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Move double-base scmul to the EdwardsPoint type

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This commit is contained in:
Henry de Valence 2018-05-15 11:15:53 -07:00
parent 149c5004e8
commit 2eed24109e
2 changed files with 23 additions and 33 deletions
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2
benches/dalek_benchmarks.rs
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@ -59,7 +59,7 @@ mod edwards_benches {
let a = Scalar::from_u64(298374928).invert();
let b = Scalar::from_u64(897987897).invert();
let A = B * (b * a);
bench.iter(|| edwards::vartime::double_scalar_mul_basepoint(&a, &A, &b));
bench.iter(|| EdwardsPoint::vartime_double_scalar_mul_basepoint(&a, &A, &b));
});
}

54
src/edwards.rs
View file

@ -584,6 +584,27 @@ impl VartimeMultiscalarMul for EdwardsPoint {
}
}
impl EdwardsPoint {
/// Compute \\(aA + bB\\) in variable time, where \\(B\\) is the Ed25519 basepoint.
///
/// XXX eliminate this function when we have the precomputation API
#[cfg(feature = "stage2_build")]
pub fn vartime_double_scalar_mul_basepoint(a: &Scalar, A: &EdwardsPoint, b: &Scalar) -> EdwardsPoint {
// If we built with AVX2, use the AVX2 backend.
#[cfg(all(feature="avx2_backend", target_feature="avx2"))]
{
use backend::avx2::scalar_mul::vartime_double_base::mul;
mul(a, A, b)
}
// Otherwise, proceed as normal:
#[cfg(not(all(feature="avx2_backend", target_feature="avx2")))]
{
use scalar_mul::vartime_double_base::mul;
mul(a, A, b)
}
}
}
/// A precomputed table of multiples of a basepoint, for accelerating
/// fixed-base scalar multiplication. One table, for the Ed25519
/// basepoint, is provided in the `constants` module.
@ -783,37 +804,6 @@ impl Debug for EdwardsBasepointTable {
}
}
// ------------------------------------------------------------------------
// Variable-time functions
// ------------------------------------------------------------------------
/// Variable-time operations on curve points, useful for non-secret data.
///
/// XXX delete this whole module
pub mod vartime {
//! Variable-time operations on curve points, useful for non-secret data.
use super::*;
/// Compute \\(aA + bB\\) in variable time, where \\(B\\) is the Ed25519 basepoint.
///
/// XXX eliminate this function when we have the precomputation API
#[cfg(feature = "stage2_build")]
pub fn double_scalar_mul_basepoint(a: &Scalar, A: &EdwardsPoint, b: &Scalar) -> EdwardsPoint {
// If we built with AVX2, use the AVX2 backend.
#[cfg(all(feature="avx2_backend", target_feature="avx2"))]
{
use backend::avx2::scalar_mul::vartime_double_base::mul;
mul(a, A, b)
}
// Otherwise, proceed as normal:
#[cfg(not(all(feature="avx2_backend", target_feature="avx2")))]
{
use scalar_mul::vartime_double_base::mul;
mul(a, A, b)
}
}
}
// ------------------------------------------------------------------------
// Tests
// ------------------------------------------------------------------------
@ -1143,7 +1133,7 @@ mod test {
#[test]
fn double_scalar_mul_basepoint_vs_ed25519py() {
let A = A_TIMES_BASEPOINT.decompress().unwrap();
let result = vartime::double_scalar_mul_basepoint(&A_SCALAR, &A, &B_SCALAR);
let result = EdwardsPoint::vartime_double_scalar_mul_basepoint(&A_SCALAR, &A, &B_SCALAR);
assert_eq!(result.compress(), DOUBLE_SCALAR_MULT_RESULT);
}