Use the RustCrypto crates instead of ring?

[newpavlov]

This project already includes several RustCrypto crates via the dalek crates. As far as I can see from it you only use AES-GCM, SHA-256, HMAC, and HKDF. I think such migration will allow to simplify code and build process, as well as make the crate more portable. Of course the linked crates have several disadvantages compared to ring:

• Lack of runtime CPUID-based detection in the aes-gcm crate.
• A bit slower software implementation of SHA-256.

The latter issue can be compensated a bit by enabling the asm feature (though performance still will not be quite on par with ring). Also if CPU has SHA-extension, the crate will detect it during runtime and will use efficient intrinsic-based code.

If you have any questions regarding RustCrypto crates, I will be glad to answer them.

[woodruffw]

Thanks for the information! We don't currently have any engineers working on molasses, but we'd be happy to review any PRs that simplify both the code and the build.