RNGSTATE_SIZE
memcpy(rng.state, digest, RNGSTATE_SIZE);
memcpy(rng.data, digest + RNGSTATE_SIZE, RNGDATA_SIZE);
SHA512_Update(&ctx, rng.state, RNGSTATE_SIZE);
memcpy(rng.state, digest, RNGSTATE_SIZE);
memcpy(rng.data, digest + RNGSTATE_SIZE, RNGDATA_SIZE);
uint8_t state[RNGSTATE_SIZE];