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How to Calculate MD 5 in Java

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“MD5” corresponds to a widely used cryptographic algorithm in Java which generates a hash of 128 bits. This algorithm utilizes the “MessageDigest” class which is contained in the “java.security” package. This algorithm is effective as it consumes less resources.

This article will discuss the approach to compute “MD5” in Java.

What is MD5?

“MD5” corresponds to a cryptographic algorithm that gives the hash functions to retrieve a fixed length i.e., 128-bit (16 bytes) hash value. 

How to Calculate MD 5 in Java?

To compute the cryptographic hashing value in Java, the “MessageDigest” class is utilized. This class provides the following cryptographic hash function to return the hash value of a text:

  • MD5 
  • SHA-1 
  • SHA-256 

Working of the “MessageDigest” Class

The above-stated hash functions/algorithms are initialized in the static “getInstance()” method. After opting for the algorithm i.e., “MD5” etc., it computes the digest value and retrieves the results in a byte array. After that, the “BigInteger” class is applied which transforms the resultant byte array into the corresponding sign-magnitude representation. 

Advantages of MD5

  • Convenient for comparing small hashes.
  • Less consumption of resources.
  • Convenience in storing passwords.
  • Improved Integrity.

Working of MD5

The “MD5” algorithm works based on the following 4 steps:

Step 1: Add Extra Bits

The first step of the algorithm includes appending extra bits to the provided string. It is done to make the length of the string a multiple of 512 bits. 

Step 2: Append/Add Length

After adding extra bits, add length by appending 64 bits at last. It keeps track of the input’s length provided by the user.

Step 3: Initialize the MD Buffer

MD buffer refers to a 4-word (A, B, C, D) buffer where each word refers to a 32-bit register that calculates the message digest’s value.

Step 4: Processing in a 16-Word Block

The “MD5” algo utilizes the functions(auxiliary) that take the inputs as three 32-bit numbers and generate 32-bits as an outcome. These functions utilize the OR, XOR, and NOR operators.

Example: Calculating the “MD5” Hash Value in Java

The below code example computes the “MD5” hash value:

import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class MD5 {
public static String retrieveMd5(String x){
  try {
  MessageDigest a = MessageDigest.getInstance("MD5");
  byte[] messageDigest = a.digest(x.getBytes());
  BigInteger b = new BigInteger(1, messageDigest);
  String hashtext = b.toString(16);
  while (hashtext.length() < 32) {
    hashtext = "0" + hashtext;
}
  return hashtext;
}
  catch (NoSuchAlgorithmException except) {
    throw new RuntimeException(except);
}}
public static void main(String args[]) throws NoSuchAlgorithmException{
  String c = "Harry";
  System.out.println("HashCode Generated Via MD5 -> " + retrieveMd5(c));
}}

According to the above code limes, perform the below-given steps:

  • Declare the function “retrieveMd5()” that takes the passed string as its argument.
  • In the “try” block, apply the “getInstance()” method with the “MD5” hashing.
  • After that, the “digest()” method is utilized to compute the message digest of an input digest that retrieves an array of bytes.
  • Now, transform the array to the representation of signum.
  • In the next step, convert the message digest to hex value via the combined “toString()” and “length()” methods.
  • In the “catch” block, cope up with the probable message digest algorithms limitation.
  • Finally, in “main”, invoke the defined function by passing the defined string as its argument to fetch the corresponding hashcode based on this string.

Output

This outcome implies that the corresponding hash code with respect to the string is generated appropriately.

Conclusion

To compute the cryptographic hashing value in Java, the “MessageDigest” class is utilized to compute the digest value, retrieves the results in a byte array and the “BigInteger” class transforms the resultant byte array into its sign-magnitude representation. This write-up elaborated on computing the “MD 5” hash value in Java.