Cryptography Tutorials - Herong's Tutorial Notes
Dr. Herong Yang, Version 4.00
 This site Web DES Algorithm - Java Implementation Part:   1  2  3  4  This tutorial help you to understand: A simple Java implementation of the DES cipher algorithm. Multiple test cases of DES encryption and decryption. CipherDES.java - A Simple Java Implementation of DES Merging the illustration programs from the previous chapter together, I got the following simple Java implementation of the DES algorithm, CipherDES.java: ```/* CipherDES.java * Copyright (c) 2002 by Dr. Herong Yang, http://www.herongyang.com/ */ package herong; import java.io.*; public class CipherDES { public static void main(String[] a) { if (a.length<4) { System.out.println("Usage:"); System.out.println("java DesCipher encrypt/decrypt keyFile" +" msgFile cphFile"); return; } String mode = a[0]; String keyFile = a[1]; String msgFile = a[2]; String cphFile = a[3]; try { byte[] theKey = readBytes(keyFile); byte[][] subKeys = getSubkeys(theKey); byte[] theMsg = readBytes(msgFile); byte[] theCph = cipher(theMsg,subKeys,mode); writeBytes(theCph,cphFile); printBytes(theKey,"Key block"); printBytes(theMsg,"Input block"); printBytes(theCph,"Output block"); } catch (Exception e) { e.printStackTrace(); return; } } static final int[] IP = { 58, 50, 42, 34, 26, 18, 10, 2, 60, 52, 44, 36, 28, 20, 12, 4, 62, 54, 46, 38, 30, 22, 14, 6, 64, 56, 48, 40, 32, 24, 16, 8, 57, 49, 41, 33, 25, 17, 9, 1, 59, 51, 43, 35, 27, 19, 11, 3, 61, 53, 45, 37, 29, 21, 13, 5, 63, 55, 47, 39, 31, 23, 15, 7 }; static final int[] E = { 32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8, 9, 10, 11, 12, 13, 12, 13, 14, 15, 16, 17, 16, 17, 18, 19, 20, 21, 20, 21, 22, 23, 24, 25, 24, 25, 26, 27, 28, 29, 28, 29, 30, 31, 32, 1 }; static final int[] P = { 16, 7, 20, 21, 29, 12, 28, 17, 1, 15, 23, 26, 5, 18, 31, 10, 2, 8, 24, 14, 32, 27, 3, 9, 19, 13, 30, 6, 22, 11, 4, 25 }; static final int[] INVP = { 40, 8, 48, 16, 56, 24, 64, 32, 39, 7, 47, 15, 55, 23, 63, 31, 38, 6, 46, 14, 54, 22, 62, 30, 37, 5, 45, 13, 53, 21, 61, 29, 36, 4, 44, 12, 52, 20, 60, 28, 35, 3, 43, 11, 51, 19, 59, 27, 34, 2, 42, 10, 50, 18, 58, 26, 33, 1, 41, 9, 49, 17, 57, 25 }; public static byte[] cipher(byte[] theMsg, byte[][] subKeys, String mode) throws Exception { if (theMsg.length<8) throw new Exception("Message is less than 64 bits."); theMsg = selectBits(theMsg,IP); // Initial Permutation int blockSize = IP.length; byte[] l = selectBits(theMsg,0,blockSize/2); byte[] r = selectBits(theMsg,blockSize/2,blockSize/2); int numOfSubKeys = subKeys.length; for (int k=0; k

Dr. Herong Yang, updated in 2007
Cryptography Tutorials - Herong's Tutorial Notes - DES Algorithm - Java Implementation