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a141deaf36
This helps identify where the various functionalities are used, or rather, not used. The `Ciphersuite` trait present in `patches/ciphersuite`, facilitating the entire FCMP++ tree, only requires the markers _and_ canonical point decoding. I've opened a PR to upstream such a trait into `group` (https://github.com/zkcrypto/group/pull/68). `WrappedGroup` is still justified for as long as `Group::generator` exists. Moving `::generator()` to its own trait, on an independent structure (upstream) would be massively appreciated. @tarcieri also wanted to update from `fn generator()` to `const GENERATOR`, which would encourage further discussion on https://github.com/zkcrypto/group/issues/32 and https://github.com/zkcrypto/group/issues/45, which have been stagnant. The `Id` trait is occasionally used yet really should be first off the chopping block. Finally, `WithPreferredHash` is only actually used around a third of the time, which more than justifies it being a separate trait. --- Updates `dalek_ff_group::Scalar` to directly re-export `curve25519_dalek::Scalar`, as without issue. `dalek_ff_group::RistrettoPoint` also could be replaced with an export of `curve25519_dalek::RistrettoPoint`, yet the coordinator relies on how we implemented `Hash` on it for the hell of it so it isn't worth it at this time. `dalek_ff_group::EdwardsPoint` can't be replaced for an re-export of `curve25519_dalek::SubgroupPoint` as it doesn't implement `zeroize`, `subtle` traits within a released, non-yanked version. Relevance to https://github.com/serai-dex/serai/issues/201 and https://github.com/dalek-cryptography/curve25519-dalek/issues/811#issuecomment-3247732746. Also updates the `Ristretto` ciphersuite to prefer `Blake2b-512` over `SHA2-512`. In order to maintain compliance with FROST's IETF standard, `modular-frost` defines its own ciphersuite for Ristretto which still uses `SHA2-512`.
69 lines
2.2 KiB
Rust
69 lines
2.2 KiB
Rust
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
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#![doc = include_str!("../README.md")]
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#![no_std]
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use core::ops::Deref;
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use std_shims::{vec::Vec, collections::HashMap};
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use zeroize::{Zeroize, Zeroizing};
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use rand_core::{RngCore, CryptoRng};
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use ciphersuite::{
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group::ff::{Field, PrimeField},
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GroupIo, Id,
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};
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pub use dkg::*;
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/// Create a key via a dealer key generation protocol.
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pub fn key_gen<R: RngCore + CryptoRng, C: GroupIo + Id>(
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rng: &mut R,
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threshold: u16,
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participants: u16,
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) -> Result<HashMap<Participant, ThresholdKeys<C>>, DkgError> {
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let mut coefficients = Vec::with_capacity(usize::from(participants));
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// `.max(1)` so we always generate the 0th coefficient which we'll share
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for _ in 0 .. threshold.max(1) {
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coefficients.push(Zeroizing::new(C::F::random(&mut *rng)));
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}
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fn polynomial<F: PrimeField + Zeroize>(
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coefficients: &[Zeroizing<F>],
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l: Participant,
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) -> Zeroizing<F> {
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let l = F::from(u64::from(u16::from(l)));
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// This should never be reached since Participant is explicitly non-zero
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assert!(l != F::ZERO, "zero participant passed to polynomial");
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let mut share = Zeroizing::new(F::ZERO);
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for (idx, coefficient) in coefficients.iter().rev().enumerate() {
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*share += coefficient.deref();
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if idx != (coefficients.len() - 1) {
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*share *= l;
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}
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}
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share
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}
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let group_key = C::generator() * coefficients[0].deref();
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let mut secret_shares = HashMap::with_capacity(participants as usize);
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let mut verification_shares = HashMap::with_capacity(participants as usize);
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for i in 1 ..= participants {
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let i = Participant::new(i).expect("non-zero u16 wasn't a valid Participant index");
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let secret_share = polynomial(&coefficients, i);
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secret_shares.insert(i, secret_share.clone());
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verification_shares.insert(i, C::generator() * *secret_share);
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}
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let mut res = HashMap::with_capacity(participants as usize);
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for (i, secret_share) in secret_shares {
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let keys = ThresholdKeys::new(
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ThresholdParams::new(threshold, participants, i)?,
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Interpolation::Lagrange,
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secret_share,
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verification_shares.clone(),
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)?;
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debug_assert_eq!(keys.group_key(), group_key);
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res.insert(i, keys);
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}
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Ok(res)
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}
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