Merge pull request #96 from dlblv/fix/add-secret-as-bytes

Add `.as_bytes()` method for `StaticSecret`

benches/x25519.rs

@@ -25,12 +25,12 @@ use x25519_dalek::EphemeralSecret;
 use x25519_dalek::PublicKey;
 
 fn bench_diffie_hellman(c: &mut Criterion) {
-    let bob_secret = EphemeralSecret::new(&mut OsRng);
+    let bob_secret = EphemeralSecret::new(OsRng);
     let bob_public = PublicKey::from(&bob_secret);
 
     c.bench_function("diffie_hellman", move |b| {
         b.iter_with_setup(
-            || EphemeralSecret::new(&mut OsRng),
+            || EphemeralSecret::new(OsRng),
             |alice_secret| alice_secret.diffie_hellman(&bob_public),
         )
     });

src/x25519.rs

@@ -60,6 +60,14 @@ impl PublicKey {
     }
 }
 
+impl AsRef<[u8]> for PublicKey {
+    /// View this public key as a byte array.
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        self.as_bytes()
+    }
+}
+
 /// A short-lived Diffie-Hellman secret key that can only be used to compute a single
 /// [`SharedSecret`].
 ///
@@ -174,7 +182,7 @@ impl StaticSecret {
     /// Perform a Diffie-Hellman key agreement between `self` and
     /// `their_public` key to produce a `SharedSecret`.
     pub fn diffie_hellman(&self, their_public: &PublicKey) -> SharedSecret {
-        SharedSecret(&self.0 * their_public.0)
+        SharedSecret(self.0 * their_public.0)
     }
 
     /// Generate an x25519 key.
@@ -187,9 +195,16 @@ impl StaticSecret {
     }
 
     /// Extract this key's bytes for serialization.
+    #[inline]
     pub fn to_bytes(&self) -> [u8; 32] {
         self.0.to_bytes()
     }
+
+    /// View this key as a byte array.
+    #[inline]
+    pub fn as_bytes(&self) -> &[u8; 32] {
+        self.0.as_bytes()
+    }
 }
 
 impl From<[u8; 32]> for StaticSecret {
@@ -206,6 +221,14 @@ impl<'a> From<&'a StaticSecret> for PublicKey {
     }
 }
 
+impl AsRef<[u8]> for StaticSecret {
+    /// View this key as a byte array.
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        self.as_bytes()
+    }
+}
+
 /// The result of a Diffie-Hellman key exchange.
 ///
 /// Each party computes this using their [`EphemeralSecret`] or [`StaticSecret`] and their
@@ -266,6 +289,14 @@ impl SharedSecret {
     }
 }
 
+impl AsRef<[u8]> for SharedSecret {
+    /// View this shared secret key as a byte array.
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        self.as_bytes()
+    }
+}
+
 /// "Decode" a scalar from a 32-byte array.
 ///
 /// By "decode" here, what is really meant is applying key clamping by twiddling