Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?

Latest commit


Git stats


Failed to load latest commit information.

mirage-crypto - Cryptographic primitives for MirageOS


mirage-crypto is a small cryptographic library that puts emphasis on the applicative style and ease of use. It includes basic ciphers (AES, 3DES, RC4, ChaCha20/Poly1305), hashes (MD5, SHA1, SHA2 family), AEAD primitives (AES-GCM, AES-CCM), public-key primitives (RSA, DSA, DH) and a strong RNG (Fortuna).

RSA timing attacks are countered by blinding. AES timing attacks are avoided by delegating to AES-NI.

Mirage-crypto is a fork of the ocaml-nocrypto written by David Kaloper. It was forked with the permission of the original author in order to facilitate changes (e.g. build system) required by Mirage that the upstream didn't have time to keep up with.

Mirage-crypto-rng embeds the former mirage-entropy opam package, which implements various entropy sources:

  • non-deterministic execution time (used at initial seeding, see the whirlwind RNG paper)
  • a hook into the Lwt event loop that collects a timestamp of each event
  • rdseed and rdrand (x86/x86-64 only)

API documentation online


dune build
dune runtest


RNG seeding

If RNG fails with Fatal error: exception Unseeded_generator, you need to seed it.


let () = Mirage_crypto_rng_lwt.initialize (module Mirage_crypto_rng.Fortuna)


let () = Mirage_crypto_rng_unix.initialize (module Mirage_crypto_rng.Fortuna)