In this example we shall show you how to check message consistency using hash functions. We are using the java.security.MessageDigest Class, that provides the functionality of a message digest algorithm. It takes arbitrary-sized data and outputs a fixed-length hash value. To check the consistency of two messages using the MessageDigest hash function, one should perform the following steps:
- Create a MessageDigest Object that implements the “MD5” algorithm.
- Update the digest with the byte array from a given String, using the
update(byte[] input)API method. - Complete the hash computation, using the
digestAPI method and return the computated hash value in a byte array. - Invoke the above steps for two different Strings, as shown in the
getDigest(String str)method of the example, and then use theisEqual(byte[] digesta, byte[] digestb)API method to compare the two results, in order to check their consistency.
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core;
import java.security.MessageDigest;
public class Main {
public static void main(String[] args) throws Exception {
String str1 = "javacodegeeks.com";
String str2 = "javacodegeeks";
byte[] fDigest = getDigest(str1);
byte[] sDigest = getDigest(str2);
if (MessageDigest.isEqual(fDigest, sDigest)) {
System.out.println("str1 is equal to str2");
} else {
System.out.println("str1 is NOT equal to str2");
}
}
public static byte[] getDigest(String str) throws Exception {
MessageDigest hash = MessageDigest.getInstance("MD5");
byte[] data = str.getBytes();
hash.update(data);
return hash.digest();
}
}
Output:
str1 is NOT equal to str2
This was an example of how to check message consistency using the MessageDigest hash function in Java.
