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Added constants to reduce recalculations in elligator_risteretto_flavor

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This commit is contained in:
Trangar 2019-10-28 11:48:33 +01:00
parent 82ea371b19
commit ae4bf40e28
3 changed files with 48 additions and 4 deletions
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15
src/backend/serial/u32/constants.rs
View file

@ -18,6 +18,11 @@ use backend::serial::u32::scalar::Scalar29;
use edwards::{EdwardsBasepointTable, EdwardsPoint};
use window::{LookupTable, NafLookupTable8};
/// The value of minus one, equal to `-&FieldElement::one()`
pub(crate) const MINUS_ONE: FieldElement2625 = FieldElement2625([
67108844, 33554431, 67108863, 33554431, 67108863, 33554431, 67108863, 33554431, 67108863, 33554431
]);
/// Edwards `d` value, equal to `-121665/121666 mod p`.
pub(crate) const EDWARDS_D: FieldElement2625 = FieldElement2625([
56195235, 13857412, 51736253, 6949390, 114729, 24766616, 60832955, 30306712, 48412415, 21499315,
@ -28,6 +33,16 @@ pub(crate) const EDWARDS_D2: FieldElement2625 = FieldElement2625([
45281625, 27714825, 36363642, 13898781, 229458, 15978800, 54557047, 27058993, 29715967, 9444199,
]);
/// One minus edwards `d` value squared, equal to `(1 - (-121665/121666) mod p) pow 2`
pub(crate) const ONE_MINUS_EDWARDS_D_SQUARED: FieldElement2625 = FieldElement2625([
6275446, 16937061, 44170319, 29780721, 11667076, 7397348, 39186143, 1766194, 42675006, 672202
]);
/// Edwards `d` value minus one squared, equal to `(((-121665/121666) mod p) - 1) pow 2`
pub(crate) const EDWARDS_D_MINUS_ONE_SQUARED: FieldElement2625 = FieldElement2625([
15551776, 22456977, 53683765, 23429360, 55212328, 10178283, 40474537, 4729243, 61826754, 23438029
]);
/// `= sqrt(a*d - 1)`, where `a = -1 (mod p)`, `d` are the Edwards curve parameters.
pub(crate) const SQRT_AD_MINUS_ONE: FieldElement2625 = FieldElement2625([
24849947, 33400850, 43495378, 6347714, 46036536, 32887293, 41837720, 18186727, 66238516,

27
src/backend/serial/u64/constants.rs
View file

@ -16,6 +16,15 @@ use backend::serial::u64::scalar::Scalar52;
use edwards::{EdwardsBasepointTable, EdwardsPoint};
use window::{LookupTable, NafLookupTable8};
/// The value of minus one, equal to `-&FieldElement::one()`
pub(crate) const MINUS_ONE: FieldElement51 = FieldElement51([
2251799813685228,
2251799813685247,
2251799813685247,
2251799813685247,
2251799813685247
]);
/// Edwards `d` value, equal to `-121665/121666 mod p`.
pub(crate) const EDWARDS_D: FieldElement51 = FieldElement51([
929955233495203,
@ -34,6 +43,24 @@ pub(crate) const EDWARDS_D2: FieldElement51 = FieldElement51([
633789495995903,
]);
/// One minus edwards `d` value squared, equal to `(1 - (-121665/121666) mod p) pow 2`
pub(crate) const ONE_MINUS_EDWARDS_D_SQUARED: FieldElement51 = FieldElement51([
1136626929484150,
1998550399581263,
496427632559748,
118527312129759,
45110755273534
]);
/// Edwards `d` value minus one squared, equal to `(((-121665/121666) mod p) - 1) pow 2`
pub(crate) const EDWARDS_D_MINUS_ONE_SQUARED: FieldElement51 = FieldElement51([
1507062230895904,
1572317787530805,
683053064812840,
317374165784489,
1572899562415810
]);
/// `= sqrt(a*d - 1)`, where `a = -1 (mod p)`, `d` are the Edwards curve parameters.
pub(crate) const SQRT_AD_MINUS_ONE: FieldElement51 = FieldElement51([
2241493124984347,

10
src/ristretto.rs
View file

@ -598,14 +598,16 @@ impl RistrettoPoint {
/// This method is not public because it's just used for hashing
/// to a point -- proper elligator support is deferred for now.
pub(crate) fn elligator_ristretto_flavor(r_0: &FieldElement) -> RistrettoPoint {
let (i, d) = (&constants::SQRT_M1, &constants::EDWARDS_D);
let i = &constants::SQRT_M1;
let d = &constants::EDWARDS_D;
let one_minus_d_sq = &constants::ONE_MINUS_EDWARDS_D_SQUARED;
let d_minus_one_sq = &constants::EDWARDS_D_MINUS_ONE_SQUARED;
let mut c = constants::MINUS_ONE;
let one = FieldElement::one();
let one_minus_d_sq = &one - &d.square();
let d_minus_one_sq = (d - &one).square();
let r = i * &r_0.square();
let N_s = &(&r + &one) * &one_minus_d_sq;
let mut c = -&one;
let D = &(&c - &(d * &r)) * &(&r + d);
let (Ns_D_is_sq, mut s) = FieldElement::sqrt_ratio_i(&N_s, &D);