Digestif - Hash algorithms in C and OCaml

Digestif is a toolbox which implements hashes:

• MD5
• SHA1
• SHA2
• SHA3
• WHIRLPOOL
• BLAKE2B
• BLAKE2S
• RIPEMD160

Digestif uses a trick about linking and let the end-user to choose which implementation he wants to use. We provide 2 implementations:

• C implementation with digestif.c
• OCaml implementation with digestif.ocaml

Both are well-tested. However, OCaml implementation is slower than the C implementation.

Note: The linking trick requires digestif.c or digestif.ocaml to be the first of your dependencies.

Home page: http://blog.x25519.net/

Contact: Romain Calascibetta <romain.calascibet [email protected]>

API

For each hash, we implement the same API which is referentially transparent. Then, on the top of these, we reflect functions (like digesti or hmaci) with GADT - however, conversion from GADT to hash type is not possible (but you can destruct GADT with to_raw_string).

Equal/Compare function

We deciced to protect users to timing-attack. In this case, Digestif.equal (by eqaf package) compares hashes in constant-time.

However, we provide unsafe_compare function too which is not a constant time function. In some contexts, like ocaml-git, we don't care about timing attack and we use unsafe_compare - then, we need to make a wrap where we rename unsafe_compare to compare to be able to use it in some functors like Map.Make or Set.Make.

It's little annoying to do that but it forces the user to get the right question about security issues. So, please, don't ask to rename this function.

MirageOS

Of course, this package is available to be used on MirageOS (both implementations). User is able to compile digestif.ocaml with js_of_ocaml and this package is platform agnostic.

Build Requirements

• OCaml >= 4.03.0 (may be less but need test)
• base-bytes meta-package
• base-bigarray meta-package
• dune to build the project

If you want to compile the test program, you need:

• alcotest

Credits

This work is from the nocrypto library and the Vincent hanquez's work in ocaml-sha.

All credits appear in the begin of files and this library is motivated by two reasons:

• delete the dependancy with nocrypto if you don't use the encryption (and common) part
• aggregate all hashes functions in one library