noise_mix_hash
noise_mix_hash(hash, tmp, NOISE_HASH_LEN);
noise_mix_hash(hash, s, NOISE_PUBLIC_KEY_LEN);
noise_mix_hash(hash, dst, src_len + NOISE_AUTHTAG_LEN);
noise_mix_hash(hash, src, src_len);
noise_mix_hash(hash, src, NOISE_PUBLIC_KEY_LEN);
static void noise_mix_hash(uint8_t [NOISE_HASH_LEN], const uint8_t *, size_t);