bouncycastle(3)Learn from others DES

bouncycastle(3)Learn from others DES

DES - Data Encryption Standard
The most important parameters are as follow: Key, Data, Mode.
A will create the key, publish the key to B, create the encryption data with key, publish the data to B
B will receive the key and the data, decrypt the data with key.

The most import class is as follow:
package com.sillycat.easycastle.encryption;

import java.security.Key;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

public abstract class DESCoder extends Coder {

     /**
      * ALGORITHM
      * we can change the algorithm to every value as follow,
      * the key size will change according to the algorithm you choose
      * <pre>
      * DES                  key size must be equal to 56
      * DESede(TripleDES)    key size must be equal to 112 or 168
      * AES                  key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
      * Blowfish             key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
      * RC2                  key size must be between 40 and 1024 bits
      * RC4(ARCFOUR)         key size must be between 40 and 1024 bits
      * </pre>
      */
     public static final String ALGORITHM = "DES";

     /**
      * convert to key
      * @param key
      * @return
      * @throws Exception
      */
     private static Key toKey(byte[] key) throws Exception {
          DESKeySpec dks = new DESKeySpec(key);
          SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
          SecretKey secretKey = keyFactory.generateSecret(dks);

          // If we want to use other algorithm as AES,Blowfish, Just use the follow statement
          // SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);

          return secretKey;
     }

     /**
      * decrypt the data
      * @param data
      * @param key
      * @return
      * @throws Exception
      */
     public static byte[] decrypt(byte[] data, String key) throws Exception {
          Key k = toKey(decryptBASE64(key));

          Cipher cipher = Cipher.getInstance(ALGORITHM);
          cipher.init(Cipher.DECRYPT_MODE, k);

          return cipher.doFinal(data);
     }

     /**
      * encrypt
      *
      * @param data
      * @param key
      * @return
      * @throws Exception
      */
     public static byte[] encrypt(byte[] data, String key) throws Exception {
          Key k = toKey(decryptBASE64(key));
          Cipher cipher = Cipher.getInstance(ALGORITHM);
          cipher.init(Cipher.ENCRYPT_MODE, k);

          return cipher.doFinal(data);
     }

     /**
      * generate the key
      *
      * @return
      * @throws Exception
      */
     public static String initKey() throws Exception {
          return initKey(null);
     }

     /**
      * generate the key
      *
      * @param seed
      * @return
      * @throws Exception
      */
     public static String initKey(String seed) throws Exception {
          SecureRandom secureRandom = null;

          if (seed != null) {
               secureRandom = new SecureRandom(decryptBASE64(seed));
          } else {
               secureRandom = new SecureRandom();
          } 
        

          KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM);
          kg.init(secureRandom);

          SecretKey secretKey = kg.generateKey();

          return encryptBASE64(secretKey.getEncoded());
     }

}


And the test class is as follow:
package com.sillycat.easycastle.encryption;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class DESCoderTest {

     @Test
     public void test() throws Exception {
          String inputStr = "DES";
          String key = DESCoder.initKey();
          System.out.println("original:\t" + inputStr);

          System.out.println("key:\t" + key);
 
          byte[] inputData = inputStr.getBytes();
          inputData = DESCoder.encrypt(inputData, key);
        System.out.println("encryption data:\t" + inputData);
          System.out.println("encryption data(base64+des):\t" + DESCoder.encryptBASE64(inputData));

          byte[] outputData = DESCoder.decrypt(inputData, key);
          String outputStr = new String(outputData);

          System.out.println("decryption data:\t" + outputStr);

          assertEquals(inputStr, outputStr);
     }

}


This project is host by github and project name is easycastle.


references:
http://snowolf.iteye.com/blog/380034