Java MD5 Hashing Example

The MD5, defined in RFC 1321, is a hash algorithm to turn inputs into a fixed 128-bit (16 bytes) length of the hash value.

Note

MD5 is not collision-resistant – Two different inputs may producing the same hash value. Read this MD5 vulnerabilities. There are many fast and secure hashing algorithms like SHA3-256 or BLAKE2; For password hashing, we can use Bcrypt or Argon2. If possible, do not use MD5 in any security-related cryptography tasks.

In Java, we can use MessageDigest to generate the MD5 algorithm.

  MessageDigest md = MessageDigest.getInstance("MD5");
  byte[] result = md.digest(input);

1. Java MD5 Hashing

This Java example uses MD5 to produce a hash value from a String.

MD5Utils.java

package com.favtuts.crypto.hash;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Utils {

    private static final Charset UTF_8 = StandardCharsets.UTF_8;
    private static final String OUTPUT_FORMAT = "%-20s:%s";

    private static byte[] digest(byte[] input) {
        MessageDigest md;
        try {
            md = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalArgumentException(e);
        }

        byte[] result = md.digest(input);
        return result;
    }

    private static String bytesToHex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (byte b : bytes) {
            sb.append(String.format("%02x", b));
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        String pText = "Hello MD5";
        System.out.println(String.format(OUTPUT_FORMAT, "Input (string)", pText));
        System.out.println(String.format(OUTPUT_FORMAT, "Input (length)", pText.length()));

        byte[] md5InBytes = MD5Utils.digest(pText.getBytes(UTF_8));
        System.out.println(String.format(OUTPUT_FORMAT, "MD5 (hex) ", bytesToHex(md5InBytes)));
        // fixed length, 16 bytes, 128 bits.
        System.out.println(String.format(OUTPUT_FORMAT, "MD5 (length)", md5InBytes.length));
    }
}

Output

Input (string)      :Hello MD5
Input (length)      :9
MD5 (hex)           :e5dadf6524624f79c3127e247f04b548
MD5 (length)        :16

2. Java MD5 File Checksum.

For the file checksum, the ideas are the same, but we need some extra IO classes to handle the input stream.

Here is a text file.

c:\\test\\readme.txt

Hello MD5

This Java program will generate an MD5 file checksum from a file.

MD5Utils.java

package com.favtuts.crypto.hash;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Utils {

    private static final Charset UTF_8 = StandardCharsets.UTF_8;
    private static final String OUTPUT_FORMAT = "%-20s:%s";

    private static byte[] checksum(String filePath) {

        MessageDigest md;
        try {
            md = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalArgumentException(e);
        }

        try (InputStream is = new FileInputStream(filePath);
             DigestInputStream dis = new DigestInputStream(is, md)) {
            while (dis.read() != -1) ; //empty loop to clear the data
            md = dis.getMessageDigest();
        } catch (IOException e) {
            throw new IllegalArgumentException(e);
        }
        return md.digest();

    }

    private static String bytesToHex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (byte b : bytes) {
            sb.append(String.format("%02x", b));
        }
        return sb.toString();
    }

    public static void main(String[] args) {

        String file = "c:\\test\\readme.txt";
        System.out.println(String.format(OUTPUT_FORMAT, "Input (file) ", file));
        System.out.println(String.format(OUTPUT_FORMAT, "MD5 (checksum hex) ", bytesToHex(checksum(file))));

    }

}

Output

Input (file)        :c:\test\readme.txt
MD5 (checksum hex)  :e5dadf6524624f79c3127e247f04b548

3. Apache Commons Codec

This example uses the commons-codec library to generate the MD5 hash value.

pom.xml

  <dependency>
      <groupId>commons-codec</groupId>
      <artifactId>commons-codec</artifactId>
      <version>1.14</version>
  </dependency>

3.1 MD5 hash value from a String.

import org.apache.commons.codec.digest.DigestUtils;

    String pText = "Hello MD5";
    System.out.println(DigestUtils.md5Hex(password));

Output

e5dadf6524624f79c3127e247f04b548

3.2 MD5 hash value from a File.

  try (InputStream is = new FileInputStream("c:\\test\\readme.txt")) {
      String checksum = DigestUtils.md5Hex(is);
      System.out.println(checksum);
  } catch (IOException e) {
      e.printStackTrace();
  }

Output

e5dadf6524624f79c3127e247f04b548

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-crypto

References

• MessageDigest JavaDoc
• Apache Commons Codec
• Java – How to convert byte array to Hex
• MD5
• RFC 1321