SIP_U8TO64_LE
key->k[0] = SIP_U8TO64_LE((const unsigned char *)src);
key->k[1] = SIP_U8TO64_LE((const unsigned char *)src + 8);
m = SIP_U8TO64_LE(H->buf);
if (siphash24(in, i, &k) != SIP_U8TO64_LE(vectors[i]))