Module rng 

Random Number Generator (RNG)

Overview

The Random Number Generator (RNG) module provides an interface to generate random numbers using the RNG peripheral on ESP chips. This driver allows you to generate random numbers that can be used for various cryptographic, security, or general-purpose applications.

There are certain pre-conditions which must be met in order for the RNG to produce true random numbers. For more details see Trng. The hardware RNG produces true random numbers under any of the following conditions:

• RF subsystem is enabled (i.e. Wi-Fi or Bluetooth are enabled).
• An ADC is used to generate entropy.

When any of these conditions are true, samples of physical noise are continuously mixed into the internal hardware RNG state to provide entropy. If none of the above conditions are true, the output of the RNG should be considered pseudo-random only. See Rng.

For more information, please refer to the ESP-IDF documentation.

Example

let rng = Rng::new();

// Generate a random word (u32):
let rand_word = rng.random();

// Fill a buffer with random bytes:
let mut buf = [0u8; 16];
rng.read(&mut buf);

loop {}

Compatibility with getrandom

The driver can be used directly, or integrated as a custom backend for getrandom (e.g. v0.4):

#[unsafe(no_mangle)]
unsafe extern "Rust" fn __getrandom_v04_custom(
    dest: *mut u8,
    len: usize,
) -> Result<(), Error> {
     unsafe { esp_hal::rng::Rng::new().read_into_raw(dest, len) };
     Ok(())

Structs

Rng

(Pseudo-)Random Number Generator.

Trngunstable

True Random Number Generator (TRNG)

TrngSourceunstable

Ensures random numbers are cryptographically secure.

Enums

TrngErrorunstable

Errors returned when constructing a Trng.