示例#1
0
/**
 * Generate a truly random KUID within given `kuid'.
 */
void
kuid_random_fill(kuid_t *kuid)
{
	struct sha1 entropy;
	bigint_t bk, be;

	/*
	 * Entropy collection is slow but we generate our KUID only at startup
	 * and when none was present (nodes reuse their KUID from session to
	 * session to reuse as much of their previous routing table as possible).
	 *
	 * The aim is to obtain the most random KUID to ensure that among all
	 * the peers in the Kademlia network, KUIDs are unique and uniformly
	 * distributed in the KUID space.
	 */

	entropy_collect(&entropy);				/* slow */
	random_strong_bytes(kuid->v, KUID_RAW_SIZE);

	/*
	 * Combine the two random numbers by adding them.
	 *
	 * It's slightly better than XOR-ing the two since the propagation
	 * of the carry bit diffuses the randomness (entropy remains the same).
	 */

	STATIC_ASSERT(sizeof kuid->v == sizeof entropy.data);

	bigint_use(&bk, kuid->v, sizeof kuid->v);
	bigint_use(&be, entropy.data, sizeof entropy.data);

	(void) bigint_add(&bk, &be);
}
示例#2
0
/**
 * Add entropy from previous calls.
 */
static G_GNUC_COLD void
entropy_merge(sha1_t *digest)
{
	bigint_t older, newer;

	/*
	 * These big integers operate on the buffer space from ``digest'' and
	 * ``entropy_previous'' directly.
	 */

	bigint_use(&older, &entropy_previous, SHA1_RAW_SIZE);
	bigint_use(&newer, digest, SHA1_RAW_SIZE);
	bigint_add(&newer, &older);
	bigint_copy(&older, &newer);
}