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use std::{
convert::{TryFrom, TryInto},
marker::PhantomData,
};
use crate::{Error, Randomizer, SigType, Signature, SpendAuth, VerificationKey};
use jubjub::Scalar;
use rand_core::{CryptoRng, RngCore};
#[derive(Copy, Clone, Debug)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[cfg_attr(feature = "serde", serde(try_from = "SerdeHelper"))]
#[cfg_attr(feature = "serde", serde(into = "SerdeHelper"))]
#[cfg_attr(feature = "serde", serde(bound = "T: SigType"))]
pub struct SigningKey<T: SigType> {
sk: Scalar,
pk: VerificationKey<T>,
}
impl<'a, T: SigType> From<&'a SigningKey<T>> for VerificationKey<T> {
fn from(sk: &'a SigningKey<T>) -> VerificationKey<T> {
sk.pk.clone()
}
}
impl<T: SigType> From<SigningKey<T>> for [u8; 32] {
fn from(sk: SigningKey<T>) -> [u8; 32] {
sk.sk.to_bytes()
}
}
impl<T: SigType> TryFrom<[u8; 32]> for SigningKey<T> {
type Error = Error;
fn try_from(bytes: [u8; 32]) -> Result<Self, Self::Error> {
let maybe_sk = Scalar::from_bytes(&bytes);
if maybe_sk.is_some().into() {
let sk = maybe_sk.unwrap();
let pk = VerificationKey::from(&sk);
Ok(SigningKey { sk, pk })
} else {
Err(Error::MalformedSigningKey)
}
}
}
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
struct SerdeHelper([u8; 32]);
impl<T: SigType> TryFrom<SerdeHelper> for SigningKey<T> {
type Error = Error;
fn try_from(helper: SerdeHelper) -> Result<Self, Self::Error> {
helper.0.try_into()
}
}
impl<T: SigType> From<SigningKey<T>> for SerdeHelper {
fn from(sk: SigningKey<T>) -> Self {
Self(sk.into())
}
}
impl SigningKey<SpendAuth> {
pub fn randomize(&self, randomizer: &Randomizer) -> SigningKey<SpendAuth> {
let sk = &self.sk + randomizer;
let pk = VerificationKey::from(&sk);
SigningKey { sk, pk }
}
}
impl<T: SigType> SigningKey<T> {
pub fn new<R: RngCore + CryptoRng>(mut rng: R) -> SigningKey<T> {
let sk = {
let mut bytes = [0; 64];
rng.fill_bytes(&mut bytes);
Scalar::from_bytes_wide(&bytes)
};
let pk = VerificationKey::from(&sk);
SigningKey { sk, pk }
}
pub fn sign<R: RngCore + CryptoRng>(&self, mut rng: R, msg: &[u8]) -> Signature<T> {
use crate::HStar;
let random_bytes = {
let mut bytes = [0; 80];
rng.fill_bytes(&mut bytes);
bytes
};
let nonce = HStar::default()
.update(&random_bytes[..])
.update(&self.pk.bytes.bytes[..])
.update(msg)
.finalize();
let r_bytes = jubjub::AffinePoint::from(&T::basepoint() * &nonce).to_bytes();
let c = HStar::default()
.update(&r_bytes[..])
.update(&self.pk.bytes.bytes[..])
.update(msg)
.finalize();
let s_bytes = (&nonce + &(&c * &self.sk)).to_bytes();
Signature {
r_bytes,
s_bytes,
_marker: PhantomData,
}
}
}