feat: functionality to work with Hidden types (#148)

* Functionality to work with `Hidden` types

* Formatting

src/hashing.rs

@@ -31,7 +31,7 @@
 use std::{marker::PhantomData, ops::Deref};
 
 use blake2::VarBlake2b;
-use digest::{Digest, Output, Update};
+use digest::{Digest, FixedOutput, Output, Update};
 use sha3::Sha3_256;
 use tari_utilities::ByteArray;
 
@@ -306,6 +306,20 @@ pub trait AsFixedBytes<const I: usize>: AsRef<[u8]> {
 
 impl<const I: usize, D: Digest> AsFixedBytes<I> for DomainSeparatedHash<D> {}
 
+impl<TInnerDigest: FixedOutput, TDomain: DomainSeparation> FixedOutput
+    for DomainSeparatedHasher<TInnerDigest, TDomain>
+{
+    type OutputSize = TInnerDigest::OutputSize;
+
+    fn finalize_into(self, out: &mut digest::generic_array::GenericArray<u8, Self::OutputSize>) {
+        self.inner.finalize_into(out);
+    }
+
+    fn finalize_into_reset(&mut self, out: &mut digest::generic_array::GenericArray<u8, Self::OutputSize>) {
+        self.inner.finalize_into_reset(out);
+    }
+}
+
 /// Implements Digest so that it can be used for other crates
 impl<TInnerDigest: Digest, TDomain: DomainSeparation> Digest for DomainSeparatedHasher<TInnerDigest, TDomain> {
     type OutputSize = TInnerDigest::OutputSize;
@@ -571,7 +585,7 @@ pub fn create_hasher<D: Digest, HD: DomainSeparation>() -> DomainSeparatedHasher
 #[cfg(test)]
 mod test {
     use blake2::Blake2b;
-    use digest::Digest;
+    use digest::{generic_array::GenericArray, Digest, FixedOutput};
     use tari_utilities::hex::{from_hex, to_hex};
 
     use crate::{
@@ -628,6 +642,26 @@ mod test {
         assert_eq!(MacDomain::domain_separation_tag("test"), "com.tari.mac.v1.test");
     }
 
+    #[test]
+    fn finalize_into() {
+        hash_domain!(TestHasher, "com.example.test");
+        let mut hasher = DomainSeparatedHasher::<Blake256, TestHasher>::new();
+        hasher.update([0, 0, 0]);
+
+        let mut output = GenericArray::<u8, <Blake256 as Digest>::OutputSize>::default();
+        hasher.finalize_into(&mut output);
+    }
+
+    #[test]
+    fn finalize_into_reset() {
+        hash_domain!(TestHasher, "com.example.test");
+        let mut hasher = DomainSeparatedHasher::<Blake256, TestHasher>::new();
+        hasher.update([0, 0, 0]);
+
+        let mut output = GenericArray::<u8, <Blake256 as Digest>::OutputSize>::default();
+        hasher.finalize_into_reset(&mut output);
+    }
+
     #[test]
     fn dst_hasher() {
         hash_domain!(GenericHashDomain, "com.tari.generic");

src/keys.rs

@@ -11,6 +11,7 @@ use std::ops::Add;
 use rand::{CryptoRng, Rng};
 use serde::{de::DeserializeOwned, ser::Serialize};
 use tari_utilities::ByteArray;
+use zeroize::Zeroize;
 
 /// A trait specifying common behaviour for representing `SecretKey`s. Specific elliptic curve
 /// implementations need to implement this trait for them to be used in Tari.
@@ -26,7 +27,7 @@ use tari_utilities::ByteArray;
 /// let k = RistrettoSecretKey::random(&mut rng);
 /// let p = RistrettoPublicKey::from_secret_key(&k);
 /// ```
-pub trait SecretKey: ByteArray + Clone + PartialEq + Eq + Add<Output = Self> + Default {
+pub trait SecretKey: ByteArray + Clone + PartialEq + Eq + Add<Output = Self> + Default + Zeroize {
     /// The length of the key, in bytes
     fn key_length() -> usize;
     /// Generates a random secret key
@@ -40,7 +41,7 @@ pub trait SecretKey: ByteArray + Clone + PartialEq + Eq + Add<Output = Self> + D
 ///
 /// See [SecretKey](trait.SecretKey.html) for an example.
 pub trait PublicKey:
-    ByteArray + Add<Output = Self> + Clone + PartialOrd + Ord + Default + Serialize + DeserializeOwned
+    ByteArray + Add<Output = Self> + Clone + PartialOrd + Ord + Default + Serialize + DeserializeOwned + Zeroize
 {
     /// The output size len of Public Key
     const KEY_LEN: usize;