Question

SDES C++

The code is not working currently I know the functions are correct but the original plaintext should match the "ciphertext after" when inputting 4

#include <iostream>
#include <iomanip>
#include <string>
#include <stdlib.h>
#include <stdio.h>
#include <cstdlib>
#include <time.h>
#include <windows.h>

using namespace std;
//function prototypes
void splitString(string &x, string &y, string &original);
void expansionFunction(string &input);
string XORstring(string& str1, string& str2);
string getSBOXValue(string arr[][8], string val);
int binaryToDecimal(int n);
string generateKey();
string findKey(string Key, int round);
string Encryption(string &plaintext, string key);
string Decryption(string& cipher, string key);

int main()
{
   string plaintext = "011100100110", key = "010011001";
   cout << "SDES Encryption|\n---------------|\n";
   cout << "Original Plaintext = " << plaintext;
   cout << "\nOriginal Key" << setw(9) <<" = " << key << endl;

  
   //split string int left and right
   string left, right;
  
   splitString(left, right, plaintext);
  
   cout << endl << "L0 = " << left << endl << "R0 = " << right << endl;
   cout << "\nL1 = R0" << endl;
   string l1 = right; //assign l1 to be r0

   //find r1
   //first expand r0
   string eRight = right;
   expansionFunction(eRight);
   //reduce key value by 1
   key.resize(key.size() - 1);
  
   cout << "\nXOR\n";
   cout << "E(Right) = " << eRight << endl;
   cout << "K1"<< setw(9) <<" = " << key << endl;
   cout << "--------------------------" << endl;
  
   // E(R0) xor k1
   string XORresult = XORstring(eRight, key);
   cout << setw(19) << XORresult;

   //split string into s1 and s2
   string S1BOX[2][8] = {"101","010","001","110","011","100","111","000","001","100","110","010","000","111","101","011"};
   string S2BOX[2][8] = {"100","000","110","101","111","001","011","010","101","011","000","111","110","010","001","100"};
  

   string s1, s2;
   splitString(s1, s2, XORresult);
  
   string s1result = getSBOXValue(S1BOX, s1);
   string s2result = getSBOXValue(S2BOX, s2);
   cout << "\nS1 = " << s1 << " = " << s1result << endl << "S2 = " << s2 << " = " << s2result << endl;
   string functionResult = s1result + s2result;
   cout << endl << "Result from SBOX's is = " << functionResult << endl;
   cout << "L0 XOR f(R0,K1) = " << XORstring(left, functionResult) << "(R1)\n";

   string ciphertext = right + XORstring(left, functionResult);
   cout << "\nCiphertext(L1R1) = " << ciphertext << endl;

   cout << "----------------------------------------------------------------------------------------\n" << endl;
   int rounds;
   cout << "Round SDES\n";
   key = generateKey();
   cout << endl;
   string saveKey = key;
   plaintext = "011100100110";
   cout << "Random Key = " << key << endl;
   cout << "Plaintext = " << plaintext << endl;
  
   cout << "\nSelect number of SDES rounds\n-> ";
   cin >> rounds;
   cout << endl;
   cout << "Plaintext = " << plaintext << endl << endl;
  
   for (int i = 0; i < rounds;   i++)
   {
       key = findKey(key, i+1);
       plaintext = Encryption(plaintext, key);
       cout << "Round " << i+1 << " Ciphertext = " << plaintext << endl;
   }
   ciphertext = "";
   ciphertext.append(plaintext, 6, 6);
   ciphertext.append(plaintext, 0, 6);

   cout << endl << "Ciphertext after " << rounds << " rounds: " << ciphertext << endl << endl;
   cout << "Proof by decryption:\n\n" << "Ciphertext: " << ciphertext << endl << endl;

   string d;
   d.append(ciphertext, 6, 6);
   d.append(ciphertext, 0, 6);
   for (int j = rounds; j > 0; j--)
   {
       key = findKey(saveKey, j);
       d = Decryption(d, key);
       if (j != 1)
           cout << "Round " << j << " Ciphertext = " << d << endl;
       else if (j == 1)
           cout << "\nSucceeding Plaintext is: " << d << endl;
   }  

return 0;
}
//function definitions
void splitString(string &x, string &y, string &original)
{
       x = original.substr(0, original.length() / 2);
       y = original.substr(original.length() / 2);
}

void expansionFunction(string &input)
{
   char temp;
   //add two more letters to meet size requirement
   input.append(input, 4, 2);
   temp = input[3];
   input[5] = input[2];
   input[4] = temp;
   input[3] = input[2];
   input[2] = temp;
}

string XORstring(string& str1, string& str2)
{
   string temp = str2;
   for (int i = 0; i < str2.length(); i++)
   {
       temp[i] = (str1[i] ^ str2[i]) + '0';
   }
   return temp;
  
}

string getSBOXValue(string arr[][8], string val)
{
   int column;
   if (val[0] == '0')
   {
       column = stoi(val.substr(1, val.length()));
       column = binaryToDecimal(column);
       for (int i = 0; i < 8; i++)
           if (i == column)
               return arr[0][i];
   }
   else
   {
       column = stoi(val.substr(1, val.length()));
       column = binaryToDecimal(column);
       for (int i = 0; i < 8; i++)
           if (i == column)
               return arr[1][i];
   }
              
}
int binaryToDecimal(int n)
{
   int decimal = 0;

   // Initializing base value to 1, i.e 2^0
   int base = 1;

   int temp = n;
   while (temp) {
       int last = temp % 10;
       temp = temp / 10;
       decimal += last * base;
       base = base * 2;
   }

   return decimal;
}
string generateKey()
{
   string randomKey;
   string binary[2] = { "0","1" };
   randomKey.reserve(8);
   srand(time(0));
   cout << "Generating KEY...\n";
   for (int i = 0; i < 9; i++)
   {
       randomKey += binary[rand()%2];
   }
   return randomKey;

}
string findKey(string Key, int round)
{
   string temp;
   //Get the key for the round
   if (round == 1)
       temp.append(Key, 0, 8);
   else if (round == 2)
       temp.append(Key, 1, 8);
   else if (round == 3)
   {
       temp.append(Key, 2, 7);
       temp.append(Key, 0, 1);
   }
   else if (round == 4)
   {
       temp.append(Key, 3, 6);
       temp.append(Key, 0, 2);
   }
   return temp;
}

string Encryption(string &plaintext, string key)
   {
   string left, right, eRight, result, s1, s2, Ln, Rn;
   string S1BOX[2][8] = { "101","010","001","110","011","100","111","000","001","100","110","010","000","111","101","011" };
   string S2BOX[2][8] = { "100","000","110","101","111","001","011","010","101","011","000","111","110","010","001","100" };
  
   splitString(left, right, plaintext);

   Ln = right; // Ln = Rn - 1
   eRight = right;
   //use expansion on right side
   expansionFunction(eRight);
   result = XORstring(eRight, key);
   splitString(s1, s2, result);

   string s1result = getSBOXValue(S1BOX, s1);
   string s2result = getSBOXValue(S2BOX, s2);

   string functionResult = s1result + s2result;
   Rn = XORstring(left, functionResult);
   return Ln + Rn; //L1R2
}

string Decryption(string& cipher, string key)
{
   string Left, Right, eRight, Ln, Rn, result, s1, s2;
   string S1BOX[2][8] = { "101","010","001","110","011","100","111","000","001","100","110","010","000","111","101","011" };
   string S2BOX[2][8] = { "100","000","110","101","111","001","011","010","101","011","000","111","110","010","001","100" };
   //find key
   splitString(Left, Right, cipher);
   Rn = Left;
   eRight = Rn;
   expansionFunction(eRight);
   result = XORstring(eRight, key);
   splitString(s1, s2, result);
   string s1result = getSBOXValue(S1BOX, s1);
   string s2result = getSBOXValue(S2BOX, s2);

   string functionResult = s1result + s2result;
   Ln = XORstring(Right, functionResult);
   return Ln + Rn;
}

Answer 1

#include <iostream>
#include <iomanip>
#include <string>
#include <stdlib.h>
#include <stdio.h>
#include <cstdlib>
#include <time.h>
#include <windows.h>

using namespace std;
//function prototypes
void splitString(string &x, string &y, string &original);
void expansionFunction(string &input);
string XORstring(string& str1, string& str2);
string getSBOXValue(string arr[][8], string val);
int binaryToDecimal(int n);
string generateKey();
string findKey(string Key, int round);
string Encryption(string &plaintext, string key);
string Decryption(string& cipher, string key);

int main()
{
   string plaintext = "011100100110", key = "010011001";
  
   cout << "SDES Encryption|\n---------------|\n";
   cout << "Original Plaintext = " << plaintext;
   cout << "\nOriginal Key" << setw(9) << " = " << key << endl;

   //split string int left and right
   string left, right;

   splitString(left, right, plaintext);

   cout << endl << "L0 = " << left << endl << "R0 = " << right << endl;
   cout << "\nL1 = R0" << endl;
   string l1 = right; //assign l1 to be r0

   //find r1
   //first expand r0
   string eRight = right;
   expansionFunction(eRight);
   //reduce key value by 1
   key.resize(key.size() - 1);

   cout << "\nXOR\n";
   cout << "E(Right) = " << eRight << endl;
   cout << "K1" << setw(9) << " = " << key << endl;
   cout << "--------------------------" << endl;

   // E(R0) xor k1
   string XORresult = XORstring(eRight, key);
   cout << setw(19) << XORresult;

   //split string into s1 and s2
   string S1BOX[2][8] = { "101","010","001","110","011","100","111","000","001","100","110","010","000","111","101","011" };
   string S2BOX[2][8] = { "100","000","110","101","111","001","011","010","101","011","000","111","110","010","001","100" };

   string s1, s2;
   splitString(s1, s2, XORresult);

   string s1result = getSBOXValue(S1BOX, s1);
   string s2result = getSBOXValue(S2BOX, s2);
   cout << "\nS1 = " << s1 << " = " << s1result << endl << "S2 = " << s2 << " = " << s2result << endl;
   string functionResult = s1result + s2result;
   cout << endl << "Result from SBOX's is = " << functionResult << endl;
   cout << "L0 XOR f(R0,K1) = " << XORstring(left, functionResult) << "(R1)\n";

   string ciphertext = right + XORstring(left, functionResult);
   cout << "\nCiphertext(L1R1) = " << ciphertext << endl;

   cout << "----------------------------------------------------------------------------------------\n" << endl;
   int rounds;
   cout << "Round SDES\n";
   key = generateKey();
   cout << endl;
   string saveKey = key;
   plaintext = "011100100110";
   cout << "Random Key = " << key << endl;
   cout << "Plaintext = " << plaintext << endl;

   cout << "\nSelect number of SDES rounds\n-> ";
   cin >> rounds;
   string *keyarray = new string[rounds];
   for (int i = 0; i < rounds; i++)
   {
       keyarray[i] = generateKey();
   }
   cout << "Plaintext = " << plaintext << endl << endl;

   for (int i = 0; i < rounds; i++)
   {
       key = keyarray[i];
       plaintext = Encryption(plaintext, key);
       cout << "Round " << i + 1 << " Ciphertext = " << plaintext << endl;
   }
   ciphertext = "";
   ciphertext.append(plaintext, 6, 6);
   ciphertext.append(plaintext, 0, 6);

   cout << endl << "Ciphertext after " << rounds << " rounds: " << ciphertext << endl << endl;
   cout << "Proof by decryption:\n\n" << "Ciphertext: " << ciphertext << endl << endl;

   string d;
   d.append(ciphertext, 6, 6);
   d.append(ciphertext, 0, 6);
   for (int j = rounds; j > 0; j--)
   {
       key = keyarray[rounds - j];
       d = Decryption(d, key);
       if (j != 1)
           cout << "Round " << j << " Ciphertext = " << d << endl;
       else if (j == 1)
           cout << "\nSucceeding Plaintext is: " << d << endl;
   }

   return 0;
}
//function definitions
void splitString(string &x, string &y, string &original)
{
   x = original.substr(0, original.length() / 2);
   y = original.substr(original.length() / 2);
}

void expansionFunction(string &input)
{
   char temp;
   //add two more letters to meet size requirement
   input.append(input, 4, 2);
   temp = input[3];
   input[5] = input[2];
   input[4] = temp;
   input[3] = input[2];
   input[2] = temp;
}

string XORstring(string& str1, string& str2)
{
   string temp = str2;
   for (int i = 0; i < str2.length(); i++)
   {
       temp[i] = (str1[i] ^ str2[i]) + '0';
   }
   return temp;

}

string getSBOXValue(string arr[][8], string val)
{
   int column;
   if (val[0] == '0')
   {
       column = stoi(val.substr(1, val.length()));
       column = binaryToDecimal(column);
       for (int i = 0; i < 8; i++)
           if (i == column)
               return arr[0][i];
   }
   else
   {
       column = stoi(val.substr(1, val.length()));
       column = binaryToDecimal(column);
       for (int i = 0; i < 8; i++)
           if (i == column)
               return arr[1][i];
   }

}
int binaryToDecimal(int n)
{
   int decimal = 0;

   // Initializing base value to 1, i.e 2^0
   int base = 1;

   int temp = n;
   while (temp) {
       int last = temp % 10;
       temp = temp / 10;
       decimal += last * base;
       base = base * 2;
   }

   return decimal;
}
string generateKey()
{
   string randomKey;
   string binary[2] = { "0","1" };
   randomKey.reserve(8);
   srand(time(0));
   cout << "Generating KEY...\n";
   for (int i = 0; i < 9; i++)
   {
       randomKey += binary[rand() % 2];
   }
   return randomKey;

}

string Encryption(string &plaintext, string key)
{
   string left, right, eRight, result, s1, s2, Ln, Rn;
   string S1BOX[2][8] = { "101","010","001","110","011","100","111","000","001","100","110","010","000","111","101","011" };
   string S2BOX[2][8] = { "100","000","110","101","111","001","011","010","101","011","000","111","110","010","001","100" };

   splitString(left, right, plaintext);

   Ln = right; // Ln = Rn - 1
   eRight = right;
   //use expansion on right side
   expansionFunction(eRight);
   result = XORstring(eRight, key);
   splitString(s1, s2, result);

   string s1result = getSBOXValue(S1BOX, s1);
   string s2result = getSBOXValue(S2BOX, s2);

   string functionResult = s1result + s2result;
   Rn = XORstring(left, functionResult);
   return Ln + Rn; //L1R2
}

string Decryption(string& cipher, string key)
{
   string Left, Right, eRight, Ln, Rn, result, s1, s2;
   string S1BOX[2][8] = { "101","010","001","110","011","100","111","000","001","100","110","010","000","111","101","011" };
   string S2BOX[2][8] = { "100","000","110","101","111","001","011","010","101","011","000","111","110","010","001","100" };
   //find key
   splitString(Left, Right, cipher);
   Rn = Left;
   eRight = Rn;
   expansionFunction(eRight);
   result = XORstring(eRight, key);
   splitString(s1, s2, result);
   string s1result = getSBOXValue(S1BOX, s1);
   string s2result = getSBOXValue(S2BOX, s2);

   string functionResult = s1result + s2result;
   Ln = XORstring(Right, functionResult);
   return Ln + Rn;
}

OUTPUT:

SDES Encryption|
---------------|
Original Plaintext = 011100100110
Original Key = 010011001

L0 = 011100
R0 = 100110

L1 = R0

XOR
E(Right) = 10101010
K1 = 01001100
--------------------------
11100110
S1 = 1110 = 101
S2 = 0110 = 011

Result from SBOX's is = 101011
L0 XOR f(R0,K1) = 110111(R1)

Ciphertext(L1R1) = 100110110111
----------------------------------------------------------------------------------------

Round SDES
Generating KEY...

Random Key = 110000011
Plaintext = 011100100110

Select number of SDES rounds
-> 4
Generating KEY...
Generating KEY...
Generating KEY...
Generating KEY...
Plaintext = 011100100110

Round 1 Ciphertext = 100110001011
Round 2 Ciphertext = 001011001101
Round 3 Ciphertext = 001101000110
Round 4 Ciphertext = 000110111010

Ciphertext after 4 rounds: 111010000110

Proof by decryption:

Ciphertext: 111010000110

Round 4 Ciphertext = 001101000110
Round 3 Ciphertext = 001011001101
Round 2 Ciphertext = 100110001011

Succeeding Plaintext is: 011100100110

NOTE: findKey() gave away wrong key for decryption hence wrong value was generated.