trezor-firmware/embed/extmod/modtrezorcrypto/rand.c

/*
 * Copyright (c) Pavol Rusnak, SatoshiLabs
 *
 * Licensed under TREZOR License
 * see LICENSE file for details
 */

#include "rand.h"
#include "rng.h"

uint32_t random32(void)
{
	return rng_get();
}

uint32_t random_uniform(uint32_t n)
{
	uint32_t x, max = 0xFFFFFFFF - (0xFFFFFFFF % n);
	while ((x = random32()) >= max);
	return x / (max / n);
}

void random_buffer(uint8_t *buf, size_t len)
{
	uint32_t r = 0;
	for (size_t i = 0; i < len; i++) {
		if (i % 4 == 0) {
			r = random32();
		}
		buf[i] = (r >> ((i % 4) * 8)) & 0xFF;
	}
}