RIPEMD-256 implementation

[gavadinov]

Partially addresses #1

A RIPEMD-256 implementation based on the existing RIPEMD-320 implementation and https://android.googlesource.com/kernel/common/+/07e6124a1a46/crypto/rmd256.c.

The test values come from - https://homes.esat.kuleuven.be/~bosselae/ripemd160.html

[tarcieri]

@gavadinov great! I'll take a look when I have some time to review

[tarcieri]

@gavadinov looks good!

I see you've already published the crate. Would you still like to upstream it here?

[gavadinov]

hey @tarcieri, thank you for the review. Yeah I had to publish it because I needed to use it. I would be happy to move it here and to change the ownership of the crate on crates.io.

[tarcieri]

@gavadinov fantastic. Does the code in this PR reflect what's published in the crate?

[newpavlov]

The code looks good (although I did only a cursory review), so think we can merge and publish it. But note that later we probably will merge the 3 ripemd crates into a single ripemd crate.

[gavadinov]

@gavadinov fantastic. Does the code in this PR reflect what's published in the crate?

Yep it is the same. Here is the original - https://github.com/gavadinov/ripemd256

But note that later we probably will merge the 3 ripemd crates into a single ripemd crate.

Yeah that makes sense. There is quite a lot of duplication between the crates.

[tarcieri]

@gavadinov cool, can you add us as owners of the ripemd256 crate?

[gavadinov]

@gavadinov cool, can you add us as owners of the ripemd256 crate?

Done

Also I noticed a typo in the keywords 🙈 - #296

[tarcieri]

Thank you!