Crate random

Available on crate feature random only.

Provides a seeded random number generator depending on Ariel OS’s configuration.

The module provides functions for use by applications, fast_rng() and crypto_rng(), which produce owned types that provide the rand_core::RngCore and rand_core::CryptoRng traits, respectively.

The crate abstracts over multiple aspects of RNGs:

• Where do we take a valid seed for the RNG from?
• What’s the type of RNG that we take along?
• Is RNG state shared across cores, threads, tasks or not at all?

No matter the choices taken (eventually through the application’s setup), all is hidden behind the FastRng and CryptoRng types.

Before accessing the RNG, it needs to be initialized through the construct_rng() function. This is taken care of by the ariel-os-embassy initialization functions. Applications can ensure that this has happened by depending on the laze feature random.

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Currently, this provides very little choice, and little fanciness: It (more or less arbitrarily) uses the rand_chacha::ChaCha20Rng generator as a shared global RNG, and rand_pcg::Pcg32 is decided yet for the fast one. Neither the algorithm nor the size of FastRng or CryptoRng is guaranteed.

Structs

• CryptoRngcsprng
  The OS provided cryptographically secure random number generator.
• FastRng
  The OS provided fast random number generator.

Functions

• construct_rng
  Populates the global RNG from a seed value.
• crypto_rngcsprng
  Returns a suitably initialized cryptographically secure random number generator.
• fast_rng
  Returns a suitably initialized fast random number generator.