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Connect double_scalar_mult_basepoint to AVX2 backend

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Henry de Valence 2017-12-04 11:05:24 -08:00
parent 2c29d9a2ad
commit 7d2d87441b
1 changed files with 46 additions and 35 deletions
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81
src/edwards.rs
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@ -849,49 +849,60 @@ pub mod vartime {
/// \\(aA+bB\\), where \\(B\\) is the Ed25519 basepoint (i.e., \\(B = (x,4/5)\\)
/// with x positive).
#[cfg(feature="precomputed_tables")]
pub fn double_scalar_mult_basepoint(a: &Scalar,
A: &ExtendedPoint,
b: &Scalar) -> ExtendedPoint {
let a_naf = a.non_adjacent_form();
let b_naf = b.non_adjacent_form();
pub fn double_scalar_mult_basepoint(
a: &Scalar,
A: &ExtendedPoint,
b: &Scalar,
) -> ExtendedPoint {
// If we built with AVX2, use the AVX2 backend.
#[cfg(all(target_feature = "avx2", feature = "avx2_backend"))] {
use backend::avx2::edwards as edwards_avx2;
// Find starting index
let mut i: usize = 255;
for j in (0..255).rev() {
i = j;
if a_naf[i] != 0 || b_naf[i] != 0 {
break;
}
edwards_avx2::vartime::double_scalar_mult_basepoint(a, A, b)
}
// Otherwise, proceed as normal:
#[cfg(not(all(target_feature = "avx2", feature = "avx2_backend")))] {
let a_naf = a.non_adjacent_form();
let b_naf = b.non_adjacent_form();
let odd_multiples_of_A = OddMultiples::create(A);
let odd_multiples_of_B = &constants::AFFINE_ODD_MULTIPLES_OF_BASEPOINT;
let mut r = ProjectivePoint::identity();
loop {
let mut t = r.double();
if a_naf[i] > 0 {
t = &t.to_extended() + &odd_multiples_of_A[( a_naf[i]/2) as usize];
} else if a_naf[i] < 0 {
t = &t.to_extended() - &odd_multiples_of_A[(-a_naf[i]/2) as usize];
// Find starting index
let mut i: usize = 255;
for j in (0..255).rev() {
i = j;
if a_naf[i] != 0 || b_naf[i] != 0 {
break;
}
}
if b_naf[i] > 0 {
t = &t.to_extended() + &odd_multiples_of_B[( b_naf[i]/2) as usize];
} else if b_naf[i] < 0 {
t = &t.to_extended() - &odd_multiples_of_B[(-b_naf[i]/2) as usize];
let odd_multiples_of_A = OddMultiples::create(A);
let odd_multiples_of_B = &constants::AFFINE_ODD_MULTIPLES_OF_BASEPOINT;
let mut r = ProjectivePoint::identity();
loop {
let mut t = r.double();
if a_naf[i] > 0 {
t = &t.to_extended() + &odd_multiples_of_A[( a_naf[i]/2) as usize];
} else if a_naf[i] < 0 {
t = &t.to_extended() - &odd_multiples_of_A[(-a_naf[i]/2) as usize];
}
if b_naf[i] > 0 {
t = &t.to_extended() + &odd_multiples_of_B[( b_naf[i]/2) as usize];
} else if b_naf[i] < 0 {
t = &t.to_extended() - &odd_multiples_of_B[(-b_naf[i]/2) as usize];
}
r = t.to_projective();
if i == 0 {
break;
}
i -= 1;
}
r = t.to_projective();
if i == 0 {
break;
}
i -= 1;
r.to_extended()
}
r.to_extended()
}
}