Java Tutorial/Security/Password Based Encryption

PBE File Encrypt

   <source lang="java">

import java.io.BufferedOutputStream; import java.io.FileInputStream; import java.io.FileOutputStream; import java.security.MessageDigest; import javax.crypto.Cipher; import javax.crypto.CipherInputStream; import javax.crypto.SecretKey; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.PBEKeySpec; import javax.crypto.spec.PBEParameterSpec; public class MainClass {

 public static void main(String[] args) throws Exception{
   Cipher cipher = createCipher(Cipher.ENCRYPT_MODE);
   applyCipher("file_to_encrypt", "encrypted_file", cipher);
   cipher = createCipher(Cipher.DECRYPT_MODE);
   applyCipher("file_to_decrypt", "decrypted_file", cipher);
 }
 static Cipher createCipher(int mode) throws Exception {
   PBEKeySpec keySpec = new PBEKeySpec("test".toCharArray());
   SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
   SecretKey key = keyFactory.generateSecret(keySpec);
   MessageDigest md = MessageDigest.getInstance("MD5");
   md.update("input".getBytes());
   byte[] digest = md.digest();
   byte[] salt = new byte[8];
   for (int i = 0; i < 8; ++i)
     salt[i] = digest[i];
   PBEParameterSpec paramSpec = new PBEParameterSpec(salt, 20);
   Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");
   cipher.init(mode, key, paramSpec);
   return cipher;
 }
 static void applyCipher(String inFile, String outFile, Cipher cipher) throws Exception {
   CipherInputStream in = new CipherInputStream(new FileInputStream(inFile), cipher);
   BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(outFile));
   int BUFFER_SIZE = 8;
   byte[] buffer = new byte[BUFFER_SIZE];
   int numRead = 0;
   do {
     numRead = in.read(buffer);
     if (numRead > 0)
       out.write(buffer, 0, numRead);
   } while (numRead == 8);
 }

}</source>

PBE With SHA And Two fish

   <source lang="java">

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; public class MainClass {

 public static void main(String[] args) throws Exception {
   System.out.println(decrypt(new char[] { "a", "b", "c", "d" }, "plaintext1234567890"));
 }
 private static String decrypt(char[] password, String text) throws Exception {
   String salt = text.substring(0, 12);
   String ciphertext = text.substring(12, text.length());
   BASE64Decoder decoder = new BASE64Decoder();
   byte[] saltArray = decoder.decodeBuffer(salt);
   byte[] ciphertextArray = decoder.decodeBuffer(ciphertext);
   PBEKeySpec keySpec = new PBEKeySpec(password);
   SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithSHAAndTwofish-CBC");
   SecretKey key = keyFactory.generateSecret(keySpec);
   PBEParameterSpec paramSpec = new PBEParameterSpec(saltArray, 1000);
   Cipher cipher = Cipher.getInstance("PBEWithSHAAndTwofish-CBC");
   cipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
   return new String(cipher.doFinal(ciphertextArray));
 }

}</source>

Read the first 8 bytes of the ciphertext and use that as the salt

   <source lang="java">

import java.util.Random; 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.BASE64Encoder; public class MainClass {

 public static void main(String[] args) throws Exception {
  System.out.println(encrypt(new char[] { "a", "b", "c", "d" }, "plaintext1234567890"));
 }
 private static String encrypt(char[] password, String plaintext) throws Exception {
   byte[] salt = new byte[8];
   Random random = new Random();
   random.nextBytes(salt);
   PBEKeySpec keySpec = new PBEKeySpec(password);
   SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithSHAAndTwofish-CBC");
   SecretKey key = keyFactory.generateSecret(keySpec);
   PBEParameterSpec paramSpec = new PBEParameterSpec(salt, 1000);
   Cipher cipher = Cipher.getInstance("PBEWithSHAAndTwofish-CBC");
   cipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
   byte[] ciphertext = cipher.doFinal(plaintext.getBytes());
   BASE64Encoder encoder = new BASE64Encoder();
   String saltString = encoder.encode(salt);
   String ciphertextString = encoder.encode(ciphertext);
   return saltString + ciphertextString;
 }

}</source>