Jon Staab
48 lines
1.6 KiB
Rust
48 lines
1.6 KiB
Rust
// Mirrors ref/frost/src/lib/refresh.ts
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use k256::Scalar;
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use crate::shares::{combine_set, create_shares};
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use crate::types::{SecretShare, SecretSharePackage};
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use crate::vss::{create_share_coeffs, get_share_commits};
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use crate::Error;
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/// Generate refresh shares for proactive secret sharing.
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/// The polynomial has a zero constant term, so adding these shares to existing
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/// shares does not change the underlying secret.
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/// Mirrors `gen_refresh_shares` in the TS implementation.
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pub fn gen_refresh_shares(
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index: u32,
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threshold: usize,
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share_max: u32,
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secrets: &[[u8; 32]],
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) -> Result<SecretSharePackage, Error> {
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// Auxiliary coefficients (threshold - 1 of them, no constant term).
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let sub_coeffs = create_share_coeffs(secrets, threshold - 1);
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// Prepend zero as the constant term so the polynomial evaluates to 0 at x=0.
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let coeffs: Vec<Scalar> = std::iter::once(Scalar::ZERO)
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.chain(sub_coeffs.iter().cloned())
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.collect();
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let shares = create_shares(&coeffs, share_max)?;
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let vss_commits = get_share_commits(&sub_coeffs);
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Ok(SecretSharePackage {
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idx: index,
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vss_commits,
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shares,
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})
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}
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/// Apply refresh shares to a current share by summing them.
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/// Mirrors `refresh_share` in the TS implementation.
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pub fn refresh_share(
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refresh_shares: &[SecretShare],
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current_share: &SecretShare,
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) -> Result<SecretShare, Error> {
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let all: Vec<SecretShare> = std::iter::once(current_share.clone())
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.chain(refresh_shares.iter().cloned())
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.collect();
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combine_set(&all)
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}
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