Hasher trait not implemented for digests

[PlasmaPower]

The std::hash::Hasher trait is not implemented for these digests. The trait is identical to the digest::Input and digest::FixedOutput traits. Implementing it would be useful for me, because I'd like to have my std::hash::Hash implementation be usable with a digest::Digest.

[PlasmaPower]

Oh, I just noticed that the digest::*Output traits take self, whereas std::hash::Hasher::finish takes &self. That will be a problem.

[newpavlov]

Hasher is a really bad fit for crypto hash functions. See for example this comment and the following discussion.

[newpavlov]

One way to circumvent this in your code is to define your generic wrapper type and implement Hasher for it:

struct MyDigest<D: Digest> {
    d: D
}

impl<D: Digest> Hasher for MyDigest<D> {
    // ..
}

[PlasmaPower]

I ended up using a similar solution. Perhaps we could add a method to the digest::Input trait to accept std::hash::Hash objects.

[newpavlov]

In that case I will close this issue as we currently don't have plans regarding implementing Hasher. Take a look at this issue, in which we discuss crate for recursively hashing structs. maybe you'll find mzabaluev/digest-hash crate useful.