With this example we are going to demonstrate how to generate a Message Authentication Code (MAC). We are using the Mac class that provides the functionality of a “Message Authentication Code” (MAC) algorithm. In short, to generate a Message Authentication Code you should:
- Create a new KeyGenerator for the
HmacMD5algorithm. - Generate a SecretKey, using
generateKey()API method of KeyGenerator. - Create a Mac object.
- Initialize the MAC with the above key, using
init(Key key)API method of Mac. - Create a new String message and get its byte array.
- Use
doFinal(byte[] input)API method of Mac to process the given array of bytes and finish the MAC operation.
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core;
import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import javax.crypto.KeyGenerator;
import javax.crypto.Mac;
import javax.crypto.SecretKey;
public class GenerateMessageAuthenticationCode {
public static void main(String[] args) {
try {
// get a key generator for the HMAC-MD5 keyed-hashing algorithm
KeyGenerator keyGen = KeyGenerator.getInstance("HmacMD5");
// generate a key from the generator
SecretKey key = keyGen.generateKey();
// create a MAC and initialize with the above key
Mac mac = Mac.getInstance(key.getAlgorithm());
mac.init(key);
String message = "This is a confidential message";
// get the string as UTF-8 bytes
byte[] b = message.getBytes("UTF-8");
// create a digest from the byte array
byte[] digest = mac.doFinal(b);
}
catch (NoSuchAlgorithmException e) {
System.out.println("No Such Algorithm:" + e.getMessage());
return;
}
catch (UnsupportedEncodingException e) {
System.out.println("Unsupported Encoding:" + e.getMessage());
return;
}
catch (InvalidKeyException e) {
System.out.println("Invalid Key:" + e.getMessage());
return;
}
}
}
This was an example of how to generate a Message Authentication Code (MAC) in Java.
