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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`.
63 lines
1.5 KiB
Rust
63 lines
1.5 KiB
Rust
use prime_field::subtle::CtOption;
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use sha3::{
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digest::{
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typenum::U114, core_api::BlockSizeUser, Update, Output, OutputSizeUser, FixedOutput,
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ExtendableOutput, XofReader, HashMarker,
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},
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Shake256,
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};
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use ciphersuite::{group::GroupEncoding, Id, WithPreferredHash, GroupCanonicalEncoding};
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use crate::Point;
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/// Shake256, fixed to a 114-byte output, as used by Ed448.
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#[derive(Clone, Default)]
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pub struct Shake256_114(Shake256);
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impl BlockSizeUser for Shake256_114 {
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type BlockSize = <Shake256 as BlockSizeUser>::BlockSize;
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fn block_size() -> usize {
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Shake256::block_size()
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}
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}
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impl OutputSizeUser for Shake256_114 {
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type OutputSize = U114;
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fn output_size() -> usize {
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114
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}
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}
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impl Update for Shake256_114 {
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fn update(&mut self, data: &[u8]) {
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self.0.update(data);
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}
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fn chain(mut self, data: impl AsRef<[u8]>) -> Self {
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Update::update(&mut self, data.as_ref());
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self
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}
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}
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impl FixedOutput for Shake256_114 {
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fn finalize_fixed(self) -> Output<Self> {
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let mut res = Default::default();
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FixedOutput::finalize_into(self, &mut res);
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res
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}
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fn finalize_into(self, out: &mut Output<Self>) {
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let mut reader = self.0.finalize_xof();
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reader.read(out);
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}
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}
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impl HashMarker for Shake256_114 {}
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impl Id for Point {
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const ID: &[u8] = b"ed448";
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}
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impl WithPreferredHash for Point {
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type H = Shake256_114;
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}
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impl GroupCanonicalEncoding for Point {
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fn from_canonical_bytes(bytes: &<Self::G as GroupEncoding>::Repr) -> CtOption<Self::G> {
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Self::G::from_bytes(bytes)
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}
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}
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