dh_unpack_data
ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
ptr = dh_unpack_data(¶ms->key_size, ptr, sizeof(params->key_size));
ptr = dh_unpack_data(¶ms->p_size, ptr, sizeof(params->p_size));
ptr = dh_unpack_data(¶ms->g_size, ptr, sizeof(params->g_size));