I started once to give it a try. I agree it looks easy enough for the digest methods/trait
I gave up because I don't have not enough Rust-fu. Still learning.
I think I gave up when I tried to turn DigestBytes into GenericArrays. Didn't want to copy stuff around.
Copying into a GenericArray shouldn't be a problem, because they're 16-20 bytes large, and returned by value anyway. LLVM may be able to optimize that out.