(s-1)*z_(s-1)), where z_i in {0, 1}, i = 0, ..., n-1, the
      equality Vec_s(z) = z_(s-1)||...||z_1||z_0 holds

Int_s: V_s -> Z_(2^s) the mapping inverse to the mapping Vec_s, 

      i.e., Int_s = Vec_s^(-1)
   
   PS  composition of mappings, where the mapping S applies first
   
   P^s  composition of mappings P^(s-1) and P, where P^1=P

4. Parameter Values

4.1. Nonlinear Bijection

The bijective nonlinear mapping is a set of substitutions:

Pi_i = Vec_4 Pi'_i Int_4: V_4 -> V_4, 

   where

Pi'_i:

Z_(2^4) -> Z_(2^4), i = 0, 1, ..., 7.

The values of the substitution Pi' are specified below as arrays.

Pi'_i = (Pi'_i(0), Pi'_i(1), ... , Pi'_i(15)), i = 0, 1, ..., 7: 

   Pi'_0 = (12, 4, 6, 2, 10, 5, 11, 9, 14, 8, 13, 7, 0, 3, 15, 1);
   Pi'_1 = (6, 8, 2, 3, 9, 10, 5, 12, 1, 14, 4, 7, 11, 13, 0, 15);
   Pi'_2 = (11, 3, 5, 8, 2, 15, 10, 13, 14, 1, 7, 4, 12, 9, 6, 0);
   Pi'_3 = (12, 8, 2, 1, 13, 4, 15, 6, 7, 0, 10, 5, 3, 14, 9, 11);
   Pi'_4 = (7, 15, 5, 10, 8, 1, 6, 13, 0, 9, 3, 14, 11, 4, 2, 12);
   Pi'_5 = (5, 13, 15, 6, 9, 2, 12, 10, 11, 7, 8, 1, 4, 3, 14, 0);
   Pi'_6 = (8, 14, 2, 5, 6, 9, 1, 12, 15, 4, 11, 0, 13, 10, 3, 7);
   Pi'_7 = (1, 7, 14, 13, 0, 5, 8, 3, 4, 15, 10, 6, 9, 12, 11, 2);

4.2. Transformations

The following transformations are applicable for encryption and decryption algorithms:

t: 

      V_32 -> V_32
      t(a) = t(a_7||...||a_0) = Pi_7(a_7)||...||Pi_0(a_0), where
      a=a_7||...||a_0 belongs to V_32, a_i belongs to V_4, i=0, 1, ...,
      7.
   
   g[k]: V_32 -> V_32
      g[k](a) = (t(Vec_32(Int_32(a) [+] Int_32(k)))) <<<_11, where k, a
      belong to V_32
   
   G[k]: V_32[*]V_32 -> V_32[*]V_32
      G[k](a_1, a_0) = (a_0, g[k](a_0) (xor) a_1), where k, a_0, a_1
      belong to V_32
   
   G^*[k]: V_32[*]V_32 -> V_64
      G^*[k](a_1, a_0) = (g[k](a_0) (xor) a_1) || a_0, where k, a_0, a_1
      belong to V_32.

4.3. Key Schedule

   Round keys K_i belonging to V_32, i=1, 2, ..., 32 are derived from
   key K = k_255||...||k_0 belonging to V_256, k_i belongs to V_1, i=0,
   1, ..., 255, as follows:
   
   K_1 = k_255||...||k_224;
   K_2 = k_223||...||k_192;
   K_3 = k_191||...||k_160;
   K_4 = k_159||...||k_128;
   K_5 = k_127||...||k_96;
   K_6 = k_95||...||k_64;
   K_7 = k_63||...||k_32;
   K_8 = k_31||...||k_0;
   K_(i+8) = K_i, i = 1, 2, ..., 8;
   K_(i+16) = K_i, i = 1, 2, ..., 8;
   K_(i+24) = K_(9-i), i = 1, 2, ..., 8.

5. Basic Encryption Algorithm

5.1. Encryption

   Depending on the values of round keys K_1,...,K_32, the encryption
   algorithm is a substitution E_(K_1,...,K_32) defined as follows:
   
   E_(K_1,...,K_32)(a)=G^*[K_32]G[K_31]...G[K_2]G[K_1](a_1, a_0),

where a=(a_1, a_0) belongs to V_64, and a_0, a_1 belong to V_32.

5.2. Decryption

   Depending on the values of round keys K_1,...,K_32, the decryption
   algorithm is a substitution D_(K_1,...,K_32) defined as follows:
   
   D_(K_1,...,K_32)(a)=G^*[K_1]G[K_2]...G[K_31]G[K_32](a_1, a_0),

where a=(a_1, a_0) belongs to V_64, and a_0, a_1 belong to V_32.

6. IANA Considerations

This document has no IANA actions.

7. Security Considerations

This entire document is about security considerations.

Unlike [RFC5830] (GOST 28147-89), but like [RFC7801], this specification does not define exact block modes that should be used together with the updated Magma cipher. One is free to select block modes depending on the protocol and necessity.

8. References

8.1. Normative References

[GOSTR3412-2015]

Federal Agency on Technical Regulating and Metrology, "Information technology. Cryptographic data security. Block ciphers.", GOST R 34.12-2015, 2015. 

   [RFC5830]  Dolmatov, V., Ed., "GOST 28147-89: Encryption, Decryption,
              and Message Authentication Code (MAC) Algorithms",
              RFC 5830, DOI 10.17487/RFC5830, March 2010,
              <https://www.rfc-editor.org/info/rfc5830>.
   
   [RFC7801]  Dolmatov, V., Ed., "GOST R 34.12-2015: Block Cipher
              "Kuznyechik"", RFC 7801, DOI 10.17487/RFC7801, March 2016,
              <https://www.rfc-editor.org/info/rfc7801>.

8.2. Informative References

[GOST28147-89]

Government Committee of the USSR for Standards, "Cryptographic Protection for Data Processing System, GOST 28147-89, Gosudarstvennyi Standard of USSR", 1989.

[ISO-IEC10116] 

              ISO/IEC, "Information technology -- Security techniques --
              Modes of operation for an n-bit block cipher", ISO/
              IEC 10116, 2017.

[ISO-IEC18033-1] 

              ISO/IEC, "Information technology -- Security techniques --
              Encryption algorithms -- Part 1: General", ISO/
              IEC 18033-1:2015, 2015.

[ISO-IEC18033-3] 

              ISO/IEC, "Information technology -- Security techniques --
              Encryption algorithms -- Part 3: Block ciphers", ISO/
              IEC 18033-3:2010, 2010.
   
   [RFC7836]  Smyshlyaev, S., Ed., Alekseev, E., Oshkin, I., Popov, V.,
              Leontiev, S., Podobaev, V., and D. Belyavsky, "Guidelines
              on the Cryptographic Algorithms to Accompany the Usage of
              Standards GOST R 34.10-2012 and GOST R 34.11-2012",
              RFC 7836, DOI 10.17487/RFC7836, March 2016,
              <https://www.rfc-editor.org/info/rfc7836>.

Appendix A. Test Examples

This section is for information only and is not a normative part of the specification.

A.1. Transformation t

   t(fdb97531) = 2a196f34,
   t(2a196f34) = ebd9f03a,
   t(ebd9f03a) = b039bb3d,
   t(b039bb3d) = 68695433.

A.2. Transformation g

   g[87654321](fedcba98) = fdcbc20c,
   g[fdcbc20c](87654321) = 7e791a4b,
   g[7e791a4b](fdcbc20c) = c76549ec,
   g[c76549ec](7e791a4b) = 9791c849.

A.3. Key Schedule

With key set to

K = ffeeddccbbaa99887766554433221100f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff,

the following round keys are generated:

K_1 = ffeeddcc,
K_2 = bbaa9988,
K_3 = 77665544,
K_4 = 33221100,
K_5 = f0f1f2f3,
K_6 = f4f5f6f7,
K_7 = f8f9fafb,
K_8 = fcfdfeff,

K_9 = ffeeddcc,
K_10 = bbaa9988,
K_11 = 77665544,
K_12 = 33221100,
K_13 = f0f1f2f3,
K_14 = f4f5f6f7,
K_15 = f8f9fafb,
K_16 = fcfdfeff,

K_17 = ffeeddcc,
K_18 = bbaa9988,
K_19 = 77665544,
K_20 = 33221100,
K_21 = f0f1f2f3,
K_22 = f4f5f6f7,
K_23 = f8f9fafb,
K_24 = fcfdfeff,

K_25 = fcfdfeff,
K_26 = f8f9fafb,
K_27 = f4f5f6f7,
K_28 = f0f1f2f3,
K_29 = 33221100,
K_30 = 77665544,
K_31 = bbaa9988,
K_32 = ffeeddcc.

A.4. Test Encryption

In this test example, encryption is performed on the round keys specified in Appendix A.3. Let the plaintext be

a = fedcba9876543210, 

   then
   
   (a_1, a_0) = (fedcba98, 76543210),
   G[K_1](a_1, a_0) = (76543210, 28da3b14),
   G[K_2]G[K_1](a_1, a_0) = (28da3b14, b14337a5),
   G[K_3]...G[K_1](a_1, a_0) = (b14337a5, 633a7c68),
   G[K_4]...G[K_1](a_1, a_0) = (633a7c68, ea89c02c),
   G[K_5]...G[K_1](a_1, a_0) = (ea89c02c, 11fe726d),
   G[K_6]...G[K_1](a_1, a_0) = (11fe726d, ad0310a4),
   G[K_7]...G[K_1](a_1, a_0) = (ad0310a4, 37d97f25),
   G[K_8]...G[K_1](a_1, a_0) = (37d97f25, 46324615),
   G[K_9]...G[K_1](a_1, a_0) = (46324615, ce995f2a),
   G[K_10]...G[K_1](a_1, a_0) = (ce995f2a, 93c1f449),
   G[K_11]...G[K_1](a_1, a_0) = (93c1f449, 4811c7ad),
   G[K_12]...G[K_1](a_1, a_0) = (4811c7ad, c4b3edca),
   G[K_13]...G[K_1](a_1, a_0) = (c4b3edca, 44ca5ce1),
   G[K_14]...G[K_1](a_1, a_0) = (44ca5ce1, fef51b68),
   G[K_15]...G[K_1](a_1, a_0) = (fef51b68, 2098cd86)
   G[K_16]...G[K_1](a_1, a_0) = (2098cd86, 4f15b0bb),
   G[K_17]...G[K_1](a_1, a_0) = (4f15b0bb, e32805bc),
   G[K_18]...G[K_1](a_1, a_0) = (e32805bc, e7116722),
   G[K_19]...G[K_1](a_1, a_0) = (e7116722, 89cadf21),
   G[K_20]...G[K_1](a_1, a_0) = (89cadf21, bac8444d),
   G[K_21]...G[K_1](a_1, a_0) = (bac8444d, 11263a21),
   G[K_22]...G[K_1](a_1, a_0) = (11263a21, 625434c3),
   G[K_23]...G[K_1](a_1, a_0) = (625434c3, 8025c0a5),
   G[K_24]...G[K_1](a_1, a_0) = (8025c0a5, b0d66514),
   G[K_25]...G[K_1](a_1, a_0) = (b0d66514, 47b1d5f4),
   G[K_26]...G[K_1](a_1, a_0) = (47b1d5f4, c78e6d50),
   G[K_27]...G[K_1](a_1, a_0) = (c78e6d50, 80251e99),
   G[K_28]...G[K_1](a_1, a_0) = (80251e99, 2b96eca6),
   G[K_29]...G[K_1](a_1, a_0) = (2b96eca6, 05ef4401),
   G[K_30]...G[K_1](a_1, a_0) = (05ef4401, 239a4577),
   G[K_31]...G[K_1](a_1, a_0) = (239a4577, c2d8ca3d).

Then the ciphertext is

b = G^*[K_32]G[K_31]...G[K_1](a_1, a_0) = 4ee901e5c2d8ca3d.

A.5. Test Decryption

In this test example, decryption is performed on the round keys specified in Appendix A.3. Let the ciphertext be

b = 4ee901e5c2d8ca3d, 

   then
   
   (b_1, b_0) = (4ee901e5, c2d8ca3d),
   G[K_32](b_1, b_0) = (c2d8ca3d, 239a4577),
   G[K_31]G[K_32](b_1, b_0) = (239a4577, 05ef4401),
   G[K_30]...G[K_32](b_1, b_0) = (05ef4401, 2b96eca6),
   G[K_29]...G[K_32](b_1, b_0) = (2b96eca6, 80251e99),
   G[K_28]...G[K_32](b_1, b_0) = (80251e99, c78e6d50),
   G[K_27]...G[K_32](b_1, b_0) = (c78e6d50, 47b1d5f4),
   G[K_26]...G[K_32](b_1, b_0) = (47b1d5f4, b0d66514),
   G[K_25]...G[K_32](b_1, b_0) = (b0d66514, 8025c0a5),
   G[K_24]...G[K_32](b_1, b_0) = (8025c0a5, 625434c3),
   G[K_23]...G[K_32](b_1, b_0) = (625434c3, 11263a21),
   G[K_22]...G[K_32](b_1, b_0) = (11263a21, bac8444d),
   G[K_21]...G[K_32](b_1, b_0) = (bac8444d, 89cadf21),
   G[K_20]...G[K_32](b_1, b_0) = (89cadf21, e7116722),
   G[K_19]...G[K_32](b_1, b_0) = (e7116722, e32805bc),
   G[K_18]...G[K_32](b_1, b_0) = (e32805bc, 4f15b0bb),
   G[K_17]...G[K_32](b_1, b_0) = (4f15b0bb, 2098cd86),
   G[K_16]...G[K_32](b_1, b_0) = (2098cd86, fef51b68),
   G[K_15]...G[K_32](b_1, b_0) = (fef51b68, 44ca5ce1),
   G[K_14]...G[K_32](b_1, b_0) = (44ca5ce1, c4b3edca),
   G[K_13]...G[K_32](b_1, b_0) = (c4b3edca, 4811c7ad),
   G[K_12]...G[K_32](b_1, b_0) = (4811c7ad, 93c1f449),
   G[K_11]...G[K_32](b_1, b_0) = (93c1f449, ce995f2a),
   G[K_10]...G[K_32](b_1, b_0) = (ce995f2a, 46324615),
   G[K_9]...G[K_32](b_1, b_0) = (46324615, 37d97f25),
   G[K_8]...G[K_32](b_1, b_0) = (37d97f25, ad0310a4),
   G[K_7]...G[K_32](b_1, b_0) = (ad0310a4, 11fe726d),
   G[K_6]...G[K_32](b_1, b_0) = (11fe726d, ea89c02c),
   G[K_5]...G[K_32](b_1, b_0) = (ea89c02c, 633a7c68),
   G[K_4]...G[K_32](b_1, b_0) = (633a7c68, b14337a5),
   G[K_3]...G[K_32](b_1, b_0) = (b14337a5, 28da3b14),
   G[K_2]...G[K_32](b_1, b_0) = (28da3b14, 76543210).

Then the plaintext is

a = G^*[K_1]G[K_2]...G[K_32](b_1, b_0) = fedcba9876543210.

Appendix B. Background

This specification is a translation of relevant parts of the [GOSTR3412-2015] standard. The order of terms in both parts of Section 3 comes from the original text. Combining [RFC7801] with this document will create a complete translation of [GOSTR3412-2015] into English.

Algorithmically, Magma is a variation of the block cipher defined in [RFC5830] ([GOST28147-89]) with the following clarifications and minor modifications: 

   1.  S-BOX set is fixed at id-tc26-gost-28147-param-Z (see Appendix C
       of [RFC7836]);
  1. key is parsed as a single big-endian integer (compared to the little-endian approach used in [GOST28147-89]), which results in different subkey values being used;
  1. data bytes are also parsed as a single big-endian integer (instead of being parsed as little-endian integer).

Authors' Addresses

Vasily Dolmatov (editor)
JSC "NPK Kryptonite"
Spartakovskaya sq., 14, bld 2, JSC "NPK Kryptonite"
Moscow
105082
Russian Federation

Email: 

          vdolmatov@gmail.com

Dmitry Baryshkov
Auriga, Inc.
office 1410
Torfyanaya Doroga, 7F
Saint-Petersburg
197374
Russian Federation

Email: 

          dbaryshkov@gmail.com