Note that these are ONLY basic level programs for easy understanding of the Data Encryption Standard (DES) algorithm
Key Generation - DESkeygen.java
import java.io.File;
import java.io.FileWriter;
public class DESkeygen {
private final File file = new File("DESkey.txt");
private final int KEY_LENGTH = 16;
private final static char[] hexArray = "0123456789ABCDEF".toCharArray();
public DESkeygen() {
try {
FileWriter fileWriter = new FileWriter(file);
fileWriter.write("");
for (int i = 0; i < KEY_LENGTH; i++) {
double random = Math.random();
int index = (int) (random * 16);
fileWriter.append(hexArray[index]);
fileWriter.flush();
}
fileWriter.close();
System.out.println("Key generated and saved in " + file.getName());
} catch (Exception exp) {
exp.printStackTrace();
}
}
public static void main(String[] args) {
new DESkeygen();
}
}Encryption - DESencrypt.java
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.Arrays;
public class DESencrypt {
private String mode = null;
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
/* 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 DESencrypt() {
this.mode = "ECB";
}
public DESencrypt(String mode) {
this.mode = mode;
}
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;
}
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
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) {
if (mode.equals("ECB")) {
return cryptText(message, key, operation);
} else if (mode.equals("CBC")) {
byte[] iv = getInitializationVector();
message = XORBytes(message, iv);
return cryptText(message, key, operation);
} else if (mode.equals("OFB")) {
byte[] nounce = getNounce();
byte[] temp = cryptText(nounce, key, operation);
byte[] result = XORBytes(temp, message);
return result;
} else if (mode.equals("CFB")) {
} else {
System.out.println("Unsupported mode of operation!");
return null;
}
}
int i = 0;
int k = 0;
byte[] feedback = new byte[8];
if (mode.equals("CBC")) {
feedback = getInitializationVector();
} else if (mode.equals("OFB")) {
feedback = getNounce();
} else if (mode.equals("CFB")) {
feedback = getInitializationVectorCFB();
}
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) {
/* pad with white spaces */
block[j++] = 0x20;
}
// System.out.println("BLOCK: ");
// printBytes(block);
if (mode.equals("ECB")) {
result = cryptText(block, key, operation);
} else if (mode.equals("CBC")) {
if (operation.equals("encrypt")) {
block = XORBytes(block, feedback);
result = cryptText(block, key, operation);
feedback = Arrays.copyOfRange(result, 0, 8);
} else if (operation.equals("decrypt")) {
result = cryptText(block, key, operation);
result = XORBytes(result, feedback);
feedback = Arrays.copyOfRange(block, 0, 8);
}
} else if (mode.equals("OFB")) {
result = cryptText(feedback, key, operation);
feedback = Arrays.copyOfRange(result, 0, 8);
result = XORBytes(result, block);
} else if (mode.equals("CFB")) {
if (operation.equals("encrypt")) {
result = cryptText(feedback, key, operation);
byte[] resultPart = Arrays.copyOfRange(result, 0, 4);
byte[] blockPart = Arrays.copyOfRange(block, 0, 4);
byte[] temp1 = XORBytes(resultPart, blockPart);
feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), temp1);
resultPart = Arrays.copyOfRange(result, 4, 8);
blockPart = Arrays.copyOfRange(block, 4, 8);
result = cryptText(feedback, key, operation);
byte[] temp2 = XORBytes(resultPart, blockPart);
feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), temp2);
result = mergeBytes(temp1, temp2);
} else if (operation.equals("decrypt")) {
result = cryptText(feedback, key, "encrypt");
byte[] resultPart = Arrays.copyOfRange(result, 0, 4);
byte[] blockPart = Arrays.copyOfRange(block, 0, 4);
byte[] temp1 = XORBytes(resultPart, blockPart);
feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), blockPart);
resultPart = Arrays.copyOfRange(result, 4, 8);
blockPart = Arrays.copyOfRange(block, 4, 8);
result = cryptText(feedback, key, "encrypt");
byte[] temp2 = XORBytes(resultPart, blockPart);
feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), blockPart);
result = mergeBytes(temp1, temp2);
}
} else {
System.out.println("Unsupported mode of operation!");
return null;
}
// System.out.println("RESULT: ");
// printBytes(result);
for (j = 0; j < 8 && k < cipher.length; j++, k++) {
cipher[k] = result[j];
}
}
return cipher;
}
private byte[] getInitializationVector() {
return hexStringToByteArray("DCBE6AE7EA5D5C61");
}
private byte[] getInitializationVectorCFB() {
return hexStringToByteArray("A5D5C61EFADB4351");
}
private byte[] getNounce() {
// char[] hexArray = "0123456789ABCDEF".toCharArray();
// String nounceStr = "";
// for (int i = 0 ; i < 16 ; i++) {
// double random = Math.random();
// int index = (int) (random * 16);
// nounceStr += hexArray[index];
// }
// return hexStringToByteArray(nounceStr);
return hexStringToByteArray("DCBE6AE7EA5D5C61");
}
private byte[] mergeBytes(byte[] in1, byte[] in2) {
byte[] out = new byte[in1.length + in2.length];
int i = 0;
for (int j = 0; j < in1.length; j++) {
out[i++] = in1[j];
}
for (int j = 0; j < in2.length; j++) {
out[i++] = in2[j];
}
return out;
}
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;
}
public static byte[] XORBytes(byte[] in1, byte[] in2) {
byte[] out = new byte[in1.length];
for (int i = 0; i < in1.length; i++) {
out[i] = (byte) ((in1[i] ^ in2[i]) & 0xff);
}
return out;
}
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) {
try {
if (args.length != 1) {
System.out.println("Usage: java < classname > < mode >" + "\n\t< mode > := (ECB|CBC|OFB|CFB)");
return;
}
/* ECB, CBC, OFB, or CFB */
String mode = args[0];
mode = mode.toUpperCase();
DESencrypt des = new DESencrypt(mode);
File keyFile = new File("DESkey.txt");
File textFile = new File("DESplaintext.txt");
File cipherFile = new File("DESciphertext.txt");
FileReader keyFileReader = new FileReader(keyFile);
BufferedReader bufferedReader = new BufferedReader(keyFileReader);
FileInputStream textFileInputStream = new FileInputStream(textFile);
FileOutputStream cipherFileOutputStream = new FileOutputStream(cipherFile);
byte[] key = new byte[(int) keyFile.length()];
String keyString = bufferedReader.readLine();
key = des.hexStringToByteArray(keyString);
byte[] message = new byte[(int) textFile.length()];
textFileInputStream.read(message);
byte[] cipher = des.crypt(message, key, "encrypt");
cipherFileOutputStream.write(cipher);
cipherFileOutputStream.flush();
cipherFileOutputStream.close();
bufferedReader.close();
textFileInputStream.close();
System.out.println("Encryption done! Please check DESciphertext.txt for output!");
} catch (Exception exp) {
exp.printStackTrace();
}
}
}Decryption - DESdecrypt.java
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.Arrays;
public class DESdecrypt {
private String mode = null;
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
/* 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 DESdecrypt() {
this.mode = "ECB";
}
public DESdecrypt(String mode) {
this.mode = mode;
}
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;
}
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
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) {
if (mode.equals("ECB")) {
return cryptText(message, key, operation);
} else if (mode.equals("CBC")) {
byte[] iv = getInitializationVector();
message = XORBytes(message, iv);
return cryptText(message, key, operation);
} else if (mode.equals("OFB")) {
byte[] nounce = getNounce();
byte[] temp = cryptText(nounce, key, "encrypt");
byte[] result = XORBytes(temp, message);
return result;
} else if (mode.equals("CFB")) {
} else {
System.out.println("Unsupported mode of operation!");
return null;
}
}
int i = 0;
int k = 0;
byte[] feedback = new byte[8];
if (mode.equals("CBC")) {
feedback = getInitializationVector();
} else if (mode.equals("OFB")) {
feedback = getNounce();
} else if (mode.equals("CFB")) {
feedback = getInitializationVectorCFB();
}
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) {
/* pad with white spaces */
block[j++] = 0x20;
}
// System.out.println("BLOCK: ");
// printBytes(block);
if (mode.equals("ECB")) {
result = cryptText(block, key, operation);
} else if (mode.equals("CBC")) {
if (operation.equals("encrypt")) {
block = XORBytes(block, feedback);
result = cryptText(block, key, operation);
feedback = Arrays.copyOfRange(result, 0, 8);
} else if (operation.equals("decrypt")) {
result = cryptText(block, key, operation);
result = XORBytes(result, feedback);
feedback = Arrays.copyOfRange(block, 0, 8);
}
} else if (mode.equals("OFB")) {
result = cryptText(feedback, key, "encrypt");
feedback = Arrays.copyOfRange(result, 0, 8);
result = XORBytes(result, block);
} else if (mode.equals("CFB")) {
if (operation.equals("encrypt")) {
result = cryptText(feedback, key, operation);
byte[] resultPart = Arrays.copyOfRange(result, 0, 4);
byte[] blockPart = Arrays.copyOfRange(block, 0, 4);
byte[] temp1 = XORBytes(resultPart, blockPart);
feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), temp1);
resultPart = Arrays.copyOfRange(result, 4, 8);
blockPart = Arrays.copyOfRange(block, 4, 8);
result = cryptText(feedback, key, operation);
byte[] temp2 = XORBytes(resultPart, blockPart);
feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), temp2);
result = mergeBytes(temp1, temp2);
} else if (operation.equals("decrypt")) {
result = cryptText(feedback, key, "encrypt");
byte[] resultPart = Arrays.copyOfRange(result, 0, 4);
byte[] blockPart = Arrays.copyOfRange(block, 0, 4);
byte[] temp1 = XORBytes(resultPart, blockPart);
feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), blockPart);
resultPart = Arrays.copyOfRange(result, 4, 8);
blockPart = Arrays.copyOfRange(block, 4, 8);
result = cryptText(feedback, key, "encrypt");
byte[] temp2 = XORBytes(resultPart, blockPart);
feedback = mergeBytes(Arrays.copyOfRange(result, 4, 8), blockPart);
result = mergeBytes(temp1, temp2);
}
} else {
System.out.println("Unsupported mode of operation!");
return null;
}
// System.out.println("RESULT: ");
// printBytes(result);
for (j = 0; j < 8 && k < cipher.length; j++, k++) {
cipher[k] = result[j];
}
}
return cipher;
}
private byte[] getInitializationVector() {
return hexStringToByteArray("DCBE6AE7EA5D5C61");
}
private byte[] getInitializationVectorCFB() {
return hexStringToByteArray("A5D5C61EFADB4351");
}
private byte[] getNounce() {
// char[] hexArray = "0123456789ABCDEF".toCharArray();
// String nounceStr = "";
// for (int i = 0 ; i < 16 ; i++) {
// double random = Math.random();
// int index = (int) (random * 16);
// nounceStr += hexArray[index];
// }
// return hexStringToByteArray(nounceStr);
return hexStringToByteArray("DCBE6AE7EA5D5C61");
}
private byte[] mergeBytes(byte[] in1, byte[] in2) {
byte[] out = new byte[in1.length + in2.length];
int i = 0;
for (int j = 0; j < in1.length; j++) {
out[i++] = in1[j];
}
for (int j = 0; j < in2.length; j++) {
out[i++] = in2[j];
}
return out;
}
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;
}
public static byte[] XORBytes(byte[] in1, byte[] in2) {
byte[] out = new byte[in1.length];
for (int i = 0; i < in1.length; i++) {
out[i] = (byte) ((in1[i] ^ in2[i]) & 0xff);
}
return out;
}
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) {
try {
if (args.length != 1) {
System.out.println("Usage: java < classname > < mode >" + "\n\t< mode > := (ECB|CBC|OFB|CFB)");
return;
}
/* ECB, CBC, OFB, or CFB */
String mode = args[0];
mode = mode.toUpperCase();
DESdecrypt des = new DESdecrypt(mode);
File keyFile = new File("DESkey.txt");
File textFile = new File("DESplaintext.txt");
File cipherFile = new File("DESciphertext.txt");
FileReader keyFileReader = new FileReader(keyFile);
BufferedReader bufferedReader = new BufferedReader(keyFileReader);
FileInputStream cipherFileInputStream = new FileInputStream(cipherFile);
FileOutputStream textFileOutputStream = new FileOutputStream(textFile);
byte[] key = new byte[(int) keyFile.length()];
String keyString = bufferedReader.readLine();
key = des.hexStringToByteArray(keyString);
byte[] cipher = new byte[(int) cipherFile.length()];
cipherFileInputStream.read(cipher);
byte[] message = des.crypt(cipher, key, "decrypt");
textFileOutputStream.write(message);
textFileOutputStream.flush();
textFileOutputStream.close();
bufferedReader.close();
cipherFileInputStream.close();
System.out.println("Decryption done! Please check DESplaintext.txt for output!");
} catch (Exception exp) {
exp.printStackTrace();
}
}
}
Output
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESkeygen
Key generated and saved in DESkey.txt
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt
Usage: java <classname> <mode>
<mode> := (ECB|CBC|OFB|CFB)
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt ecb
Encryption done! Please check DESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt ecb
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt cbc
Encryption done! Please check DESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt cbc
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt ofb
Encryption done! Please check DESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt ofb
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESencrypt cfb
Encryption done! Please check DESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt cfb
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$ java DESdecrypt cfb
Decryption done! Please check DESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace$
About Input/Output Files
DESkeygen.java - (output) DESkey.txt
DESencrypt.java - (input) DESkey.txt & DESplaintext.txt (output) DESciphertext.txt
DESdecrypt.java - (input) DESkey.txt & DESciphertext.txt (output) DESplaintext.txt