gcm_calculate_auth_mac
gcm_calculate_auth_mac(req, dg, assoclen);
gcm_calculate_auth_mac(req, dg, assoclen);
gcm_calculate_auth_mac(req, dg, assoclen);
gcm_calculate_auth_mac(req, dg, assoclen);
gcm_calculate_auth_mac(req, ghash);