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feat: impl recoverable RandomizedPrehashSigner for SigningKey #878

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Merged
tarcieri merged 1 commit into from
Jan 19, 2025
Merged

feat: impl recoverable RandomizedPrehashSigner for SigningKey #878

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55 changes: 53 additions & 2 deletions ecdsa/src/recovery.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,13 @@ use crate::{Error, Result};
#[cfg(feature = "signing")]
use {
crate::{hazmat::sign_prehashed_rfc6979, SigningKey},
elliptic_curve::subtle::CtOption,
signature::{hazmat::PrehashSigner, DigestSigner, Signer},
elliptic_curve::{subtle::CtOption, FieldBytes},
signature::{
digest::FixedOutput,
hazmat::{PrehashSigner, RandomizedPrehashSigner},
rand_core::CryptoRngCore,
DigestSigner, RandomizedDigestSigner, Signer,
},
};

#[cfg(feature = "verifying")]
Expand Down Expand Up @@ -178,6 +183,19 @@ where
Scalar<C>: Invert<Output = CtOption<Scalar<C>>>,
SignatureSize<C>: ArraySize,
{
/// Sign the given message prehash, using the given rng for the RFC6979 Section 3.6 "additional
/// data", returning a signature and recovery ID.
pub fn sign_prehash_recoverable_with_rng(
&self,
rng: &mut impl CryptoRngCore,
prehash: &[u8],
) -> Result<(Signature<C>, RecoveryId)> {
let z = bits2field::<C>(prehash)?;
let mut ad = FieldBytes::<C>::default();
rng.fill_bytes(&mut ad);
sign_prehashed_rfc6979::<C, C::Digest>(self.as_nonzero_scalar(), &z, &ad)
}

/// Sign the given message prehash, returning a signature and recovery ID.
pub fn sign_prehash_recoverable(&self, prehash: &[u8]) -> Result<(Signature<C>, RecoveryId)> {
let z = bits2field::<C>(prehash)?;
Expand Down Expand Up @@ -212,6 +230,39 @@ where
}
}

#[cfg(feature = "signing")]
impl<C> RandomizedPrehashSigner<(Signature<C>, RecoveryId)> for SigningKey<C>
where
C: EcdsaCurve + CurveArithmetic + DigestPrimitive,
Scalar<C>: Invert<Output = CtOption<Scalar<C>>>,
SignatureSize<C>: ArraySize,
{
fn sign_prehash_with_rng(
&self,
rng: &mut impl CryptoRngCore,
prehash: &[u8],
) -> Result<(Signature<C>, RecoveryId)> {
self.sign_prehash_recoverable_with_rng(rng, prehash)
}
}

#[cfg(feature = "signing")]
impl<C, D> RandomizedDigestSigner<D, (Signature<C>, RecoveryId)> for SigningKey<C>
where
C: EcdsaCurve + CurveArithmetic + DigestPrimitive,
D: Digest + FixedOutput,
Scalar<C>: Invert<Output = CtOption<Scalar<C>>>,
SignatureSize<C>: ArraySize,
{
fn try_sign_digest_with_rng(
&self,
rng: &mut impl CryptoRngCore,
msg_digest: D,
) -> Result<(Signature<C>, RecoveryId)> {
self.sign_prehash_with_rng(rng, &msg_digest.finalize_fixed())
}
}

#[cfg(feature = "signing")]
impl<C> PrehashSigner<(Signature<C>, RecoveryId)> for SigningKey<C>
where
Expand Down