private String generateSignature() {
		if (this.cert.equals("") || this.cert == null) {
			Utilities.log(Level.SEVERE, "NO CERTIFICATE FOUND!");
		}
		// generate a SHA1-HMAC signature
		String sig = "";
		try {
			SecretKeySpec key = new SecretKeySpec(this.userCode.getBytes("UTF-8"), "HmacSHA1");
			Mac mac = Mac.getInstance("HmacSHA1");
			mac.init(key);

			sig = this.byteArrayToHex(mac.doFinal(this.cert.getBytes("UTF-8")));
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (InvalidKeyException e) {
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}

		return sig;
	}