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Correct verification share calculation from n * n * t to just n * t

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Reduces key gen execution time by a factor of 3.
This commit is contained in:
Luke Parker 2022-05-29 19:52:27 -04:00
parent f6a41d9836
commit 5a1f273cd5
No known key found for this signature in database
GPG key ID: F9F1386DB1E119B6
1 changed files with 11 additions and 13 deletions
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24
crypto/frost/src/key_gen.rs
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@ -1,4 +1,4 @@
use core::{convert::TryFrom, fmt};
use core::fmt;
use std::collections::HashMap;
use rand_core::{RngCore, CryptoRng};
@ -230,19 +230,17 @@ fn complete_r2<R: RngCore + CryptoRng, C: Curve>(
}
let mut verification_shares = HashMap::new();
for l in 1 ..= params.n() {
let mut values = vec![];
for i in 1 ..= params.n() {
for j in 0 .. params.t() {
let mut exp = C::F::one();
for _ in 0 .. j {
exp *= C::F::from(u64::try_from(l).unwrap());
}
values.push((exp, commitments[&i][usize::from(j)]));
}
}
// Doesn't do a unified multiexp due to needing individual verification shares
verification_shares.insert(l, multiexp_vartime(values, C::little_endian()));
let i_scalar = C::F::from(i.into());
let mut values = vec![];
(0 .. params.t()).into_iter().fold(C::F::one(), |exp, j| {
values.push((
exp,
(1 ..= params.n()).into_iter().map(|l| commitments[&l][usize::from(j)]).sum()
));
exp * i_scalar
});
verification_shares.insert(i, multiexp_vartime(values, C::little_endian()));
}
debug_assert_eq!(C::generator_table() * secret_share, verification_shares[&params.i()]);