package mirage-crypto-entropy

  1. Overview
  2. Docs
Entropy source for MirageOS unikernels


Dune Dependency





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), 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-entropy embeds the former mirage-entropy opam package, which implements various entropy sources for MirageOS unikernels:

API documentation online


dune build
dune runtest


RNG seeding

If RNG fails with Fatal error: exception Uncommon.Boot.Unseeded_generator, you need to [seed][doc-entropy] it.


let () = Mirage_crypto_rng_unix.initialize ()
Illegal instructions
Program terminated with signal SIGILL, Illegal instruction.
#0  _mm_aeskeygenassist_si128 (__C=<optimized out>, __X=...)

Mirage_crypto has CPU acceleration support (SSE2+AES-NI), but no run-time autodetection yet. You compiled the library with acceleration, but you are using it on a machine that does not support it.

The environment variable MIRAGE_CRYPTO_ACCELERATE can be used to override detection:

  • MIRAGE_CRYPTO_ACCELERATE=false dune build force-disables non-portable code.

  • MIRAGE_CRYPTO_ACCELERATE=true dune build force-enables non-portable code.

  • Otherwise, it matches the capabilities of the build machine.