Files
serai/crypto/evrf/secq256k1/src/lib.rs
Luke Parker 2bc880e372 Downstream the eVRF libraries from FCMP++
Also adds no-std support to secq256k1 and embedwards25519.
2025-01-29 22:29:40 -05:00

71 lines
2.2 KiB
Rust

#![cfg_attr(docsrs, feature(doc_auto_cfg))]
#![doc = include_str!("../README.md")]
#![cfg_attr(not(feature = "std"), no_std)]
#[cfg(any(feature = "alloc", feature = "std"))]
use std_shims::io::{self, Read};
use generic_array::typenum::{Sum, Diff, Quot, U, U1, U2};
use ciphersuite::group::{ff::PrimeField, Group};
#[macro_use]
mod backend;
mod scalar;
pub use scalar::Scalar;
pub use k256::Scalar as FieldElement;
mod point;
pub use point::Point;
/// Ciphersuite for Secq256k1.
///
/// hash_to_F is implemented with a naive concatenation of the dst and data, allowing transposition
/// between the two. This means `dst: b"abc", data: b"def"`, will produce the same scalar as
/// `dst: "abcdef", data: b""`. Please use carefully, not letting dsts be substrings of each other.
#[derive(Clone, Copy, PartialEq, Eq, Debug, zeroize::Zeroize)]
pub struct Secq256k1;
impl ciphersuite::Ciphersuite for Secq256k1 {
type F = Scalar;
type G = Point;
type H = blake2::Blake2b512;
const ID: &'static [u8] = b"secq256k1";
fn generator() -> Self::G {
Point::generator()
}
fn reduce_512(scalar: [u8; 64]) -> Self::F {
Scalar::wide_reduce(scalar)
}
fn hash_to_F(dst: &[u8], data: &[u8]) -> Self::F {
use blake2::Digest;
Scalar::wide_reduce(Self::H::digest([dst, data].concat()).as_slice().try_into().unwrap())
}
// We override the provided impl, which compares against the reserialization, because
// we already require canonicity
#[cfg(any(feature = "alloc", feature = "std"))]
#[allow(non_snake_case)]
fn read_G<R: Read>(reader: &mut R) -> io::Result<Self::G> {
use ciphersuite::group::GroupEncoding;
let mut encoding = <Self::G as GroupEncoding>::Repr::default();
reader.read_exact(encoding.as_mut())?;
let point = Option::<Self::G>::from(Self::G::from_bytes(&encoding))
.ok_or_else(|| io::Error::new(io::ErrorKind::Other, "invalid point"))?;
Ok(point)
}
}
impl generalized_bulletproofs_ec_gadgets::DiscreteLogParameters for Secq256k1 {
type ScalarBits = U<{ Scalar::NUM_BITS as usize }>;
type XCoefficients = Quot<Sum<Self::ScalarBits, U1>, U2>;
type XCoefficientsMinusOne = Diff<Self::XCoefficients, U1>;
type YxCoefficients = Diff<Quot<Sum<Sum<Self::ScalarBits, U1>, U1>, U2>, U2>;
}