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des.java
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des.java
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import java.util.*;
class Main {
private static class DES {
// CONSTANTS
// Initial Permutation Table
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 Table
int[] IP1 = { 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 };
// first key-hePermutation Table
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 };
// second key-Permutation Table
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 };
// Expansion D-box Table
int[] EP = { 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 };
// Straight Permutation Table
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-box Table
int[][][] sbox = {
{ { 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 } },
{ { 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 } },
{ { 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 } },
{ { 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 } },
{ { 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 } },
{ { 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 } },
{ { 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 } },
{ { 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 } } };
int[] shiftBits = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };
// hexadecimal to binary conversion
String hextoBin(String input)
{
int n = input.length() * 4;
input = Long.toBinaryString(
Long.parseUnsignedLong(input, 16));
while (input.length() < n)
input = "0" + input;
return input;
}
// binary to hexadecimal conversion
String binToHex(String input)
{
int n = (int)input.length() / 4;
input = Long.toHexString(
Long.parseUnsignedLong(input, 2));
while (input.length() < n)
input = "0" + input;
return input;
}
// per-mutate input hexadecimal
// according to specified sequence
String permutation(int[] sequence, String input)
{
String output = "";
input = hextoBin(input);
for (int i = 0; i < sequence.length; i++)
output += input.charAt(sequence[i] - 1);
output = binToHex(output);
return output;
}
// xor 2 hexadecimal strings
String xor(String a, String b)
{
// hexadecimal to decimal(base 10)
long t_a = Long.parseUnsignedLong(a, 16);
// hexadecimal to decimal(base 10)
long t_b = Long.parseUnsignedLong(b, 16);
// xor
t_a = t_a ^ t_b;
// decimal to hexadecimal
a = Long.toHexString(t_a);
// prepend 0's to maintain length
while (a.length() < b.length())
a = "0" + a;
return a;
}
// left Circular Shifting bits
String leftCircularShift(String input, int numBits)
{
int n = input.length() * 4;
int perm[] = new int[n];
for (int i = 0; i < n - 1; i++)
perm[i] = (i + 2);
perm[n - 1] = 1;
while (numBits-- > 0)
input = permutation(perm, input);
return input;
}
// preparing 16 keys for 16 rounds
String[] getKeys(String key)
{
String keys[] = new String[16];
// first key permutation
key = permutation(PC1, key);
for (int i = 0; i < 16; i++) {
key = leftCircularShift( key.substring(0, 7), shiftBits[i]) + leftCircularShift(key.substring(7, 14), shiftBits[i]);
// second key permutation
keys[i] = permutation(PC2, key);
}
return keys;
}
// s-box lookup
String sBox(String input)
{
String output = "";
input = hextoBin(input);
for (int i = 0; i < 48; i += 6) {
String temp = input.substring(i, i + 6);
int num = i / 6;
int row = Integer.parseInt(
temp.charAt(0) + "" + temp.charAt(5), 2);
int col = Integer.parseInt(
temp.substring(1, 5), 2);
output += Integer.toHexString(
sbox[num][row][col]);
}
return output;
}
String round(String input, String key, int num)
{
// fk
String left = input.substring(0, 8);
String temp = input.substring(8, 16);
String right = temp;
// Expansion permutation
temp = permutation(EP, temp);
// xor temp and round key
temp = xor(temp, key);
// lookup in s-box table
temp = sBox(temp);
// Straight D-box
temp = permutation(P, temp);
// xor
left = xor(left, temp);
System.out.println("Round " + (num + 1) + " " + right.toUpperCase() + " " + left.toUpperCase() + " " + key.toUpperCase());
// swapper
return right + left;
}
String encrypt(String plainText, String key)
{
int i;
// get round keys
String keys[] = getKeys(key);
// initial permutation
plainText = permutation(IP, plainText);
System.out.println( "After initial permutation: " + plainText.toUpperCase());
System.out.println( "After splitting: L0=" + plainText.substring(0, 8).toUpperCase() + " R0=" + plainText.substring(8, 16).toUpperCase() + "\n");
// 16 rounds
for (i = 0; i < 16; i++) {
plainText = round(plainText, keys[i], i);
}
// 32-bit swap
plainText = plainText.substring(8, 16) + plainText.substring(0, 8);
// final permutation
plainText = permutation(IP1, plainText);
return plainText;
}
String decrypt(String plainText, String key)
{
int i;
// get round keys
String keys[] = getKeys(key);
// initial permutation
plainText = permutation(IP, plainText);
System.out.println( "After initial permutation: " + plainText.toUpperCase());
System.out.println("After splitting: L0=" + plainText.substring(0, 8).toUpperCase() + " R0=" + plainText.substring(8, 16).toUpperCase() + "\n");
// 16-rounds
for (i = 15; i > -1; i--) {
plainText = round(plainText, keys[i], 15 - i);
}
// 32-bit swap
plainText = plainText.substring(8, 16) + plainText.substring(0, 8);
plainText = permutation(IP1, plainText);
return plainText;
}
}
public static void main(String args[])
{
String text = "123456ABCD132536";
String key = "AABB09182736CCDD";
DES cipher = new DES();
System.out.println("Encryption:\n");
text = cipher.encrypt(text, key);
System.out.println( "\nCipher Text: " + text.toUpperCase() + "\n");
System.out.println("Decryption\n");
text = cipher.decrypt(text, key);
System.out.println( "\nPlain Text: " + text.toUpperCase());
}
}