cryptokit
A library of cryptographic primitive -- block ciphers (AES, DES, 3DES), stream ciphers (ARCfour), public-key crypto (RSA, DH), hashes (SHA-1, SHA-256), MACs, random number generation -- all presented with a compositional, extensible interface.
Original source at: http://forge.ocamlcore.org/frs/?group_id=133