Update to draft 19 (#101)

src/group/ristretto.rs

@@ -10,7 +10,7 @@ use curve25519_dalek::ristretto::{CompressedRistretto, RistrettoPoint};
 use curve25519_dalek::scalar::Scalar;
 use curve25519_dalek::traits::Identity;
 use digest::core_api::BlockSizeUser;
-use digest::Digest;
+use digest::{FixedOutput, HashMarker};
 use elliptic_curve::hash2curve::{ExpandMsg, ExpandMsgXmd, Expander};
 use generic_array::typenum::{IsLess, IsLessOrEqual, U256, U32, U64};
 use generic_array::GenericArray;
@@ -26,7 +26,7 @@ pub struct Ristretto255;
 
 #[cfg(feature = "ristretto255-ciphersuite")]
 impl crate::CipherSuite for Ristretto255 {
-    const ID: u16 = 0x0001;
+    const ID: &'static str = "ristretto255-SHA512";
 
     type Group = Ristretto255;
 
@@ -44,9 +44,9 @@ 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>(input: &[&[u8]], dst: &[u8]) -> Result<Self::Elem, InternalError>
+    fn hash_to_curve<H>(input: &[&[u8]], dst: &[&[u8]]) -> Result<Self::Elem, InternalError>
     where
-        H: Digest + BlockSizeUser,
+        H: BlockSizeUser + Default + FixedOutput + HashMarker,
         H::OutputSize: IsLess<U256> + IsLessOrEqual<H::BlockSize>,
     {
         let mut uniform_bytes = GenericArray::<_, U64>::default();
@@ -59,9 +59,9 @@ impl Group for Ristretto255 {
 
     // 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>(input: &[&[u8]], dst: &[u8]) -> Result<Self::Scalar, InternalError>
+    fn hash_to_scalar<H>(input: &[&[u8]], dst: &[&[u8]]) -> Result<Self::Scalar, InternalError>
     where
-        H: Digest + BlockSizeUser,
+        H: BlockSizeUser + Default + FixedOutput + HashMarker,
         H::OutputSize: IsLess<U256> + IsLessOrEqual<H::BlockSize>,
     {
         let mut uniform_bytes = GenericArray::<_, U64>::default();