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Merge pull request #223 from hdevalence/ristretto-fix

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Fix variable naming in Ristretto decoding formulas
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Henry de Valence 2019-01-16 17:54:23 -08:00 committed by GitHub
commit f48980cb5b
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1 changed files with 8 additions and 8 deletions
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16
src/ristretto.rs
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@ -258,16 +258,16 @@ impl CompressedRistretto {
// Step 2. Compute (X:Y:Z:T).
let one = FieldElement::one();
let ss = s.square();
let u1 = &one + &ss; // 1 - as² where a=-1
let u2 = &one - &ss; // 1 + as²
let u1_sqr = u1.square(); // (1 + as²)²
let u1 = &one - &ss; // 1 + as²
let u2 = &one + &ss; // 1 - as² where a=-1
let u2_sqr = u2.square(); // (1 - as²)²
// v == ad(1-as²)² - (1+as²)² where d=-121665/121666
let v = &(&(-&constants::EDWARDS_D) * &u2.square()) - &u1_sqr;
// v == ad(1+as²)² - (1-as²)² where d=-121665/121666
let v = &(&(-&constants::EDWARDS_D) * &u1.square()) - &u2_sqr;
let (ok, I) = (&v * &u1_sqr).invsqrt(); // 1/sqrt(vu1²)
let (ok, I) = (&v * &u2_sqr).invsqrt(); // 1/sqrt(v*u_2²)
let Dx = &I * &u1; // 1/sqrt(v)
let Dx = &I * &u2; // 1/sqrt(v)
let Dy = &I * &(&Dx * &v); // 1/u2
// x == | 2s/sqrt(v) | == + sqrt(4s²/(ad(1+as²)² - (1-as²)²))
@ -276,7 +276,7 @@ impl CompressedRistretto {
x.conditional_negate(x_neg);
// y == (1-as²)/(1+as²)
let y = &u2 * &Dy;
let y = &u1 * &Dy;
// t == ((1+as²) sqrt(4s²/(ad(1+as²)² - (1-as²)²)))/(1-as²)
let t = &x * &y;