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use blake2::Blake2b;
use bls12_381_plus::Scalar;
use ff::Field;
use hkdf::HkdfExtract;
use rand_chacha::ChaChaRng;
use rand_core::{CryptoRng, RngCore, SeedableRng};
use serde::{Deserialize, Serialize};
use signature_core::lib::*;
use zeroize::Zeroize;
#[derive(Clone, Debug, Eq, PartialEq, Deserialize, Serialize)]
pub struct SecretKey {
pub(crate) w: Scalar,
pub(crate) x: Scalar,
#[serde(with = "VecSerializer")]
pub(crate) y: Vec<Scalar, 128>,
}
impl Zeroize for SecretKey {
fn zeroize(&mut self) {
self.w.zeroize();
self.x.zeroize();
for y in self.y.iter_mut() {
y.zeroize();
}
}
}
impl Drop for SecretKey {
fn drop(&mut self) {
self.zeroize();
}
}
impl Default for SecretKey {
fn default() -> Self {
Self {
w: Scalar::zero(),
x: Scalar::zero(),
y: Vec::new(),
}
}
}
impl SecretKey {
const SCALAR_SIZE: usize = 32;
pub fn hash<B: AsRef<[u8]>>(count: usize, data: B) -> Option<Self> {
const SALT: &[u8] = b"PS-SIG-KEYGEN-SALT-";
let info = (count as u32).to_be_bytes();
let mut extractor = HkdfExtract::<Blake2b>::new(Some(SALT));
extractor.input_ikm(data.as_ref());
extractor.input_ikm(&[0u8]);
let mut okm = [0u8; 32];
let (_, h) = extractor.finalize();
let _ = h.expand(&info[..], &mut okm);
let rng = ChaChaRng::from_seed(okm);
generate_secret_key(count, rng)
}
pub fn random(count: usize, rng: impl RngCore + CryptoRng) -> Option<Self> {
generate_secret_key(count, rng)
}
pub fn to_bytes(&self, buffer: &mut [u8]) {
fn to_be_bytes(s: Scalar) -> [u8; 32] {
let mut t = s.to_bytes();
t.reverse();
t
}
let mut offset = 0;
let mut end = Self::SCALAR_SIZE;
buffer[offset..end].copy_from_slice(&to_be_bytes(self.w)[..]);
offset = end;
end += Self::SCALAR_SIZE;
buffer[offset..end].copy_from_slice(&to_be_bytes(self.x)[..]);
offset = end;
end += Self::SCALAR_SIZE;
for y in &self.y {
buffer[offset..end].copy_from_slice(&to_be_bytes(*y)[..]);
offset = end;
end += Self::SCALAR_SIZE;
}
}
pub fn from_bytes<B: AsRef<[u8]>>(bytes: B) -> Option<Self> {
const MIN_SIZE: usize = SecretKey::SCALAR_SIZE * 3;
let buffer = bytes.as_ref();
if buffer.len() % Self::SCALAR_SIZE != 0 {
return None;
}
if buffer.len() < MIN_SIZE {
return None;
}
fn from_be_bytes(d: &[u8]) -> Scalar {
let mut t = <[u8; SecretKey::SCALAR_SIZE]>::try_from(d).expect("invalid length");
t.reverse();
Scalar::from_bytes(&t).unwrap()
}
let y_cnt = (buffer.len() / Self::SCALAR_SIZE) - 2;
let mut offset = 0;
let mut end = Self::SCALAR_SIZE;
let w = from_be_bytes(&buffer[offset..end]);
offset = end;
end += Self::SCALAR_SIZE;
let x = from_be_bytes(&buffer[offset..end]);
offset = end;
end += Self::SCALAR_SIZE;
let mut y = Vec::new();
for _ in 0..y_cnt {
if y.push(from_be_bytes(&buffer[offset..end])).is_err() {
return None;
}
}
Some(Self { w, x, y })
}
pub fn is_valid(&self) -> bool {
let mut res = !self.w.is_zero();
res &= !self.x.is_zero();
for y in &self.y {
res &= !y.is_zero();
}
res
}
pub fn is_invalid(&self) -> bool {
let mut res = self.w.is_zero();
res |= self.x.is_zero();
for y in &self.y {
res |= y.is_zero();
}
res
}
}
fn generate_secret_key(count: usize, mut rng: impl RngCore + CryptoRng) -> Option<SecretKey> {
if count == 0 || count > 128 {
return None;
}
let w = Scalar::random(&mut rng);
let x = Scalar::random(&mut rng);
let mut y = Vec::new();
for _ in 0..count {
if y.push(Scalar::random(&mut rng)).is_err() {
return None;
}
}
Some(SecretKey { w, x, y })
}