Skip to content

README.md

Latest commit

 

History

History
50 lines (37 loc) · 2.96 KB

README.md

File metadata and controls

50 lines (37 loc) · 2.96 KB
Raw

gost28147imit — GOST 28147-89 IMIT MAC + CryptoPro key meshing (RFC 5830 / RFC 4357)

package gost28147imit computes the IMIT (имитовставка / "imitovstavka"), the keyed message-authentication code defined inside GOST 28147-89 and republished as RFC 5830 §8. It is a CBC-MAC built on a 16-round truncation of the GOST 28147-89 block transform, with CryptoPro key meshing (RFC 4357 §2.3.2) applied every 1024 processed bytes.

Import path: github.com/tarantool/go-gostcrypto/gost28147imit

API

Symbol Description
IMIT(key, msg []byte) []byte One-shot MAC: CryptoPro-A S-box, zero IV, CryptoPro key meshing, truncated to the 4-byte TLS tag length (RFC 9189 §4.2). key must be 32 bytes and msg non-empty; both violations panic.
SeqMACBlock(key []byte, sbox gost28147.SBox, block []byte) []byte Runs the 16-round SeqMAC transform of one 8-byte block from a zero initial state, returning the 8-byte result. Exposes the 16-round step that the gost28147 cipher's public Encrypt/Decrypt (always 32 rounds) cannot reach — used by callers that drive their own streaming IMIT (e.g. a TLS record protector) block-by-block. key must be 32 bytes, block exactly 8; both panic otherwise.

There is no exported type: gost28147imit is a pair of pure functions, not a streaming accumulator. IMIT is one-shot only, over the CryptoPro-A S-box; it does not implement hash.Hash and has no Write/Sum/Reset. A caller that needs a streaming MAC (persisting state across writes, or a different S-box) drives SeqMACBlock directly and keeps its own chaining state, key-meshing counter, and finalization logic — as the sibling gostls TLS module's record protector does.

Usage

import "github.com/tarantool/go-gostcrypto/gost28147imit"

key := make([]byte, 32) // 32-byte GOST 28147-89 key
tag := gost28147imit.IMIT(key, message) // 4-byte TLS-truncated IMIT

For a non-default S-box, a non-zero IV, or persistence across multiple messages (streaming), build the MAC from SeqMACBlock directly — see DESIGN.md for the chaining, padding, and key-meshing rules that must be reproduced around it.

Standards

  • RFC 5830 §8 — "Generation of an Imitovstavka (MAC)"; the IMIT construction over the GOST 28147-89 block core (§5–§7 of the same RFC).
  • RFC 4357 §2.3.2 — CryptoPro key meshing; §6.3 — CryptoPro KEK wrap (the non-zero-IV IMIT use handled outside this package).
  • RFC 9189 §4.2 — GOST cipher suites for TLS 1.2: the IMIT-4 truncation this package's IMIT implements.
  • RFC 5246 §6.2.3.1 — TLS 1.2 per-record MAC input framing, assembled by the record-layer protector, not by this package.
  • GOST 28147-89 — the Russian national standard itself, republished in English as RFC 5830.

Documentation

  • DESIGN.md — algorithm description, specification, implementation notes, and test vectors.