Address review comments

- Add that we treat BLAKE2b as a random oracle to the comment
- Avoid unnecessary array allocation

src/scalar/dusk.rs

@@ -265,7 +265,8 @@ impl Scalar {
     /// BLAKE2b into a 512-bits number, and then converting the number into its
     /// `Scalar` representation by reducing it by the modulo.
     ///
-    /// This implementation follows the first conversion of
+    /// By treating the output of the BLAKE2b hash as a random oracle, this
+    /// implementation follows the first conversion of
     /// https://hackmd.io/zV6qe1_oSU-kYU6Tt7pO7Q with concrete numbers:
     /// ```text
     /// p = 0x73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001
@@ -285,10 +286,18 @@ impl Scalar {
             .update(input)
             .finalize();
 
-        let mut bytes = [0u8; 64];
-        bytes.copy_from_slice(&state.as_bytes()[..64]);
-
-        Self::from_bytes_wide(&bytes)
+        let bytes = state.as_bytes();
+
+        Scalar::from_u512([
+            u64::from_le_bytes(<[u8; 8]>::try_from(&bytes[0..8]).unwrap()),
+            u64::from_le_bytes(<[u8; 8]>::try_from(&bytes[8..16]).unwrap()),
+            u64::from_le_bytes(<[u8; 8]>::try_from(&bytes[16..24]).unwrap()),
+            u64::from_le_bytes(<[u8; 8]>::try_from(&bytes[24..32]).unwrap()),
+            u64::from_le_bytes(<[u8; 8]>::try_from(&bytes[32..40]).unwrap()),
+            u64::from_le_bytes(<[u8; 8]>::try_from(&bytes[40..48]).unwrap()),
+            u64::from_le_bytes(<[u8; 8]>::try_from(&bytes[48..56]).unwrap()),
+            u64::from_le_bytes(<[u8; 8]>::try_from(&bytes[56..64]).unwrap()),
+        ])
     }
 
     /// SHR impl