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DES Algorithm - Java Implementation

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(Continued from previous part...)

Test Cases of DES Encryption and Decryption

Once I got my DES implementation working, I created the following testing Java program to performed several test cases so that I can validate the results with other DES implementations:

/* CipherDesTest.java
 * Copyright (c) 2002 by Dr. Herong Yang, http://www.herongyang.com/
 */
import java.io.*;
import herong.CipherDES;
class CipherDesTest {
   public static void main(String[] a) {
      if (a.length<1) {
         System.out.println("Usage:");
         System.out.println("java CipherDesTest 1");
         return;
      }
      String test = a[0];
      try {
         byte[] theKey = null;
         byte[] theMsg = null; 
         byte[] theExp = null; 
         if (test.equals("1")) { 
            theKey = hexToBytes("133457799BBCDFF1");
            theMsg = hexToBytes("0123456789ABCDEF");
            theExp = hexToBytes("85E813540F0AB405");
         } else if (test.equals("2")) { 
            theKey = hexToBytes("38627974656B6579"); // "8bytekey"
            theMsg = hexToBytes("6D6573736167652E"); // "message."
            theExp = hexToBytes("7CF45E129445D451");
         } else {
            System.out.println("Usage:");
            System.out.println("java CipherDesTest 1");
            return;
         }	
         byte[][] subKeys = CipherDES.getSubkeys(theKey);
         byte[] theCph = CipherDES.cipher(theMsg,subKeys,"encrypt");
         System.out.println("Key     : "+bytesToHex(theKey));
         System.out.println("Message : "+bytesToHex(theMsg));
         System.out.println("Cipher  : "+bytesToHex(theCph));
         System.out.println("Expected: "+bytesToHex(theExp));
      } catch (Exception e) {
         e.printStackTrace();
         return;
      }
   }
   public static byte[] hexToBytes(String str) {
      if (str==null) {
         return null;
      } else if (str.length() < 2) {
         return null;
      } else {
         int len = str.length() / 2;
         byte[] buffer = new byte[len];
         for (int i=0; i<len; i++) {
             buffer[i] = (byte) Integer.parseInt(
                str.substring(i*2,i*2+2),16);
         }
         return buffer;
      }

   }
   public static String bytesToHex(byte[] data) {
      if (data==null) {
         return null;
      } else {
         int len = data.length;
         String str = "";
         for (int i=0; i<len; i++) {
            if ((data[i]&0xFF)<16) str = str + "0" 
               + java.lang.Integer.toHexString(data[i]&0xFF);
            else str = str
               + java.lang.Integer.toHexString(data[i]&0xFF);
         }
         return str.toUpperCase();
      }
   }            
}

Note that this program, CipherDesTest.java, can be easily modified to add other testing cases. To run CipherDesTest.java, you need compile CipherDES.java into a package called "herong", and run them together.

Case 1 - Taken from The DES Algorithm Illustrated:

java -cp . CipherDesTest 1

Key     : 133457799BBCDFF1
Message : 0123456789ABCDEF
Cipher  : 85E813540F0AB405
Expected: 85E813540F0AB405

Case 2 - Modified from DES Source Code:

java -cp . CipherDesTest 2

Key     : 38627974656B6579
Message : 6D6573736167652E
Cipher  : 7CF45E129445D451
Expected: 7CF45E129445D451

Exercise: Improve this program to handle multiple input blocks.

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