n2rng_getentropy
rv = n2rng_getentropy(n2rng, (void *)frsp->XKEY, ROUNDUP(SHA1BYTES, 8));
if ((rv = n2rng_getentropy(n2rng, (void *)&entropy.as64[1],
int n2rng_getentropy(n2rng_t *n2rng, void *buffer, size_t size);