Remove CipherSuite (#20)

* Remove `Hash`

* Remove `CipherSuite`

* Remove single field `struct`s

src/group/expand.rs

@@ -6,7 +6,6 @@
 // of this source tree.
 
 use crate::errors::InternalError;
-use crate::hash::Hash;
 use crate::serialization::i2osp;
 use alloc::vec::Vec;
 use digest::{BlockInput, Digest};
@@ -28,7 +27,7 @@ fn xor(x: &[u8], y: &[u8]) -> Result<Vec<u8>, InternalError> {
 
 /// Corresponds to the expand_message_xmd() function defined in
 /// <https://www.ietf.org/archive/id/draft-irtf-cfrg-hash-to-curve-10.txt>
-pub fn expand_message_xmd<H: Hash>(
+pub fn expand_message_xmd<H: BlockInput + Digest>(
     msg: &[u8],
     dst: &[u8],
     len_in_bytes: usize,

src/group/mod.rs

@@ -14,8 +14,8 @@ pub(crate) mod p256;
 mod ristretto;
 
 use crate::errors::InternalError;
-use crate::hash::Hash;
 use core::ops::{Add, Mul, Sub};
+use digest::{BlockInput, Digest};
 use generic_array::{ArrayLength, GenericArray};
 use rand::{CryptoRng, RngCore};
 use zeroize::Zeroize;
@@ -33,10 +33,14 @@ pub trait Group:
     const SUITE_ID: usize;
 
     /// transforms a password and domain separation tag (DST) into a curve point
-    fn hash_to_curve<H: Hash>(msg: &[u8], dst: &[u8]) -> Result<Self, InternalError>;
+    fn hash_to_curve<H: BlockInput + Digest>(msg: &[u8], dst: &[u8])
+        -> Result<Self, InternalError>;
 
     /// Hashes a slice of pseudo-random bytes to a scalar
-    fn hash_to_scalar<H: Hash>(input: &[u8], dst: &[u8]) -> Result<Self::Scalar, InternalError>;
+    fn hash_to_scalar<H: BlockInput + Digest>(
+        input: &[u8],
+        dst: &[u8],
+    ) -> Result<Self::Scalar, InternalError>;
 
     /// The type of base field scalars
     type Scalar: Zeroize

src/group/p256.rs

@@ -15,9 +15,9 @@
 
 use super::Group;
 use crate::errors::InternalError;
-use crate::hash::Hash;
 use core::ops::{Add, Div, Mul, Neg};
 use core::str::FromStr;
+use digest::{BlockInput, Digest};
 use generic_array::typenum::{U32, U33};
 use generic_array::{ArrayLength, GenericArray};
 use num_bigint::{BigInt, Sign};
@@ -41,7 +41,10 @@ impl Group for ProjectivePoint {
 
     // Implements the `hash_to_curve()` function from
     // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-3
-    fn hash_to_curve<H: Hash>(msg: &[u8], dst: &[u8]) -> Result<Self, InternalError> {
+    fn hash_to_curve<H: BlockInput + Digest>(
+        msg: &[u8],
+        dst: &[u8],
+    ) -> Result<Self, InternalError> {
         // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-8.2
         // `p: 2^256 - 2^224 + 2^192 + 2^96 - 1`
         const P: Lazy<BigInt> = Lazy::new(|| {
@@ -89,7 +92,10 @@ impl Group for ProjectivePoint {
 
     // Implements the `HashToScalar()` function from
     // https://www.ietf.org/archive/id/draft-irtf-cfrg-voprf-07.html#section-4.3
-    fn hash_to_scalar<H: Hash>(input: &[u8], dst: &[u8]) -> Result<Self::Scalar, InternalError> {
+    fn hash_to_scalar<H: BlockInput + Digest>(
+        input: &[u8],
+        dst: &[u8],
+    ) -> Result<Self::Scalar, InternalError> {
         // https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf#[{%22num%22:211,%22gen%22:0},{%22name%22:%22XYZ%22},70,700,0]
         // P-256 `n` is defined as `115792089210356248762697446949407573529996955224135760342 422259061068512044369`
         const N: Lazy<BigInt> = Lazy::new(|| {

src/group/ristretto.rs

@@ -7,7 +7,6 @@
 
 use super::Group;
 use crate::errors::InternalError;
-use crate::hash::Hash;
 use core::convert::TryInto;
 use curve25519_dalek::{
     constants::RISTRETTO_BASEPOINT_POINT,
@@ -15,6 +14,7 @@ use curve25519_dalek::{
     scalar::Scalar,
     traits::Identity,
 };
+use digest::{BlockInput, Digest};
 use generic_array::{typenum::U32, GenericArray};
 use rand::{CryptoRng, RngCore};
 use subtle::ConstantTimeEq;
@@ -25,7 +25,10 @@ impl Group for RistrettoPoint {
 
     // 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: Hash>(msg: &[u8], dst: &[u8]) -> Result<Self, InternalError> {
+    fn hash_to_curve<H: BlockInput + Digest>(
+        msg: &[u8],
+        dst: &[u8],
+    ) -> Result<Self, InternalError> {
         let uniform_bytes = super::expand::expand_message_xmd::<H>(msg, dst, 64)?;
 
         Ok(RistrettoPoint::from_uniform_bytes(
@@ -38,7 +41,10 @@ impl Group for RistrettoPoint {
 
     // Implements the `HashToScalar()` function from
     // https://www.ietf.org/archive/id/draft-irtf-cfrg-voprf-07.html#section-4.1
-    fn hash_to_scalar<H: Hash>(input: &[u8], dst: &[u8]) -> Result<Self::Scalar, InternalError> {
+    fn hash_to_scalar<H: BlockInput + Digest>(
+        input: &[u8],
+        dst: &[u8],
+    ) -> Result<Self::Scalar, InternalError> {
         let uniform_bytes = super::expand::expand_message_xmd::<H>(input, dst, 64)?;
 
         Ok(Scalar::from_bytes_mod_order_wide(

src/group/tests.rs

@@ -9,42 +9,41 @@
 
 use crate::errors::InternalError;
 use crate::group::Group;
-use crate::CipherSuite;
 
 // Test that the deserialization of a group element should throw an error
 // if the identity element can be deserialized properly
 
 #[test]
 fn test_group_properties() -> Result<(), InternalError> {
-    use crate::tests::Ristretto255Sha512;
+    use curve25519_dalek::ristretto::RistrettoPoint;
 
-    test_identity_element_error::<Ristretto255Sha512>()?;
-    test_zero_scalar_error::<Ristretto255Sha512>()?;
+    test_identity_element_error::<RistrettoPoint>()?;
+    test_zero_scalar_error::<RistrettoPoint>()?;
 
     #[cfg(feature = "p256")]
     {
-        use crate::tests::P256Sha256;
+        use p256_::ProjectivePoint;
 
-        test_identity_element_error::<P256Sha256>()?;
-        test_zero_scalar_error::<P256Sha256>()?;
+        test_identity_element_error::<ProjectivePoint>()?;
+        test_zero_scalar_error::<ProjectivePoint>()?;
     }
 
     Ok(())
 }
 
 // Checks that the identity element cannot be deserialized
-fn test_identity_element_error<CS: CipherSuite>() -> Result<(), InternalError> {
-    let identity = CS::Group::identity();
-    let result = CS::Group::from_element_slice(&identity.to_arr());
+fn test_identity_element_error<G: Group>() -> Result<(), InternalError> {
+    let identity = G::identity();
+    let result = G::from_element_slice(&identity.to_arr());
     assert!(matches!(result, Err(InternalError::PointError)));
 
     Ok(())
 }
 
 // Checks that the zero scalar cannot be deserialized
-fn test_zero_scalar_error<CS: CipherSuite>() -> Result<(), InternalError> {
-    let zero_scalar = CS::Group::scalar_zero();
-    let result = CS::Group::from_scalar_slice(&CS::Group::scalar_as_bytes(zero_scalar));
+fn test_zero_scalar_error<G: Group>() -> Result<(), InternalError> {
+    let zero_scalar = G::scalar_zero();
+    let result = G::from_scalar_slice(&G::scalar_as_bytes(zero_scalar));
     assert!(matches!(result, Err(InternalError::ZeroScalarError)));
 
     Ok(())