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Add constant for MSQRT_M1, equal to -SQRT_M1

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This commit is contained in:
Henry de Valence 2017-02-19 18:09:02 -05:00
parent e1feb653be
commit fb0c431184
1 changed files with 13 additions and 2 deletions
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15
src/constants.rs
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@ -29,9 +29,18 @@ pub const d: FieldElement = FieldElement([
pub const d2: FieldElement = FieldElement([ pub const d2: FieldElement = FieldElement([
-21827239, -5839606, -30745221, 13898782, 229458, -21827239, -5839606, -30745221, 13898782, 229458,
15978800, -12551817, -6495438, 29715968, 9444199, ]); 15978800, -12551817, -6495438, 29715968, 9444199, ]);
/// Precomputed value of one of the square roots of -1 (mod p)
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 the other square root of -1 (mod p),
/// i.e., MSQRT_M1 = -SQRT_M1.
pub const MSQRT_M1: FieldElement = FieldElement([
32595792, 7943725, -9377950, -3500415, -12389472,
272473, 25146209, 2005654, -326686, -11406482, ]);
/// Precomputed value of 1/2 (mod p). /// Precomputed value of 1/2 (mod p).
pub const HALF: FieldElement = FieldElement([ pub const HALF: FieldElement = FieldElement([
10, 0, 0, 0, 0, 0, 0, 0, 0, -16777216, ]); 10, 0, 0, 0, 0, 0, 0, 0, 0, -16777216, ]);
@ -1491,11 +1500,13 @@ mod test {
} }
#[test] #[test]
/// Test that SQRT_M1 is a square root of -1 /// Test that SQRT_M1 and MSQRT_M1 are square roots of -1
fn test_sqrt_minus_one() { fn test_sqrt_minus_one() {
let minus_one = FieldElement([-1,0,0,0,0,0,0,0,0,0]); let minus_one = FieldElement([-1,0,0,0,0,0,0,0,0,0]);
let sqrt_m1_sq = &constants::SQRT_M1 * &constants::SQRT_M1; let sqrt_m1_sq = &constants::SQRT_M1 * &constants::SQRT_M1;
assert_eq!(minus_one, sqrt_m1_sq); let msqrt_m1_sq = &constants::MSQRT_M1 * &constants::MSQRT_M1;
assert_eq!(minus_one, sqrt_m1_sq);
assert_eq!(minus_one, msqrt_m1_sq);
} }
#[test] #[test]