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Group trait overhaul part 2 (#53)

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* Rely on elliptic-curve for hash-to-curve and P-256 implementations

* Update MSRV

* Remove unnecessary `#[macro_use]`

* Re-introduce `CipherSuite`

* Provide types for length shortcuts

* Remove `SUITE_ID` from `Group`

* Blanket implementation for RustCrypto `Curve`s

* Remove the p256 crate feature

* Rename `ristretto_*` crate features to `ristretto-*` for consistency

* Remove unnecessary allowed Clippy lints

* Remove some unnecessary constraints
This commit is contained in:
daxpedda
2022-01-21 13:52:09 -08:00
committed by GitHub
parent 652fd1d1d0
commit 16e072dcd4
15 changed files with 1038 additions and 1643 deletions
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src/group/ristretto.rs
+33 -24
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@@ -5,31 +5,37 @@
// License, Version 2.0 found in the LICENSE-APACHE file in the root directory
// of this source tree.
use core::convert::TryInto;
use curve25519_dalek::constants::RISTRETTO_BASEPOINT_POINT;
use curve25519_dalek::ristretto::{CompressedRistretto, RistrettoPoint};
use curve25519_dalek::scalar::Scalar;
use curve25519_dalek::traits::Identity;
use digest::core_api::BlockSizeUser;
use digest::{Digest, FixedOutputReset};
use digest::OutputSizeUser;
use elliptic_curve::hash2curve::{ExpandMsg, ExpandMsgXmd, Expander};
use generic_array::sequence::Concat;
use generic_array::typenum::{U32, U64};
use generic_array::typenum::{IsLess, IsLessOrEqual, U256, U32, U64};
use generic_array::GenericArray;
use rand_core::{CryptoRng, RngCore};
use super::{expand, Group, STR_HASH_TO_GROUP, STR_HASH_TO_SCALAR};
use super::{Group, STR_HASH_TO_GROUP, STR_HASH_TO_SCALAR};
use crate::voprf::{self, Mode};
use crate::{Error, Result};
use crate::{CipherSuite, Error, Result};
/// [`Group`] implementation for Ristretto255.
pub struct Ristretto255;
#[cfg(feature = "ristretto255-ciphersuite")]
impl crate::CipherSuite for Ristretto255 {
const ID: u16 = 0x0001;
type Group = Ristretto255;
type Hash = sha2::Sha512;
}
// `cfg` here is only needed because of a bug in Rust's crate feature documentation. See: https://github.com/rust-lang/rust/issues/83428
#[cfg(feature = "ristretto255")]
impl Group for Ristretto255 {
const SUITE_ID: u16 = 0x0001;
type Elem = RistrettoPoint;
type ElemLen = U32;
@@ -40,35 +46,38 @@ impl Group for Ristretto255 {
// Implements the `hash_to_ristretto255()` function from
// https://www.ietf.org/archive/id/draft-irtf-cfrg-hash-to-curve-10.txt
fn hash_to_curve<H: BlockSizeUser + Digest + FixedOutputReset>(
msg: &[&[u8]],
mode: Mode,
) -> Result<Self::Elem> {
fn hash_to_curve<CS: CipherSuite>(msg: &[&[u8]], mode: Mode) -> Result<Self::Elem>
where
<CS::Hash as OutputSizeUser>::OutputSize:
IsLess<U256> + IsLessOrEqual<<CS::Hash as BlockSizeUser>::BlockSize>,
{
let dst =
GenericArray::from(STR_HASH_TO_GROUP).concat(voprf::get_context_string::<Self>(mode));
let uniform_bytes = expand::expand_message_xmd::<H, U64>(msg, &dst)?;
let mut uniform_bytes = GenericArray::<_, U64>::default();
ExpandMsgXmd::<CS::Hash>::expand_message(msg, &dst, 64)
.map_err(|_| Error::PointError)?
.fill_bytes(&mut uniform_bytes);
Ok(RistrettoPoint::from_uniform_bytes(&uniform_bytes.into()))
}
// Implements the `HashToScalar()` function from
// https://www.ietf.org/archive/id/draft-irtf-cfrg-voprf-07.html#section-4.1
fn hash_to_scalar<'a, H: BlockSizeUser + Digest + FixedOutputReset>(
input: &[&[u8]],
mode: Mode,
) -> Result<Self::Scalar> {
fn hash_to_scalar<'a, CS: CipherSuite>(input: &[&[u8]], mode: Mode) -> Result<Self::Scalar>
where
<CS::Hash as OutputSizeUser>::OutputSize:
IsLess<U256> + IsLessOrEqual<<CS::Hash as BlockSizeUser>::BlockSize>,
{
let dst =
GenericArray::from(STR_HASH_TO_SCALAR).concat(voprf::get_context_string::<Self>(mode));
let uniform_bytes = expand::expand_message_xmd::<H, U64>(input, &dst)?;
let mut uniform_bytes = GenericArray::<_, U64>::default();
ExpandMsgXmd::<CS::Hash>::expand_message(input, &dst, 64)
.map_err(|_| Error::PointError)?
.fill_bytes(&mut uniform_bytes);
Ok(Scalar::from_bytes_mod_order_wide(
uniform_bytes
.as_slice()
.try_into()
.map_err(|_| Error::HashToCurveError)?,
))
Ok(Scalar::from_bytes_mod_order_wide(&uniform_bytes.into()))
}
fn base_elem() -> Self::Elem {