Adding a hash type to CipherSuite (#24)

src/slow_hash.rs

@@ -6,29 +6,36 @@
 //! Trait specifying a slow hashing function
 
 use crate::errors::InternalPakeError;
-
-use generic_array::{typenum::U32, GenericArray};
+use crate::hash::Hash;
+use digest::Digest;
+use generic_array::GenericArray;
 
 /// Used for the slow hashing function in OPAQUE
-pub trait SlowHash {
+pub trait SlowHash<D: Hash> {
     /// Computes the slow hashing function
-    fn hash(input: GenericArray<u8, U32>) -> Result<Vec<u8>, InternalPakeError>;
+    fn hash(
+        input: GenericArray<u8, <D as Digest>::OutputSize>,
+    ) -> Result<Vec<u8>, InternalPakeError>;
 }
 
 /// A no-op hash which simply returns its input
 pub struct NoOpHash;
 
-impl SlowHash for NoOpHash {
-    fn hash(input: GenericArray<u8, U32>) -> Result<Vec<u8>, InternalPakeError> {
+impl<D: Hash> SlowHash<D> for NoOpHash {
+    fn hash(
+        input: GenericArray<u8, <D as Digest>::OutputSize>,
+    ) -> Result<Vec<u8>, InternalPakeError> {
         Ok(input.to_vec())
     }
 }
 
 #[cfg(feature = "slow-hash")]
-impl SlowHash for scrypt::ScryptParams {
-    fn hash(input: GenericArray<u8, U32>) -> Result<Vec<u8>, InternalPakeError> {
+impl<D: Hash> SlowHash<D> for scrypt::ScryptParams {
+    fn hash(
+        input: GenericArray<u8, <D as Digest>::OutputSize>,
+    ) -> Result<Vec<u8>, InternalPakeError> {
         let params = scrypt::ScryptParams::new(15, 8, 1).unwrap();
-        let mut output = [0u8; 32];
+        let mut output = [0u8; <D as Digest>::OutputSize::to_usize()];
         scrypt::scrypt(&input, &[], &params, &mut output)
             .map_err(|_| InternalPakeError::SlowHashError)?;
         Ok(output.to_vec())