Java Tutorial/Security/DES Data Encryption Standard

Basic symmetric encryption example with CTR using DES

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));
  }
}

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

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));
  }
}

Decrypt an object with DES

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);
  }
}

Encrypt an object with DES

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);
  }
}

Encrypting a File or Stream with DES

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"));
  }
}

Encrypting a String with DES

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);
  }
}

Encrypting with DES Using a Pass Phrase

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);
  }
}

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

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());
  }
}