return hmac.digest();
        } catch (UnsupportedEncodingException uee) {
            throw new RuntimeException(uee.getMessage());
        }
    }
    static byte[] computeResponse(byte[] responseKey,
                byte[] serverChallenge,
                byte[] clientData,
                int offset,
                int length)
    {
        HMACT64 hmac = new HMACT64(responseKey);