Java Tutorial/Security/DES Data Encryption Standard

Basic symmetric encryption example with CTR using DES

   <source lang="java">

import java.security.Security; import javax.crypto.Cipher; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.SecretKeySpec; public class MainClass {

 public static void main(String[] args) throws Exception {
   Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
   byte[] input = "input".getBytes();
   byte[] keyBytes = "12345678".getBytes();
   byte[] ivBytes = "input123".getBytes();
   SecretKeySpec key = new SecretKeySpec(keyBytes, "DES");
   IvParameterSpec ivSpec = new IvParameterSpec(ivBytes);
   Cipher cipher = Cipher.getInstance("DES/CTR/NoPadding", "BC");
   cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
   byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
   int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
   ctLength += cipher.doFinal(cipherText, ctLength);
   System.out.println("cipher: " + new String(cipherText));
   cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);
   byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
   int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);
   ptLength += cipher.doFinal(plainText, ptLength);
   System.out.println("plain : " + new String(plainText));
 }

}</source>

CBC using DES with an IV based on a nonce. In this case a hypothetical message number.

   <source lang="java">

import java.security.Security; import javax.crypto.Cipher; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.SecretKeySpec; public class MainClass {

 public static void main(String[] args) throws Exception {
   Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
   byte[] input = "input".getBytes();
   byte[] keyBytes = "input123".getBytes();
   byte[] msgNumber = "input".getBytes();
   IvParameterSpec zeroIv = new IvParameterSpec(new byte[8]);
   SecretKeySpec key = new SecretKeySpec(keyBytes, "DES");
   Cipher cipher = Cipher.getInstance("DES/CBC/PKCS7Padding", "BC");
   cipher.init(Cipher.ENCRYPT_MODE, key, zeroIv);
   IvParameterSpec encryptionIv = new IvParameterSpec(cipher.doFinal(msgNumber), 0, 8);
   cipher.init(Cipher.ENCRYPT_MODE, key, encryptionIv);
   byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
   int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
   ctLength += cipher.doFinal(cipherText, ctLength);
   System.out.println("cipher: " + new String(cipherText) + " bytes: " + ctLength);
   cipher.init(Cipher.ENCRYPT_MODE, key, zeroIv);
   IvParameterSpec decryptionIv = new IvParameterSpec(cipher.doFinal(msgNumber), 0, 8);
   cipher.init(Cipher.DECRYPT_MODE, key, decryptionIv);
   byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
   int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);
   ptLength += cipher.doFinal(plainText, ptLength);
   System.out.println("plain : " + new String(plainText, ptLength));
 }

}</source>

Decrypt an object with DES

   <source lang="java">

import java.io.File; import java.io.FileInputStream; import java.io.ObjectInputStream; import javax.crypto.Cipher; import javax.crypto.SealedObject; import javax.crypto.SecretKey; public class Main {

 private static Object readFromFile(String filename) throws Exception {
   ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File(filename)));
   Object object = ois.readObject();
   ois.close();
   return object;
 }
 public static void main(String[] args) throws Exception {
   SecretKey key = (SecretKey) readFromFile("secretkey.dat");
   SealedObject sealedObject = (SealedObject) readFromFile("sealed.dat");
   String algorithmName = sealedObject.getAlgorithm();
   Cipher cipher = Cipher.getInstance(algorithmName);
   cipher.init(Cipher.DECRYPT_MODE, key);
   String text = (String) sealedObject.getObject(cipher);
   System.out.println("Text = " + text);
 }

}</source>

Encrypt an object with DES

   <source lang="java">

import java.io.File; import java.io.FileOutputStream; import java.io.ObjectOutputStream; import javax.crypto.Cipher; import javax.crypto.KeyGenerator; import javax.crypto.SealedObject; import javax.crypto.SecretKey; public class Main {

 private static void writeToFile(String filename, Object object) throws Exception {
  ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File(filename)));
   oos.writeObject(object);
   oos.flush();
   oos.close();
 }
 public static void main(String[] args) throws Exception {
   SecretKey key = KeyGenerator.getInstance("DES").generateKey();
   writeToFile("secretkey.dat", key);
   Cipher cipher = Cipher.getInstance("DES");
   cipher.init(Cipher.ENCRYPT_MODE, key);
   SealedObject sealedObject = new SealedObject("THIS IS A SECRET MESSAGE!", cipher);
   writeToFile("sealed.dat", sealedObject);
 }

}</source>

Encrypting a File or Stream with DES

   <source lang="java">

import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.InputStream; import java.io.OutputStream; import java.security.spec.AlgorithmParameterSpec; import javax.crypto.Cipher; import javax.crypto.CipherInputStream; import javax.crypto.CipherOutputStream; import javax.crypto.KeyGenerator; import javax.crypto.SecretKey; import javax.crypto.spec.IvParameterSpec; class DesEncrypter {

 byte[] buf = new byte[1024];
 Cipher ecipher;
 Cipher dcipher;
 DesEncrypter(SecretKey key) throws Exception{
   byte[] iv = new byte[] { (byte) 0x8E, 0x12, 0x39, (byte) 0x9C, 0x07, 0x72, 0x6F, 0x5A };
   AlgorithmParameterSpec paramSpec = new IvParameterSpec(iv);
   ecipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
   dcipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
   ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
   dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
 }

 public void encrypt(InputStream in, OutputStream out)  throws Exception{
   out = new CipherOutputStream(out, ecipher);
   int numRead = 0;
   while ((numRead = in.read(buf)) >= 0) {
     out.write(buf, 0, numRead);
   }
   out.close();
 }
 public void decrypt(InputStream in, OutputStream out)  throws Exception{
   in = new CipherInputStream(in, dcipher);
   int numRead = 0;
   while ((numRead = in.read(buf)) >= 0) {
     out.write(buf, 0, numRead);
   }
   out.close();
 }

} public class Main {

 public static void main(String[] argv) throws Exception {
   SecretKey key = KeyGenerator.getInstance("DES").generateKey();
   DesEncrypter encrypter = new DesEncrypter(key);
   encrypter.encrypt(new FileInputStream("cleartext1"), new FileOutputStream("ciphertext"));
   encrypter.decrypt(new FileInputStream("ciphertext"), new FileOutputStream("cleartext2"));
 }

}</source>

Encrypting a String with DES

   <source lang="java">

import javax.crypto.Cipher; import javax.crypto.KeyGenerator; import javax.crypto.SecretKey; class DesEncrypter {

 Cipher ecipher;
 Cipher dcipher;
 DesEncrypter(SecretKey key) throws Exception {
   ecipher = Cipher.getInstance("DES");
   dcipher = Cipher.getInstance("DES");
   ecipher.init(Cipher.ENCRYPT_MODE, key);
   dcipher.init(Cipher.DECRYPT_MODE, key);
 }
 public String encrypt(String str) throws Exception {
   // Encode the string into bytes using utf-8
   byte[] utf8 = str.getBytes("UTF8");
   // Encrypt
   byte[] enc = ecipher.doFinal(utf8);
   // Encode bytes to base64 to get a string
   return new sun.misc.BASE64Encoder().encode(enc);
 }
 public String decrypt(String str) throws Exception {
   // Decode base64 to get bytes
   byte[] dec = new sun.misc.BASE64Decoder().decodeBuffer(str);
   byte[] utf8 = dcipher.doFinal(dec);
   // Decode using utf-8
   return new String(utf8, "UTF8");
 }

} public class Main {

 public static void main(String[] argv) throws Exception {
   SecretKey key = KeyGenerator.getInstance("DES").generateKey();
   DesEncrypter encrypter = new DesEncrypter(key);
   String encrypted = encrypter.encrypt("Don"t tell anybody!");
   String decrypted = encrypter.decrypt(encrypted);
 }

}</source>

Encrypting with DES Using a Pass Phrase

   <source lang="java">

import java.security.spec.AlgorithmParameterSpec; import java.security.spec.KeySpec; import javax.crypto.Cipher; import javax.crypto.SecretKey; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.PBEKeySpec; import javax.crypto.spec.PBEParameterSpec; import sun.misc.BASE64Decoder; import sun.misc.BASE64Encoder; class DesEncrypter {

 Cipher ecipher;
 Cipher dcipher;
 byte[] salt = { (byte) 0xA9, (byte) 0x9B, (byte) 0xC8, (byte) 0x32, (byte) 0x56, (byte) 0x35,
     (byte) 0xE3, (byte) 0x03 };
 DesEncrypter(String passPhrase) throws Exception {
   int iterationCount = 2;
   KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt, iterationCount);
   SecretKey key = SecretKeyFactory.getInstance("PBEWithMD5AndDES").generateSecret(keySpec);
   ecipher = Cipher.getInstance(key.getAlgorithm());
   dcipher = Cipher.getInstance(key.getAlgorithm());
   AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt, iterationCount);
   ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
   dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
 }
 public String encrypt(String str) throws Exception {
   return new BASE64Encoder().encode(ecipher.doFinal(str.getBytes()));
 }
 public String decrypt(String str) throws Exception {
   return new String(dcipher.doFinal(new BASE64Decoder().decodeBuffer(str)));
 }

} public class Main {

 public static void main(String[] argv) throws Exception {
   DesEncrypter encrypter = new DesEncrypter("My Pass Phrase!");
   String encrypted = encrypter.encrypt("Don"t tell anybody!");
   String decrypted = encrypter.decrypt(encrypted);
 }

}</source>

Message without tampering with MAC (DES), encryption AES in CTR mode

   <source lang="java">

import java.security.Key; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.SecureRandom; import java.security.Security; import javax.crypto.Cipher; import javax.crypto.KeyGenerator; import javax.crypto.Mac; import javax.crypto.SecretKey; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.SecretKeySpec; public class MainClass {

 public static void main(String[] args) throws Exception {
   Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
   SecureRandom random = new SecureRandom();
   IvParameterSpec ivSpec = createCtrIvForAES();
   Key key = createKeyForAES(256, random);
   Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding", "BC");
   String input = "12345678";
   Mac mac = Mac.getInstance("DES", "BC");
   byte[] macKeyBytes = new byte[] { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };
   Key macKey = new SecretKeySpec(macKeyBytes, "DES");
   cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
   byte[] cipherText = new byte[cipher.getOutputSize(input.length() + mac.getMacLength())];
   int ctLength = cipher.update(input.getBytes(), 0, input.length(), cipherText, 0);
   mac.init(macKey);
   mac.update(input.getBytes());
   ctLength += cipher.doFinal(mac.doFinal(), 0, mac.getMacLength(), cipherText, ctLength);
   cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);
   byte[] plainText = cipher.doFinal(cipherText, 0, ctLength);
   int messageLength = plainText.length - mac.getMacLength();
   mac.init(macKey);
   mac.update(plainText, 0, messageLength);
   byte[] messageHash = new byte[mac.getMacLength()];
   System.arraycopy(plainText, messageLength, messageHash, 0, messageHash.length);
   System.out.println("plain : " + new String(plainText) + " verified: "
       + MessageDigest.isEqual(mac.doFinal(), messageHash));
 }
 public static SecretKey createKeyForAES(int bitLength, SecureRandom random)
     throws NoSuchAlgorithmException, NoSuchProviderException {
   KeyGenerator generator = KeyGenerator.getInstance("AES", "BC");
   generator.init(128, random);
   return generator.generateKey();
 }
 public static IvParameterSpec createCtrIvForAES() {
   return new IvParameterSpec("1234567812345678".getBytes());
 }

}</source>