Random Generators


The getrandom crate provides a low-level API around platform-specific random-number sources, and is an important building block of rand and rand_core as well as a number of cryptography libraries. It is not intended for usage outside of low-level libraries.

In some cases, particularly when targeting WASM, end-users may need to configure this crate. Consult the getrandom documentation for the relevant version.

CPU Jitter

The rand_jitter crate implements a CPU-jitter-based entropy harvester which may be used to provide an alternative source of entropy where a high-resolution CPU timer is available.

It should be noted that CPU-jitter harvesters may be prone to side-channel attacks and that this implementation is quite slow (due to conservative estimates of entropy gained per step).

In prior versions of rand this was a direct dependency, used automatically when other sources of entropy failed. In current versions it is not a dependency (not even an optional one).

Deterministic generators

The following crates implement pseudo-random number generators (see Our RNGs):

  • rand_chacha provides generators using the ChaCha cipher
  • rand_hc implements a generator using the HC-128 cipher
  • rand_isaac implements the ISAAC generators
  • rand_pcg implements a small selection of PCG generators
  • rand_xoshiro implements the SplitMix and Xoshiro generators
  • rand_xorshift implements the basic Xorshift generator