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ecdsa: remove NormalizeLow trait #393

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merged 1 commit into from
Nov 17, 2021
Merged

ecdsa: remove NormalizeLow trait #393

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8 changes: 4 additions & 4 deletions Cargo.lock
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37 changes: 12 additions & 25 deletions ecdsa/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@ use elliptic_curve::{
};

#[cfg(feature = "arithmetic")]
use elliptic_curve::{group::ff::PrimeField, NonZeroScalar, ProjectiveArithmetic, Scalar};
use elliptic_curve::{ff::PrimeField, IsHigh, NonZeroScalar, ScalarArithmetic};

/// Size of a fixed sized signature for the given elliptic curve.
pub type SignatureSize<C> = <FieldSize<C> as Add>::Output;
Expand Down Expand Up @@ -184,7 +184,7 @@ where
#[cfg_attr(docsrs, doc(cfg(feature = "arithmetic")))]
impl<C> Signature<C>
where
C: PrimeCurve + ProjectiveArithmetic,
C: PrimeCurve + ScalarArithmetic,
SignatureSize<C>: ArrayLength<u8>,
{
/// Get the `r` component of this signature
Expand All @@ -208,15 +208,17 @@ where
/// [BIP 0062: Dealing with Malleability][1].
///
/// [1]: https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki
pub fn normalize_s(&self) -> Option<Self>
where
Scalar<C>: NormalizeLow,
{
self.s().normalize_low().map(|s_low| {
pub fn normalize_s(&self) -> Option<Self> {
let s = self.s();

if s.is_high().into() {
let neg_s = -s;
let mut result = self.clone();
result.bytes[C::UInt::BYTE_SIZE..].copy_from_slice(&s_low.to_repr());
result
})
result.bytes[C::UInt::BYTE_SIZE..].copy_from_slice(&neg_s.to_repr());
Some(result)
} else {
None
}
}
}

Expand Down Expand Up @@ -288,18 +290,3 @@ where
})
}
}

/// Normalize a scalar (i.e. ECDSA S) to the lower half the field, as described
/// in [BIP 0062: Dealing with Malleability][1].
///
/// [1]: https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki
pub trait NormalizeLow: Sized {
/// Normalize scalar to the lower half of the field (i.e. negate it if it's
/// larger than half the curve's order).
///
/// Returns an `Option` with a new scalar if the original wasn't already
/// low-normalized.
///
/// May be implemented to work in variable time.
fn normalize_low(&self) -> Option<Self>;
}