DES.java
public class DES { /* Initial Permutation */ 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 }; /* Inverse Initial Permutation */ static final int[] IIP = { 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 }; /* Expansion Permutation */ 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 }; /* Permutation Function */ 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 }; /* S-Boxes*/ static final int[] S1 = { 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7, 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8, 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0, 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 }; static final int[] S2 = { 15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10, 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5, 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15, 13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 }; static final int[] S3 = { 10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8, 13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1, 13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7, 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 }; static final int[] S4 = { 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15, 13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9, 10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4, 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 }; static final int[] S5 = { 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9, 14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6, 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14, 11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 }; static final int[] S6 = { 12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11, 10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8, 9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6, 4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 }; static final int[] S7 = { 4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1, 13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6, 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2, 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12 }; static final int[] S8 = { 13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7, 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2, 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8, 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11 }; /* Permuted Choice One */ 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 }; /* Permuted Choice Two */ 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 }; /* Schedule of Left Shifts */ static final int[] SHIFTS = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 }; public DES() { } private byte[] performXOR(byte[] one, byte[] two) { byte[] result = new byte[one.length]; for (int i = 0 ; i < one.length ; i++) { result[i] = (byte) (one[i] ^ two[i]); } return result; } private byte[] permute(byte[] input, int[] mapping) { int byteCount = 1 + (mapping.length - 1) / 8; byte[] output = new byte[byteCount]; int pos; for (int i = 0 ; i < mapping.length ; i++) { pos = mapping[i] - 1; int value = getBitFromArray(input, pos); setBitInArray(output, i, value); } return output; } private int getBitFromArray(byte[] array, int pos) { int value; int bytePos = pos / 8; int bitPos = pos % 8; value = (array[bytePos] >> (8 - (bitPos + 1))) & 0x0001; /* eg: right shift selected byte 5 times to get 3rd bit * (bitPos = 2) at rightmost position and * then AND with 0x0001*/ return value; } private void setBitInArray(byte[] input, int pos, int value) { int bytePos = pos / 8; int bitPos = pos % 8; byte old = input[bytePos]; old = (byte) (((0xFF7F >> bitPos) & old) & 0x00FF); byte newByte = (byte) ((value << (8 - (bitPos + 1))) | old); input[bytePos] = newByte; } private byte[] hexStringToByteArray(String string) { int length = string.length(); int n = (int)Math.ceil((length + 1) / 2); byte[] result = new byte[n]; for (int i = length - 1; i >= 0 ; i -= 2) { if (i == 0) { result[i / 2] = (byte) ((Character.digit('0', 16) << 4) + Character.digit(string.charAt(i), 16)); } else { result[i / 2] = (byte) ((Character.digit(string.charAt(i - 1), 16) << 4) + Character.digit(string.charAt(i), 16)); } } return result; } private void printBytes(byte[] input) { for (int i = 0 ; i < input.length; i++) { System.out.print(byteToBits(input[i]) + " "); } System.out.println(); } private String byteToBits(byte b) { StringBuffer buffer = new StringBuffer(); for (int i = 0 ; i < 8 ; i++) buffer.append((int)(b >> (8-(i+1)) & 0x0001)); return buffer.toString(); } private byte[] getBits(byte[] input, int startPos, int length) { int noOfBytes = (length-1)/8 + 1; byte[] output = new byte[noOfBytes]; for (int i = 0 ; i < length ; i++) { int value = getBitFromArray(input, startPos + i); setBitInArray(output, i, value); } return output; } private byte[] rotateLeft(byte[] input, int step, int length) { int noOfBytes = (length - 1) / 8 + 1; byte[] output = new byte[noOfBytes]; for (int i = 0 ; i < length ; i++) { int value = getBitFromArray(input, (i + step) % length); setBitInArray(output, i, value); } return output; } private byte[] concatBits(byte[] one, int oneLength, byte[] two, int twoLength) { int noOfBytes = (oneLength + twoLength - 1) / 8 + 1; byte[] output = new byte[noOfBytes]; int i = 0, j = 0; for (; i < oneLength ; i++) { int value = getBitFromArray(one, i); setBitInArray(output, j, value); j++; } for (i = 0 ; i < twoLength ; i++) { int value = getBitFromArray(two, i); setBitInArray(output, j, value); j++; } return output; } private byte[][] getSubKeys(byte[] masterKey) { int noOfSubKeys = SHIFTS.length; int keySize = PC1.length; byte[] key = permute(masterKey, PC1); byte[][] subKeys = new byte[noOfSubKeys][keySize]; byte[] leftHalf = getBits(key, 0, keySize/2); byte[] rightHalf = getBits(key, keySize/2, keySize/2); for (int i = 0 ; i < noOfSubKeys ; i++) { leftHalf = rotateLeft(leftHalf, SHIFTS[i], keySize/2); rightHalf = rotateLeft(rightHalf, SHIFTS[i], keySize/2); byte[] subKey = concatBits(leftHalf, keySize/2, rightHalf, keySize/2); subKeys[i] = permute(subKey, PC2); } return subKeys; } public byte[] crypt(byte[] message, byte[] key, String operation) { if (message.length < 8) { System.out.println("Message should be atleast 64 bits"); System.exit(1); } if (key.length != 8) { System.out.println("Key should be 64 bits"); System.exit(1); } int length = message.length; int n = (length + 7)/8 * 8; byte[] cipher = new byte[n]; if (length == 8) { return cryptText(message, key, operation); } int i = 0; int k = 0; while (i < length) { byte[] block = new byte[8]; byte[] result = new byte[8]; int j = 0; for (; j < 8 && i < length; j++, i++) { block[j] = message[i]; } while (j < 8) { block[j++] = 0x00; } System.out.println("BLOCK: "); printBytes(block); result = cryptText(block, key, operation); System.out.println("RESULT: "); printBytes(result); for (j = 0 ; j < 8 && k < cipher.length; j++, k++) { cipher[k] = result[j]; } } return cipher; } public byte[] cryptText(byte[] message, byte[] key, String operation) { if (message.length != 8) { System.out.println("Message should be 64 bits"); System.exit(1); } if (key.length != 8) { System.out.println("Key should be 64 bits"); System.exit(1); } byte[] result = null; int blockSize = IP.length; byte[][] subKeys = getSubKeys(key); int noOfRounds = subKeys.length; /** * Initial Permutation */ message = permute(message, IP); /** * Split message into two halves */ byte[] leftHalf = getBits(message, 0, blockSize/2); byte[] rightHalf = getBits(message, blockSize/2, blockSize/2); for (int i = 0 ; i < noOfRounds ; i++) { byte[] temp = rightHalf; /** * Expansion */ rightHalf = permute(rightHalf, E); /** * XOR rightHalf with roundKey */ byte[] roundKey = null; if (operation.equalsIgnoreCase("encrypt")) { roundKey = subKeys[i]; } else if (operation.equalsIgnoreCase("decrypt")) { roundKey = subKeys[noOfRounds - i - 1]; } else { System.out.println("Unsupported operation"); System.exit(0); } rightHalf = performXOR(rightHalf, roundKey); /** * S-Box */ rightHalf = sBox(rightHalf); /** * Permutation */ rightHalf = permute(rightHalf, P); /** * XOR rightHalf with leftHalf */ rightHalf = performXOR(rightHalf, leftHalf); /** * L(i) = R(i-1) */ leftHalf = temp; } /** * 32 bit swap */ byte[] concatHalves = concatBits(rightHalf, blockSize/2, leftHalf, blockSize/2); /** * Inverse Initial Permutation */ result = permute(concatHalves, IIP); return result; } private byte[] sBox(byte[] input) { /** * Split input to 6-bit blocks */ input = split(input,6); byte[] output = new byte[input.length/2]; int leftHalf = 0; for (int i = 0; i < input.length ; i++) { byte block = input[i]; /** * row - first and last bits * column - 4 bits in the middle */ int row = 2 * (block >> 7 & 0x0001) + (block >> 2 & 0x0001); int col = block >> 3 & 0x000F; int[] selectedSBox = getSBox(i); int rightHalf = selectedSBox[16 * row + col]; if (i % 2 == 0) { leftHalf = rightHalf; } else { output[i/2] = (byte) (16 * leftHalf + rightHalf); leftHalf = 0; } } return output; } private int[] getSBox(int i) { switch (i) { case 0: return S1; case 1: return S2; case 2: return S3; case 3: return S4; case 4: return S5; case 5: return S6; case 6: return S7; case 7: return S8; default: return null; } } private byte[] split(byte[] input, int length) { int noOfBytes = (8 * input.length - 1) / length + 1; byte[] output = new byte[noOfBytes]; for (int i = 0 ; i < noOfBytes ; i++) { for (int j = 0; j < length ; j++) { int value = getBitFromArray(input, length * i + j); setBitInArray(output, 8 * i + j, value); } } return output; } public static void main(String[] args) { DES des = new DES(); byte[] message = des.hexStringToByteArray("123456789ABCDEF"); System.out.println("PLAIN TEXT:"); des.printBytes(message); byte[] key = des.hexStringToByteArray("133457799BBCDFF1"); System.out.println("KEY:"); des.printBytes(key); byte[] cipher = des.crypt(message, key, "encrypt"); System.out.println("CIPHER TEXT:"); des.printBytes(cipher); byte[] result = des.crypt(cipher, key, "decrypt"); System.out.println("DECRYPTED TEXT:"); des.printBytes(result); } }
Output
dhanoopbhaskar@dhanoop-laptop:~$ javac DES.java
dhanoopbhaskar@dhanoop-laptop:~$ java DES
PLAIN TEXT:
00000001 00100011 01000101 01100111 10001001 10101011 11001101 11101111
KEY:
00010011 00110100 01010111 01111001 10011011 10111100 11011111 11110001
CIPHER TEXT:
10000101 11101000 00010011 01010100 00001111 00001010 10110100 00000101
DECRYPTED TEXT:
00000001 00100011 01000101 01100111 10001001 10101011 11001101 11101111
dhanoopbhaskar@dhanoop-laptop:~$
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