if ( type == PacSignature.KERB_CHECKSUM_HMAC_MD5 ) {
                KerberosKey key = keys.get(PacSignature.ETYPE_ARCFOUR_HMAC);
                if ( key == null ) {
                    throw new PACDecodingException("Missing key");
                }
                return calculateMacArcfourHMACMD5(usage, key, data);
            }