crypto_prng
__CTASSERT(sizeof(struct crypto_prng) == crypto_prng_SEEDBYTES);
crypto_prng_seed(struct crypto_prng *prng, const void *seed)
crypto_prng_buf(struct crypto_prng *prng, void *buf, size_t n)
struct crypto_prng prng;
struct crypto_prng arc4_prng;