Hash algorithms in OCaml

Digestif (and Rakia) provid some hashes functions in OCaml. Rakia provides theses functions by a C stub and Digestif is a pure implementation in OCaml of theses hashes. So these hashes functions can be used in an OCaml/Mirage/JavasScript world.

Obviously, Rakia is more faster than Digestif (the hot loop was implemented in C) but it's possible than Rakia can't compile in your architecture. In this case, it's better to use Digestif or send a PR to fix Rakia.

Documentation: http://mirage.github.io/digestif/api.docdir/

API

We provide an interface with no dependancy (only with Bigarray, available by the OCaml distribution). You can choose between the Bytes module or the Bigstring module. You can't remove the dependancy with Bigarray because the context of the hash function is internally a Bigarray.Array1.t.

We provide the same interface:

type t
type ctx
type buffer

val init    : unit -> ctx
val feed    : ctx -> buffer -> unit
val get     : ctx -> t

val digest  : buffer -> t
val digestv : buffer list -> t
val hmac    : key:buffer -> buffer -> t
val hmacv   : key:buffer -> buffer list -> t

val compare : t -> t -> int
val eq      : t -> t -> bool
val neq     : t -> t -> bool

val pp      : Format.formatter -> t -> unit
val of_hex  : buffer -> t
val to_hex  : t -> buffer

buffer can be a Bytes.t or a Bigstring.t. We have an imperative and a functionnal way to produce a hash. t is not equivalent between the module Bytes and the module Bigstring.

Hashes functions

At this time, we implemented these hashes:

• SHA1
• SHA224
• SHA256
• SHA384
• SHA512
• BLAKE2B

If you want an other hash function, you can ask in the issue.

Build Requirements

• OCaml >= 4.03.0 (may be less but need test)
• base-bytes meta-package
• Bigarray module (provided by the standard library of OCaml)
• topkg, ocamlbuild and ocamlfind 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

We deleted the cstruct hard dependancy (from nocrypto) and provide a interface to compute with the Bytes.t. We add the blake2b implementation too and we have the plan to provide the hash function in pure OCaml and other hashes functions. Finally, you can use nocrypto and digestif together (no clash name in the C stub, don't worry).

So, yes, it's redundant but deal with it!