HMAC Util for packet encryption and to prevent message tampering

HmacUtil.class

package in.co.teni.service.banking.util;

import java.io.IOException;
import java.math.BigDecimal;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;
import org.apache.http.HttpException;
import org.codehaus.jackson.map.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import in.co.teni.service.banking.ecollect.model.NotificationRequest;
import in.co.teni.service.banking.ecollect.model.ValidationRequest;

public class HmacUtil {

	private final static String HMAC_SHA1_ALGORITHM = "HmacSHA1";

	private static final Logger logger = LoggerFactory.getLogger(HmacUtil.class);

	public static void main(String[] args) throws HttpException, IOException, NoSuchAlgorithmException {

		String clientKey = "";
		String clientSecret = "";

		System.out.println("Client ID is " + clientKey + " and client secret is " + clientSecret );

		ValidationRequest validationRequest = new ValidationRequest();
		validationRequest.setAmount(new BigDecimal(10000));
		validationRequest.setTxnRefId("P16111764473891");
		validationRequest.setAccountNumber("SHOPXDT051624");
		String stringValidationRequest = new ObjectMapper().writeValueAsString(validationRequest);
		String messageDigestValidationRequest = calculateMD5(stringValidationRequest);
		String hmacValidationRequest = calculateHMAC(clientSecret, messageDigestValidationRequest);

		System.out.println("\n For validation request, " + stringValidationRequest + " message digest and hmac value is "
				+ messageDigestValidationRequest + " " + hmacValidationRequest);

		NotificationRequest notificationRequest = new NotificationRequest();
		notificationRequest.setTxnRefId("P16111764473891");
		notificationRequest.setTxnStatus("SUCCESS");
		notificationRequest.setTxnRemark("Payment has been successfully acknowledged and transferred to the shopx account.");
		notificationRequest.setUtrNumber("PBVD11764972802");
		String stringNotificationRequest = new ObjectMapper().writeValueAsString(notificationRequest);

		String messageDigestNotificationRequest = calculateMD5(stringNotificationRequest);
		String hmacNotificationRequest = calculateHMAC(clientSecret, messageDigestNotificationRequest);

		System.out.println("\n For notification request, " + stringNotificationRequest + " message digest and hmac value is " 
				+ messageDigestNotificationRequest + " " + hmacNotificationRequest);
	}

	public static String calculateHMAC(String secret, String data) {
		try {
			SecretKeySpec signingKey = new SecretKeySpec(secret.getBytes(),	HMAC_SHA1_ALGORITHM);
			Mac mac = Mac.getInstance(HMAC_SHA1_ALGORITHM);
			mac.init(signingKey);
			byte[] rawHmac = mac.doFinal(data.getBytes());
			return new String(Base64.encodeBase64(rawHmac));
		} catch (GeneralSecurityException e) {
			logger.warn("Unexpected error while creating hash: " + e.getMessage(),	e);
			return null;
		} catch (Exception e){
			logger.error("Unknown Exception occurred while doing the HMAC Calculation", e);
			return null;
		}
	}

	public static String calculateMD5(String contentToEncode) throws NoSuchAlgorithmException {
		MessageDigest digest = MessageDigest.getInstance("MD5");
		digest.update(contentToEncode.getBytes());
		return new String(Base64.encodeBase64(digest.digest()));
	}

}