arc4random_prng_get
prng = arc4random_prng_get(&fallback);
prng = arc4random_prng_get(&fallback);
prng = arc4random_prng_get(&fallback);
prng = arc4random_prng_get(&fallback);
prng = arc4random_prng_get(&fallback);
prng = arc4random_prng_get(&fallback);