Module esp32_hal::rng

Random Number Generator

Overview

The Random Number Generator (RNG) Driver for ESP chips is a software module that 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.

The RNG peripheral on ESP chips produces random numbers based on physical noise sources, which provide true random numbers under specific conditions (see conditions below).

To use the Rng Driver, you need to initialize it with the RNG peripheral. Once initialized, you can generate random numbers by calling the random method, which returns a 32-bit unsigned integer.

Additionally, this driver implements the Read trait from the embedded_hal crate, allowing you to generate random bytes by calling the read method.

Important Note

There are certain pre-conditions which must be met in order for the RNG to produce true random numbers. 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 internal entropy source has been enabled by calling bootloader_random_enable() and not yet disabled by calling bootloader_random_disable().
• While the ESP-IDF Second stage bootloader is running. This is because the default ESP-IDF bootloader implementation calls bootloader_random_enable() when the bootloader starts, and bootloader_random_disable() before executing the app.

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.

For more information, please refer to the ESP-IDF documentation:
https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/random.html

Examples

Initialization

let mut rng = Rng::new(peripherals.RNG);

Generate a random word (u32)

let random: u32 = rng.random();

Fill a buffer of arbitrary size with random bytes

let mut buffer = [0u8; 32];
rng.read(&mut buffer).unwrap();

Structs

• Rng
  Random number generator driver