mirror of https://github.com/zcash/orchard.git
Use mixed addition for Sinsemilla bases
Performance improvements: - MerkleCRH: ~5% - Commit^ivk: ~1% - NoteCommit: ~3%
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@ -1,6 +1,6 @@
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//! The Sinsemilla hash function and commitment scheme.
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use group::{prime::PrimeCurveAffine, Wnaf};
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use group::Wnaf;
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use halo2::arithmetic::{CurveAffine, CurveExt};
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use pasta_curves::pallas;
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use subtle::CtOption;
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@ -120,7 +120,7 @@ impl HashDomain {
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.chunks(K)
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.fold(IncompletePoint::from(self.Q), |acc, chunk| {
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let (S_x, S_y) = SINSEMILLA_S[lebs2ip_k(chunk) as usize];
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let S_chunk = pallas::Affine::from_xy(S_x, S_y).unwrap().to_curve();
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let S_chunk = pallas::Affine::from_xy(S_x, S_y).unwrap();
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(acc + S_chunk) + acc
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})
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}
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@ -1,6 +1,6 @@
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use std::ops::Add;
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use group::Group;
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use group::{cofactor::CofactorCurveAffine, Group};
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use pasta_curves::pallas;
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use subtle::{ConstantTimeEq, CtOption};
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@ -53,3 +53,28 @@ impl Add<pallas::Point> for IncompletePoint {
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self + IncompletePoint(CtOption::new(rhs, 1.into()))
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}
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}
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impl Add<pallas::Affine> for IncompletePoint {
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type Output = IncompletePoint;
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/// Specialisation of incomplete addition for mixed addition.
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fn add(self, rhs: pallas::Affine) -> Self::Output {
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// ⊥ ⊹ ⊥ = ⊥
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// ⊥ ⊹ P = ⊥
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IncompletePoint(self.0.and_then(|p| {
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// P ⊹ ⊥ = ⊥ is satisfied by definition.
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let q = rhs.to_curve();
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// 0 ⊹ 0 = ⊥
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// 0 ⊹ P = ⊥
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// P ⊹ 0 = ⊥
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// (x, y) ⊹ (x', y') = ⊥ if x == x'
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// (x, y) ⊹ (x', y') = (x, y) + (x', y') if x != x'
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CtOption::new(
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// Use mixed addition for efficiency.
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p + rhs,
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!(p.is_identity() | q.is_identity() | p.ct_eq(&q) | p.ct_eq(&-q)),
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)
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}))
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}
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}
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