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Add constant value of 1/2 (mod p)

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Henry de Valence 2017-01-13 13:19:08 -05:00
parent 79afc6bd0f
commit e1feb653be
1 changed files with 10 additions and 0 deletions
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10
src/constants.rs
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@ -32,6 +32,9 @@ pub const d2: FieldElement = FieldElement([
pub const SQRT_M1: FieldElement = FieldElement([ pub const SQRT_M1: FieldElement = FieldElement([
-32595792, -7943725, 9377950, 3500415, 12389472, -32595792, -7943725, 9377950, 3500415, 12389472,
-272473, -25146209, -2005654, 326686, 11406482, ]); -272473, -25146209, -2005654, 326686, 11406482, ]);
/// Precomputed value of 1/2 (mod p).
pub const HALF: FieldElement = FieldElement([
10, 0, 0, 0, 0, 0, 0, 0, 0, -16777216, ]);
/// In Montgomery form y² = x³+Ax²+x, Curve25519 has A=486662. /// In Montgomery form y² = x³+Ax²+x, Curve25519 has A=486662.
pub const A: FieldElement = FieldElement([ pub const A: FieldElement = FieldElement([
@ -1480,6 +1483,13 @@ mod test {
use curve::PreComputedPoint; use curve::PreComputedPoint;
use constants; use constants;
#[test]
fn test_half() {
let one = FieldElement([1,0,0,0,0,0,0,0,0,0]);
let two = FieldElement([2,0,0,0,0,0,0,0,0,0]);
assert_eq!(one, &two * &constants::HALF);
}
#[test] #[test]
/// Test that SQRT_M1 is a square root of -1 /// Test that SQRT_M1 is a square root of -1
fn test_sqrt_minus_one() { fn test_sqrt_minus_one() {