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Make normalize_low() pure #119

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Merged
tarcieri merged 1 commit into from
Aug 6, 2020
Merged

Make normalize_low() pure #119

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16 changes: 10 additions & 6 deletions ecdsa/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -155,10 +155,10 @@ where

// Not constant time, but we're operating on public values
if s_option.is_some().into() {
let mut s = s_option.unwrap();
let (s_low, was_high) = s_option.unwrap().normalize_low();

if s.normalize_low() {
s_bytes.copy_from_slice(&s.into());
if was_high {
s_bytes.copy_from_slice(&s_low.into());
Ok(true)
} else {
Ok(false)
Expand Down Expand Up @@ -248,8 +248,12 @@ where
/// in [BIP 0062: Dealing with Malleability][1].
///
/// [1]: https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki
pub trait NormalizeLow {
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)
fn normalize_low(&mut self) -> bool;
/// larger than half the curve's order).
/// Returns a tuple with the new scalar and a boolean indicating whether the given scalar
/// was in the higher half.
///
/// May be implemented to work in variable time.
fn normalize_low(&self) -> (Self, bool);
}