Cryptography Tutorials - Herong's Tutorial Examples - v5.42, by Herong Yang
DESSubkeysTest.java - DES Key Schedule Algorithm Illustration
This section provides a tutorial Java program, DESSubkeysTest.java, to illustrate how DES key schedule algorithm works.
As an illustration to the DES key schedule algorithm described in the previous chapter, I wrote the following Java program, DESKSubkeysTest.java:
/* DESSubkeysTest.java * Copyright (c) HerongYang.com. All Rights Reserved. */ class DESSubkeysTest { public static void main(String[] a) { try { byte[] theKey = getTestKey(); byte[][] subKeys = getSubkeys(theKey); boolean ok = validateSubkeys(subKeys); System.out.println("DES subkeys test result: "+ok); } catch (Exception e) { e.printStackTrace(); } } static final int[] PC1 = { 57, 49, 41, 33, 25, 17, 9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51, 43, 35, 27, 19, 11, 3, 60, 52, 44, 36, 63, 55, 47, 39, 31, 23, 15, 7, 62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21, 13, 5, 28, 20, 12, 4 }; static final int[] PC2 = { 14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21, 10, 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13, 2, 41, 52, 31, 37, 47, 55, 30, 40, 51, 45, 33, 48, 44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29, 32 }; static final int[] SHIFTS = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 }; private static byte[][] getSubkeys(byte[] theKey) throws Exception { printBytes(theKey,"Input key"); int activeKeySize = PC1.length; int numOfSubKeys = SHIFTS.length; byte[] activeKey = selectBits(theKey,PC1); printBytes(activeKey,"After permuted choice 1 - Active key"); int halfKeySize = activeKeySize/2; byte[] c = selectBits(activeKey,0,halfKeySize); byte[] d = selectBits(activeKey,halfKeySize,halfKeySize); byte[][] subKeys = new byte[numOfSubKeys][]; for (int k=0; k<numOfSubKeys; k++) { c = rotateLeft(c,halfKeySize,SHIFTS[k]); d = rotateLeft(d,halfKeySize,SHIFTS[k]); byte[] cd = concatenateBits(c,halfKeySize,d,halfKeySize); printBytes(cd,"Subkey #"+(k+1)+" after shifting"); subKeys[k] = selectBits(cd,PC2); printBytes(subKeys[k],"Subkey #"+(k+1) +" after permuted choice 2"); } return subKeys; } private static byte[] rotateLeft(byte[] in, int len, int step) { int numOfBytes = (len-1)/8 + 1; byte[] out = new byte[numOfBytes]; for (int i=0; i<len; i++) { int val = getBit(in,(i+step)%len); setBit(out,i,val); } return out; }
private static byte[] concatenateBits(byte[] a, int aLen, byte[] b, int bLen) { int numOfBytes = (aLen+bLen-1)/8 + 1; byte[] out = new byte[numOfBytes]; int j = 0; for (int i=0; i<aLen; i++) { int val = getBit(a,i); setBit(out,j,val); j++; } for (int i=0; i<bLen; i++) { int val = getBit(b,i); setBit(out,j,val); j++; } return out; } private static byte[] selectBits(byte[] in, int pos, int len) { int numOfBytes = (len-1)/8 + 1; byte[] out = new byte[numOfBytes]; for (int i=0; i<len; i++) { int val = getBit(in,pos+i); setBit(out,i,val); } return out; } private static byte[] selectBits(byte[] in, int[] map) { int numOfBytes = (map.length-1)/8 + 1; byte[] out = new byte[numOfBytes]; for (int i=0; i<map.length; i++) { int val = getBit(in,map[i]-1); setBit(out,i,val); // System.out.println("i="+i+", pos="+(map[i]-1)+", val="+val); } return out; } private static int getBit(byte[] data, int pos) { int posByte = pos/8; int posBit = pos%8; byte valByte = data[posByte]; int valInt = valByte>>(8-(posBit+1)) & 0x0001; return valInt; } private static void setBit(byte[] data, int pos, int val) { int posByte = pos/8; int posBit = pos%8; byte oldByte = data[posByte]; oldByte = (byte) (((0xFF7F>>posBit) & oldByte) & 0x00FF); byte newByte = (byte) ((val<<(8-(posBit+1))) | oldByte); data[posByte] = newByte; } private static void printBytes(byte[] data, String name) { System.out.println(""); System.out.println(name+":"); for (int i=0; i<data.length; i++) { System.out.print(byteToBits(data[i])+" "); } System.out.println(); } private static String byteToBits(byte b) { StringBuffer buf = new StringBuffer(); for (int i=0; i<8; i++) buf.append((int)(b>>(8-(i+1)) & 0x0001)); return buf.toString(); } private static byte[] getTestKey() { String strKey = " 00010011 00110100 01010111 01111001" +" 10011011 10111100 11011111 11110001"; byte[] theKey = new byte[8]; for (int i=0; i<8; i++) { String strByte = strKey.substring(9*i+1,9*i+1+8); theKey[i] = (byte) Integer.parseInt(strByte,2); } return theKey; }
private static boolean validateSubkeys(byte[][] subKeys) { boolean ok = true; String[] strKeys = { " 00011011 00000010 11101111 11111100 01110000 01110010",//1 " 01111001 10101110 11011001 11011011 11001001 11100101",//2 " 01010101 11111100 10001010 01000010 11001111 10011001",//3 " 01110010 10101101 11010110 11011011 00110101 00011101",//4 " 01111100 11101100 00000111 11101011 01010011 10101000",//5 " 01100011 10100101 00111110 01010000 01111011 00101111",//6 " 11101100 10000100 10110111 11110110 00011000 10111100",//7 " 11110111 10001010 00111010 11000001 00111011 11111011",//8 " 11100000 11011011 11101011 11101101 11100111 10000001",//9 " 10110001 11110011 01000111 10111010 01000110 01001111",//0 " 00100001 01011111 11010011 11011110 11010011 10000110",//1 " 01110101 01110001 11110101 10010100 01100111 11101001",//2 " 10010111 11000101 11010001 11111010 10111010 01000001",//3 " 01011111 01000011 10110111 11110010 11100111 00111010",//4 " 10111111 10010001 10001101 00111101 00111111 00001010",//5 " 11001011 00111101 10001011 00001110 00010111 11110101"}; for (int k=0; k<16; k++) { for (int i=0; i<6; i++) { String strByte = strKeys[k].substring(9*i+1,9*i+1+8); byte keyByte = (byte) Integer.parseInt(strByte,2); if (keyByte!=subKeys[k][i]) ok = false; } } return ok; } }
In this program, the input key is hard coded to the same value used by J. Orlin Grabbe in "The DES Algorithm Illustrated". The subkeys generated by the algorithm are validated with those mentioned by J. Orlin Grabbe.
See the next section for the execution output of this tutorial program.
Table of Contents
Introduction to AES (Advanced Encryption Standard)
►DES Algorithm - Illustrated with Java Programs
►DESSubkeysTest.java - DES Key Schedule Algorithm Illustration
DES Key Schedule Algorithm Illustration Program Output
DESCipherTest.java - DES Cipher Algorithm Illustration
DES Cipher Algorithm Illustration Program Output
DES Algorithm Java Implementation
DES Algorithm - Java Implementation in JDK JCE
DES Encryption Operation Modes
PHP Implementation of DES - mcrypt
Blowfish - 8-Byte Block Cipher
Secret Key Generation and Management
Cipher - Secret Key Encryption and Decryption
RSA Implementation using java.math.BigInteger Class
Introduction of DSA (Digital Signature Algorithm)
Java Default Implementation of DSA
Private key and Public Key Pair Generation
PKCS#8/X.509 Private/Public Encoding Standards
Cipher - Public Key Encryption and Decryption
OpenSSL Introduction and Installation
OpenSSL Generating and Managing RSA Keys
OpenSSL Generating and Signing CSR
OpenSSL Validating Certificate Path
"keytool" and "keystore" from JDK
"OpenSSL" Signing CSR Generated by "keytool"
Migrating Keys from "keystore" to "OpenSSL" Key Files
Certificate X.509 Standard and DER/PEM Formats
Migrating Keys from "OpenSSL" Key Files to "keystore"