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Use divn when rightshifting during rand().

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This commit is contained in:
Sean Bowe 2017-07-14 11:41:40 -06:00
parent bafb273a6c
commit d438f16628
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GPG Key ID: 95684257D8F8B031
2 changed files with 4 additions and 8 deletions
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6
src/bls12_381/fq.rs
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@ -9,7 +9,7 @@ const MODULUS_BITS: u32 = 381;
// The number of bits that must be shaved from the beginning of // The number of bits that must be shaved from the beginning of
// the representation when randomly sampling. // the representation when randomly sampling.
const REPR_SHAVE_BITS: u32 = 3; const REPR_SHAVE_BITS: usize = 3;
// R = 2**384 % q // R = 2**384 % q
const R: FqRepr = FqRepr([0x760900000002fffd, 0xebf4000bc40c0002, 0x5f48985753c758ba, 0x77ce585370525745, 0x5c071a97a256ec6d, 0x15f65ec3fa80e493]); const R: FqRepr = FqRepr([0x760900000002fffd, 0xebf4000bc40c0002, 0x5f48985753c758ba, 0x77ce585370525745, 0x5c071a97a256ec6d, 0x15f65ec3fa80e493]);
@ -368,9 +368,7 @@ impl ::rand::Rand for Fq {
fn rand<R: ::rand::Rng>(rng: &mut R) -> Self { fn rand<R: ::rand::Rng>(rng: &mut R) -> Self {
loop { loop {
let mut tmp = Fq(FqRepr::rand(rng)); let mut tmp = Fq(FqRepr::rand(rng));
for _ in 0..REPR_SHAVE_BITS { tmp.0.divn(REPR_SHAVE_BITS);
tmp.0.div2();
}
if tmp.is_valid() { if tmp.is_valid() {
return tmp return tmp
} }

6
src/bls12_381/fr.rs
View File

@ -8,7 +8,7 @@ const MODULUS_BITS: u32 = 255;
// The number of bits that must be shaved from the beginning of // The number of bits that must be shaved from the beginning of
// the representation when randomly sampling. // the representation when randomly sampling.
const REPR_SHAVE_BITS: u32 = 1; const REPR_SHAVE_BITS: usize = 1;
// R = 2**256 % r // R = 2**256 % r
const R: FrRepr = FrRepr([0x1fffffffe, 0x5884b7fa00034802, 0x998c4fefecbc4ff5, 0x1824b159acc5056f]); const R: FrRepr = FrRepr([0x1fffffffe, 0x5884b7fa00034802, 0x998c4fefecbc4ff5, 0x1824b159acc5056f]);
@ -205,9 +205,7 @@ impl ::rand::Rand for Fr {
fn rand<R: ::rand::Rng>(rng: &mut R) -> Self { fn rand<R: ::rand::Rng>(rng: &mut R) -> Self {
loop { loop {
let mut tmp = Fr(FrRepr::rand(rng)); let mut tmp = Fr(FrRepr::rand(rng));
for _ in 0..REPR_SHAVE_BITS { tmp.0.divn(REPR_SHAVE_BITS);
tmp.0.div2();
}
if tmp.is_valid() { if tmp.is_valid() {
return tmp return tmp
} }