Mirage_crypto_rng_unixSourceRNG seeding on Unix.
This module initializes a Fortuna RNG with getrandom(), and CPU RNG. On BSD systems (FreeBSD, OpenBSD, macOS) getentropy () is used instead of getrandom (). On Windows 10 or higher, BCryptGenRandom() is used with the default RNG. Windows 8 or lower are not supported by this library.
initialize ~g rng will bring the RNG into a working state.
getrandom size returns a buffer of size filled with random bytes.