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bign-genk: Initial implementation (#1109)

Browse Source 
See §6.3.3 of https://apmi.bsu.by/assets/files/std/bign-spec295.pdf
This commit is contained in:
Alexandr Kitaev
2026-03-27 19:37:22 +03:00
committed by GitHub
parent ecfc95ebc4
commit 32e80942ca
10 changed files with 727 additions and 0 deletions
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.github/workflows/bign-genk.yml
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name: bign-genk
on:
pull_request:
paths:
- "bign-genk/**"
- "Cargo.*"
push:
branches: master
defaults:
run:
working-directory: bign-genk
env:
CARGO_INCREMENTAL: 0
RUSTFLAGS: "-Dwarnings"
# Cancels CI jobs when new commits are pushed to a PR branch
concurrency:
group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
cancel-in-progress: true
jobs:
build:
runs-on: ubuntu-latest
strategy:
matrix:
target:
- thumbv7em-none-eabi
- wasm32-unknown-unknown
rust:
- 1.85.0 # MSRV
- stable
steps:
- uses: actions/checkout@v5
- uses: dtolnay/rust-toolchain@master
with:
toolchain: ${{ matrix.rust }}
targets: ${{ matrix.target }}
- run: cargo build --no-default-features --release --target ${{ matrix.target }}
test:
runs-on: ubuntu-latest
strategy:
matrix:
rust:
- 1.85.0 # MSRV
- stable
steps:
- uses: actions/checkout@v5
- uses: dtolnay/rust-toolchain@master
with:
toolchain: ${{ matrix.rust }}
- run: cargo check --all-features
- run: cargo test
Cargo.lock
Generated
+37
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@@ -67,6 +67,43 @@ version = "1.8.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "2af50177e190e07a26ab74f8b1efbfe2ef87da2116221318cb1c2e82baf7de06"
[[package]]
name = "belt-block"
version = "0.1.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "d9aa1eef3994e2ccd304a78fe3fea4a73e5792007f85f09b79bb82143ca5f82b"
[[package]]
name = "belt-block"
version = "0.2.0-rc.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "0e3b1e9d1ad19c345095575076767febd525013fc5782276a21069901815ea45"
dependencies = [
"cipher",
]
[[package]]
name = "belt-hash"
version = "0.2.0-rc.5"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "c56883a45783acff1ccdf0903f38b8688363e633d3c9a199c2063f0cc946832b"
dependencies = [
"belt-block 0.1.2",
"digest 0.11.1",
]
[[package]]
name = "bign-genk"
version = "0.5.0-rc.3"
dependencies = [
"belt-block 0.2.0-rc.3",
"belt-hash",
"cipher",
"digest 0.11.1",
"hex-literal",
"subtle",
]
[[package]]
name = "bit-set"
version = "0.8.0"
Cargo.toml
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@@ -1,6 +1,7 @@
[workspace]
resolver = "2"
members = [
"bign-genk",
"dsa",
"ecdsa",
"ed448",
@@ -27,3 +28,4 @@ ml-dsa = { path = "./ml-dsa" }
rfc6979 = { path = "./rfc6979" }
slh-dsa = { path = "./slh-dsa" }
xmss = { path = "./xmss" }
bign-genk = { path = "./bign-genk" }
bign-genk/CHANGELOG.md
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# Changelog
All notable changes to this project will be documented in this file.
The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
### 0.5.0 (XXXX-XX-XX)
- Initial release
[#1109](https://github.com/RustCrypto/signatures/pull/1109)
bign-genk/Cargo.toml
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[package]
name = "bign-genk"
version = "0.5.0-rc.3"
description = """
Pure Rust implementation of bign-genk algorithm from STB 34.101.45: Deterministic Usage of the
Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA)
"""
authors = ["RustCrypto Developers"]
license = "Apache-2.0 OR MIT"
homepage = "https://github.com/RustCrypto/signatures/tree/master/bign-genk"
repository = "https://github.com/RustCrypto/signatures"
readme = "README.md"
categories = ["cryptography", "no-std"]
keywords = ["dsa", "ecdsa", "signature", "bign"]
edition = "2024"
rust-version = "1.85"
[dependencies]
cipher = { version = "0.5", default-features = false }
digest = { version = "0.11", default-features = false, features = ["oid"] }
subtle = { version = "2", default-features = false }
[dev-dependencies]
hex-literal = "1"
belt-block = "0.2.0-rc.3"
belt-hash = "0.2.0-rc.5"
bign-genk/LICENSE-APACHE
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bign-genk/LICENSE-MIT
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Copyright (c) 2018-2025 RustCrypto Developers
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bign-genk/README.md
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# [RustCrypto]: STB 34.101.45 Deterministic Signatures
[![crate][crate-image]][crate-link]
[![Docs][docs-image]][docs-link]
[![Build Status][build-image]][build-link]
![Apache2/MIT licensed][license-image]
![MSRV][rustc-image]
[![Project Chat][chat-image]][chat-link]
Pure Rust implementation of `bign-genk` from STB 34.101.45: Deterministic Usage of the
Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA).
Algorithm described in STB 34.101.45-2013 § 6.3:
<https://apmi.bsu.by/assets/files/std/bign-spec295.pdf>
[Documentation][docs-link]
## Minimum Supported Rust Version
This crate requires **Rust 1.85** at a minimum.
We may change the MSRV in the future, but it will be accompanied by a minor
version bump.
## License
All crates licensed under either of
* [Apache License, Version 2.0](https://www.apache.org/licenses/LICENSE-2.0)
* [MIT license](https://opensource.org/licenses/MIT)
at your option.
### Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.
[//]: # (badges)
[crate-image]: https://img.shields.io/crates/v/bign-genk?logo=rust
[crate-link]: https://crates.io/crates/bign-genk
[docs-image]: https://docs.rs/bign-genk/badge.svg
[docs-link]: https://docs.rs/bign-genk/
[build-image]: https://github.com/RustCrypto/signatures/actions/workflows/bign-genk.yml/badge.svg
[build-link]: https://github.com/RustCrypto/signatures/actions/workflows/bign-genk.yml
[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
[rustc-image]: https://img.shields.io/badge/rustc-1.85+-blue.svg
[chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
[chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260048-signatures
[//]: # (links)
[RustCrypto]: https://github.com/RustCrypto
bign-genk/src/ct.rs
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//! Constant-time helpers.
// TODO(tarcieri): replace this with `crypto-bigint`?
use subtle::{Choice, ConditionallySelectable, ConstantTimeEq};
/// Constant-time test that a given byte slice contains only zeroes.
#[inline]
pub(crate) fn is_zero(n: &[u8]) -> Choice {
let mut ret = Choice::from(1);
for byte in n {
ret.conditional_assign(&Choice::from(0), byte.ct_ne(&0));
}
ret
}
/// Constant-time less than.
///
/// Inputs are interpreted as little endian integers.
pub(crate) fn lt(a: &[u8], b: &[u8]) -> Choice {
debug_assert_eq!(a.len(), b.len());
let mut borrow = 0u16;
for (a_byte, b_byte) in a.iter().zip(b.iter()) {
let diff = (*a_byte as u16)
.wrapping_sub(*b_byte as u16)
.wrapping_sub(borrow);
borrow = (diff >> 8) & 1;
}
Choice::from(borrow as u8)
}
#[cfg(test)]
mod tests {
const A: [u8; 4] = [0, 0, 0, 0];
const B: [u8; 4] = [0, 0, 0, 1];
const C: [u8; 4] = [0xFF, 0, 0, 0];
const D: [u8; 4] = [0xFF, 0, 0, 1];
const E: [u8; 4] = [0xFF, 0xFF, 0xFF, 0xFE];
const F: [u8; 4] = [0xFF, 0xFF, 0xFF, 0xFF];
#[test]
fn ct_is_zero() {
use super::is_zero;
assert_eq!(is_zero(&A).unwrap_u8(), 1);
assert_eq!(is_zero(&B).unwrap_u8(), 0);
}
#[test]
fn ct_lt() {
use super::lt;
assert_eq!(lt(&A, &A).unwrap_u8(), 0);
assert_eq!(lt(&B, &B).unwrap_u8(), 0);
assert_eq!(lt(&C, &C).unwrap_u8(), 0);
assert_eq!(lt(&D, &D).unwrap_u8(), 0);
assert_eq!(lt(&E, &E).unwrap_u8(), 0);
assert_eq!(lt(&F, &F).unwrap_u8(), 0);
assert_eq!(lt(&A, &B).unwrap_u8(), 1);
assert_eq!(lt(&A, &C).unwrap_u8(), 1);
assert_eq!(lt(&B, &A).unwrap_u8(), 0);
assert_eq!(lt(&C, &A).unwrap_u8(), 0);
assert_eq!(lt(&C, &B).unwrap_u8(), 1);
assert_eq!(lt(&B, &D).unwrap_u8(), 1);
assert_eq!(lt(&B, &C).unwrap_u8(), 0);
assert_eq!(lt(&D, &B).unwrap_u8(), 0);
assert_eq!(lt(&C, &D).unwrap_u8(), 1);
assert_eq!(lt(&C, &E).unwrap_u8(), 1);
assert_eq!(lt(&D, &C).unwrap_u8(), 0);
assert_eq!(lt(&E, &C).unwrap_u8(), 0);
assert_eq!(lt(&E, &F).unwrap_u8(), 1);
assert_eq!(lt(&F, &E).unwrap_u8(), 0);
}
}
bign-genk/src/lib.rs
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#![no_std]
#![doc = include_str!("../README.md")]
#![forbid(unsafe_code, clippy::unwrap_used)]
#![warn(missing_docs, rust_2018_idioms, unreachable_pub)]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/RustCrypto/media/8f1a9894/logo.svg",
html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/media/8f1a9894/logo.svg"
)]
//! ## Usage
//!
//! See also: the documentation for the [`generate_k`] function.
//!
//! ```
//! use hex_literal::hex;
//! use bign_genk::consts::U32;
//! use belt_hash::{Digest, BeltHash};
//! use belt_block::BeltBlock;
//!
//! // BIGN P-256 field modulus
//! const BIGNP256_MODULUS: [u8; 32] =
//! hex!("FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF C95E2EAB 40309C49 56129C2E F129D6CC");
//!
//! // Public key for STB 34.101.45 Bign P256/BeltHash test case
//! const KEY: [u8; 32] =
//! hex!("1F66B5B8 4B733967 4533F032 9C74F218 34281FED 0732429E 0C79235F C273E269");
//!
//! // Test message for STB 34.101.45 Bign P256/BeltHash test case
//! const MSG: [u8; 13] =
//! hex!("B194BAC8 0A08F53B 366D008E 58");
//!
//! // Expected K for STB 34.101.45 Bign P256/BeltHash test case
//! const EXPECTED_K: [u8; 32] =
//! hex!("829614D8 411DBBC4 E1F2471A 40045864 40FD8C95 53FAB6A1 A45CE417 AE97111E");
//!
//! let h = BeltHash::digest(MSG);
//! let k = bign_genk::generate_k::<BeltHash, BeltBlock, U32>(
//! &KEY.into(),
//! &BIGNP256_MODULUS.into(),
//! &h,
//! &[],
//! );
//! assert_eq!(k.as_slice(), &EXPECTED_K);
//! ```
pub use cipher::Array;
pub use cipher::typenum::consts;
use cipher::{BlockCipherEncrypt, BlockSizeUser, KeyInit, array::ArraySize, typenum::Unsigned};
use digest::Digest;
use digest::const_oid::AssociatedOid;
mod ct;
type BlockArray<C> = <<C as BlockSizeUser>::BlockSize as ArraySize>::ArrayType<u8>;
/// Deterministically generate ephemeral scalar `k`.
///
/// Accepts the following parameters and inputs:
///
/// - `x`: secret key
/// - `q`: field modulus
/// - `h`: hash/digest of an input message: must be reduced modulo `q` in advance
/// - `data`: additional associated data, e.g., CSRNG output used as added entropy
#[inline]
pub fn generate_k<D, C, N>(
x: &Array<u8, N>,
q: &Array<u8, N>,
h: &Array<u8, N>,
data: &[u8],
) -> Array<u8, N>
where
D: BlockSizeUser + Clone + Digest + AssociatedOid,
C: BlockSizeUser + Clone + BlockCipherEncrypt + KeyInit,
N: ArraySize,
BlockArray<C>: Copy,
{
let mut k = Array::default();
generate_k_mut::<D, C>(x, q, h, data, &mut k);
k
}
/// Deterministically generate ephemeral scalar `k` by writing it into the provided output buffer.
///
/// This is an API that accepts dynamically sized inputs intended for use cases where the sizes
/// are determined at runtime, such as the legacy Digital Signature Algorithm (DSA).
///
/// Accepts the following parameters and inputs:
///
/// - `x`: secret key
/// - `q`: field modulus
/// - `h`: hash/digest of an input message: must be reduced modulo `q` in advance
/// - `data`: additional associated data, e.g., CSRNG output used as added entropy
#[inline]
pub fn generate_k_mut<D, C>(x: &[u8], q: &[u8], h: &[u8], data: &[u8], k: &mut [u8])
where
D: BlockSizeUser + Clone + Digest + AssociatedOid,
C: BlockSizeUser + Clone + BlockCipherEncrypt + KeyInit,
BlockArray<C>: Copy,
{
let len = k.len();
assert_eq!(len, x.len());
assert_eq!(len, q.len());
assert_eq!(len, h.len());
assert!(len == 32 || len == 48 || len == 64);
// n = ℓ/64 (2, 3 or 4)
let n = len / C::BlockSize::USIZE;
// 2: θ ← belt-hash(OID(h) ‖ ⟨d⟩ ‖ t)
let mut hasher: D = Digest::new();
hasher.update([0x06, (D::OID.len() - 1) as u8]);
hasher.update(D::OID);
hasher.update(x);
hasher.update(data);
let theta = hasher.finalize();
// belt-block(θ)
let cipher = C::new_from_slice(&theta).expect("Invalid key length");
// 3. r ← H
// r = r₁ ‖ r₂ ‖ ... ‖ r_n, where r_i ∈ {0,1}^128
let mut r = [Array::<u8, C::BlockSize>::default(); 4];
for (i, chunk) in h.chunks(C::BlockSize::USIZE).enumerate().take(n) {
r[i][..chunk.len()].copy_from_slice(chunk);
}
// 4.
let mut i = 1u32;
loop {
let s = match n {
2 => {
// 4.1) s ← r₁
r[0]
}
3 => {
// 4.2.a) s ← r₁ ⊕ r₂
let s = xor_blocks::<C>(&r[0], &r[1]);
// 4.2.b) r₁ ← r₂
r[0] = r[1];
s
}
4 => {
// 4.3.a) s ← r₁ ⊕ r₂ ⊕ r₃
let mut s = xor_blocks::<C>(&r[0], &r[1]);
xor_assign(&mut s, &r[2]);
// 4.3.b) r₁ ← r₂
r[0] = r[1];
// 4.3.c) r₂ ← r₃
r[1] = r[2];
s
}
_ => unreachable!(),
};
// 4.4: r_(n-1) ← belt-block(s, θ) ⊕ r_n ⊕ ⟨i⟩_128
let mut encrypted = s;
cipher.encrypt_block(&mut encrypted);
// ⊕ r_n
xor_assign(&mut encrypted, &r[n - 1]);
// ⊕ ⟨i⟩_128
xor_assign(&mut encrypted, &i.to_le_bytes());
// r_(n-1)
r[n - 2] = encrypted;
// 4.5: r_n ← s
r[n - 1] = s;
// 4.6: Check every 2n iterations
if i % (2 * n as u32) == 0 {
for (j, chunk) in r.iter().enumerate().take(n) {
k[j * C::BlockSize::USIZE..(j + 1) * C::BlockSize::USIZE].copy_from_slice(chunk);
}
// Assert: k ∈ {1, 2, ..., q-1}
if (!ct::is_zero(k) & ct::lt(k, q)).into() {
return; // 5-6: k ← r, return
}
}
i = i.wrapping_add(1);
}
}
/// XOR two blocks of arbitrary size
#[inline]
fn xor_blocks<C>(
a: &Array<u8, C::BlockSize>,
b: &Array<u8, C::BlockSize>,
) -> Array<u8, C::BlockSize>
where
C: BlockSizeUser,
BlockArray<C>: Copy,
{
let mut result = *a;
xor_assign(&mut result, b);
result
}
/// XOR-assignment
#[inline]
fn xor_assign(a: &mut [u8], b: &[u8]) {
for (a_byte, b_byte) in a.iter_mut().zip(b.iter()) {
*a_byte ^= b_byte;
}
}
#[cfg(test)]
mod tests {
use super::*;
use belt_block::{BeltBlock, cipher::typenum::U32};
use belt_hash::BeltHash;
use hex_literal::hex;
/// Table 7 appendix G STB 34.101.45
#[test]
fn stb_table_g7() {
let d = hex!("1F66B5B8 4B733967 4533F032 9C74F218 34281FED 0732429E 0C79235F C273E269");
let q = hex!("FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF C95E2EAB 40309C49 56129C2E F129D6CC");
let h = hex!("9D02EE44 6FB6A29F E5C982D4 B13AF9D3 E90861BC 4CEF27CF 306BFB0B 174A154A");
let t = hex!("BE329713 43FC9A48 A02A885F 194B09A1 7ECDA4D0 1544AF");
let expected_k =
hex!("7ADC8713 283EBFA5 47A2AD9C DFB245AE 0F7B968D F0F91CB7 85D1F932 A3583107");
let k = generate_k::<BeltHash, BeltBlock, U32>(&d.into(), &q.into(), &h.into(), &t);
assert_eq!(k.as_slice(), &expected_k);
}
}