DES Algorithm Implementation program

 

DES Algorithm Implementation

#include <stdio.h>
 
int Original_key [64] = {
0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0,
0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1,
1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0,
1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1
};
 
int Permutated_Choice1[56] = {
  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
};
 
int Permutated_Choice2[48] = {
  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
};
 
int Iintial_Permutation [64] = {
  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
};
 
int Final_Permutation[] =
{
  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
};
 
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
};
 
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
};
 
int S1[4][16] =
{
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
};
 
int S2[4][16] =
{
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
};
 
int S3[4][16] =
{
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
};
 
int S4[4][16] =
{
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
};
 
int S5[4][16] =
{
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
};
 
int S6[4][16] =
{
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
};
 
int S7[4][16]=
{
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
};
 
int S8[4][16]=
{
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 shifts_for_each_round[16] = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };
int _56bit_key[56];
int _48bit_key[17][48];
int text_to_bits[99999], bits_size=0;
int Left32[17][32], Right32[17][32];
int EXPtext[48];
int XORtext[48];
int X[8][6];
int X2[32];
int R[32];
int chiper_text[64];
int encrypted_text[64];
 
int XOR(int a, int b) {
return (a ^ b);
}
 
void Dec_to_Binary(int n)
{
    int binaryNum[1000];
    int i = 0;
    while (n > 0) {
        binaryNum[i] = n % 2;
        n = n / 2;
        i++;
    }
    for (int j = i - 1; j >= 0; j--) {
text_to_bits[bits_size++] = binaryNum[j];
}
}
 
int F1(int i)
{
int r, c, b[6];
for (int j = 0; j < 6; j++)
b[j] = X[i][j];
 
r = b[0] * 2 + b[5];
c = 8 * b[1] + 4 * b[2] + 2 * b[3] + b[4];
if (i == 0)
return S1[r][c];
else if (i == 1)
return S2[r][c];
else if (i == 2)
return S3[r][c];
else if (i == 3)
return S4[r][c];
else if (i == 4)
return S5[r][c];
else if (i == 5)
return S6[r][c];
else if (i == 6)
return S7[r][c];
else if (i == 7)
return S8[r][c];
}
 
 
int PBox(int pos, int bit)
{
int i;
for (i = 0; i < 32; i++)
if (P[i] == pos + 1)
break;
R[i] = bit;
}
 
int ToBits(int value)
{
int k, j, m;
static int i;
if (i % 32 == 0)
i = 0;
for (j = 3; j >= 0; j--)
{
m = 1 << j;
k = value & m;
if (k == 0)
X2[3 - j + i] = '0' - 48;
else
X2[3 - j + i] = '1' - 48;
}
i = i + 4;
}
 
int SBox(int XORtext[])
{
int k = 0;
for (int i = 0; i < 8; i++)
for (int j = 0; j < 6; j++)
X[i][j] = XORtext[k++];
 
int value;
for (int i = 0; i < 8; i++)
{
value = F1(i);
ToBits(value);
}
}
 
void expansion_function(int pos, int bit)
{
for (int i = 0; i < 48; i++)
if (E[i] == pos + 1)
EXPtext[i] = bit;
}
 
void cipher(int Round, int mode)
{
for (int i = 0; i < 32; i++)
expansion_function(i, Right32[Round - 1][i]);
 
for (int i = 0; i < 48; i++)
{
if (mode == 0)
XORtext[i] = XOR(EXPtext[i], _48bit_key[Round][i]);
else
XORtext[i] = XOR(EXPtext[i], _48bit_key[17 - Round][i]);
}
 
SBox(XORtext);
 
for (int i = 0; i < 32; i++)
PBox(i, X2[i]);
for (int i = 0; i < 32; i++)
Right32[Round][i] = XOR(Left32[Round - 1][i], R[i]);
}
 
void finalPermutation(int pos, int bit)
{
int i;
for (i = 0; i < 64; i++)
if (Final_Permutation[i] == pos + 1)
break;
encrypted_text[i] = bit;
}
 
void Encrypt_each_64_bit (int plain_bits [])
{
int IP_result [64] , index=0;
for (int i = 0; i < 64; i++) {
IP_result [i] = plain_bits[ Iintial_Permutation[i] ];
}
for (int i = 0; i < 32; i++)
Left32[0][i] = IP_result[i];
for (int i = 32; i < 64; i++)
Right32[0][i - 32] = IP_result[i];
 
for (int k = 1; k < 17; k++)
{ // processing through all 16 rounds
cipher(k, 0);
 
for (int i = 0; i < 32; i++)
Left32[k][i] = Right32[k - 1][i]; // right part comes as it is to next round left part
}
 
for (int i = 0; i < 64; i++)
{ // 32bit swap as well as Final Inverse Permutation
if (i < 32)
chiper_text[i] = Right32[16][i];
else
chiper_text[i] = Left32[16][i - 32];
finalPermutation(i, chiper_text[i]);
}
 
for (int i = 0; i < 64; i++)
printf("%d", encrypted_text[i]);
}
 
 
void convert_Text_to_bits(char *plain_text){
for(int i=0;plain_text[i];i++){
int asci = plain_text[i];
Dec_to_Binary(asci);
}
}
 
void key56to48(int round, int pos, int bit)
{
int i;
for (i = 0; i < 56; i++)
if (Permutated_Choice2[i] == pos + 1)
break;
_48bit_key[round][i] = bit;
}
 
int key64to56(int pos, int bit)
{
int i;
for (i = 0; i < 56; i++)
if (Permutated_Choice1[i] == pos + 1)
break;
_56bit_key[i] = bit;
}
 
void key64to48(int key[])
{
int k, backup[17][2];
int CD[17][56];
int C[17][28], D[17][28];
 
for (int i = 0; i < 64; i++)
key64to56(i, key[i]);
 
for (int i = 0; i < 56; i++)
if (i < 28)
C[0][i] = _56bit_key[i];
else
D[0][i - 28] = _56bit_key[i];
 
for (int x = 1; x < 17; x++)
{
int shift = shifts_for_each_round[x - 1];
 
for (int i = 0; i < shift; i++)
backup[x - 1][i] = C[x - 1][i];
for (int i = 0; i < (28 - shift); i++)
C[x][i] = C[x - 1][i + shift];
k = 0;
for (int i = 28 - shift; i < 28; i++)
C[x][i] = backup[x - 1][k++];
 
for (int i = 0; i < shift; i++)
backup[x - 1][i] = D[x - 1][i];
for (int i = 0; i < (28 - shift); i++)
D[x][i] = D[x - 1][i + shift];
k = 0;
for (int i = 28 - shift; i < 28; i++)
D[x][i] = backup[x - 1][k++];
}
 
for (int j = 0; j < 17; j++)
{
for (int i = 0; i < 28; i++)
CD[j][i] = C[j][i];
for (int i = 28; i < 56; i++)
CD[j][i] = D[j][i - 28];
}
 
for (int j = 1; j < 17; j++)
for (int i = 0; i < 56; i++)
key56to48(j, i, CD[j][i]);
}
 
int main(){
char plain_text[] = "tomarrow we wiil be declaring war";
convert_Text_to_bits(plain_text);
key64to48(Original_key); // it creates all keys for all rounds
int _64bit_sets = bits_size/64;
printf("Decrypted output is\n");
for(int i=0;i<= _64bit_sets ;i++) {
Encrypt_each_64_bit (text_to_bits + 64*i);
}
return 0;
}



output:

Decrypted output is

0000111001101001001100011010111010010110111010111111111000010111001011111011111101010011011101011011000000111011100100000010110101000101011000011001000000101000001010011110101001011000111010011001110010110011011110110001101110000000001000001001000110111010

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