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Inline bit-shifting

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therealyingtong 2020-09-16 08:56:45 +08:00
parent 7710b73bff
commit a63602df2a
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1 changed files with 2 additions and 10 deletions
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12
src/arithmetic.rs
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@ -184,15 +184,6 @@ fn multiexp_serial<C: CurveAffine>(coeffs: &[C::Scalar], bases: &[C], acc: &mut
/// Uses the double-and-add algorithm with doublings shared across points. /// Uses the double-and-add algorithm with doublings shared across points.
pub fn small_multiexp<C: CurveAffine>(coeffs: &[C::Scalar], bases: &[C]) -> C::Projective { pub fn small_multiexp<C: CurveAffine>(coeffs: &[C::Scalar], bases: &[C]) -> C::Projective {
// Gets the bit at position `i`. Bits are numbered from 0 (least significant) to 7 (most significant).
fn get_bit_at(byte: u8, i: usize) -> bool {
if i < 8 {
((byte >> i) & 1u8) != 0
} else {
false
}
}
let coeffs: Vec<[u8; 32]> = coeffs.iter().map(|a| a.to_bytes()).collect(); let coeffs: Vec<[u8; 32]> = coeffs.iter().map(|a| a.to_bytes()).collect();
let mut acc = C::Projective::zero(); let mut acc = C::Projective::zero();
@ -203,7 +194,8 @@ pub fn small_multiexp<C: CurveAffine>(coeffs: &[C::Scalar], bases: &[C]) -> C::P
acc = acc.double(); acc = acc.double();
// for each coeff // for each coeff
for coeff_idx in 0..coeffs.len() { for coeff_idx in 0..coeffs.len() {
if get_bit_at(coeffs[coeff_idx][byte_idx], bit_idx) { let byte = coeffs[coeff_idx][byte_idx];
if (byte >> bit_idx & 1) != 0 {
acc = acc + &bases[coeff_idx].to_projective(); acc = acc + &bases[coeff_idx].to_projective();
} }
} }