#include <iostream>
#include <cctype>
using namespace std;
char encryptChar(char ch, int shift) {
 if (!isalpha(ch)) {
 return ch;
 }
 char base = isupper(ch) ? 'A' : 'a';
 ch = (ch - base + shift) % 26 + base;
 return ch;
}
string encryptString(const string& str, int shift) {
 string result;
 for (char ch : str) {
 result += encryptChar(ch, shift);
 }
 return result;
}
int main() {
 string str;
 int shift;
 cout << "Enter string to encrypt: ";
 getline(cin, str);
 cout << "Enter shift value: ";
 cin >> shift;
 string encrypted = encryptString(str, shift);
 cout << "Encrypted string: " << encrypted << endl;
 return 0;
}

#include <iostream>
#include <string>
using namespace std;
string decryptCaesarCipher(string ciphertext, int key) {
  string plaintext = "";
  for (char &c : ciphertext) {
    if (isalpha(c)) {
      char shifted = c - key;
      if (islower(c)) 
      {
        if (shifted < 'a') {
          shifted += 26;
        }
      } else 
      {
        if (shifted < 'A') {
          shifted += 26;
        }
      }
      plaintext += shifted;
    } else {
      plaintext += c;
    }
  }
  return plaintext;
}
int main() {
  string ciphertext = "vnnc vn jocna cqn cxpj yjach";

  for (int key = 0; key < 26; ++key) {
    string plaintext = decryptCaesarCipher(ciphertext, key);
    cout << "Key: " << key << ", Plain Text: " << plaintext << endl;
  }
  return 0;
}

//playfair
#include <cctype>
#include <iostream>
#include <string>
using namespace std;
void createKeySquare(const string &key, char square[5][5]) {
  int keyIndex = 0;
  for (int i = 0; i < 5; i++) {
    for (int j = 0; j < 5; j++) {
      if (keyIndex < key.length()) {
        char ch = toupper(key[keyIndex]);
        if (ch == 'J') {
          ch = 'I';
        }
        square[i][j] = ch;
        keyIndex++;
      } else {
        square[i][j] = 'X' + (i * 5 + j + 1) % 26;
      }
    }
  }
}
void findPosition(char ch, int &row, int &col, const char square[5][5]) {
  for (int i = 0; i < 5; i++) {
    for (int j = 0; j < 5; j++) {
      if (toupper(square[i][j]) == toupper(ch)) {
        row = i;
        col = j;
        return;
      }
    }
  }
}
string encryptPair(char ch1, char ch2, const char square[5][5]) {
  int row1, row2, col1, col2;
  findPosition(ch1, row1, col1, square);
  findPosition(ch2, row2, col2, square);
  if (row1 == row2) {
    ch1 = square[row1][(col1 + 1) % 5];
    ch2 = square[row2][(col2 + 1) % 5];
  } else if (col1 == col2) {
    ch1 = square[(row1 + 1) % 5][col1];
    ch2 = square[(row2 + 1) % 5][col2];
  } else {
    ch1 = square[row1][col2];
    ch2 = square[row2][col1];
  }
  return string(1, ch1) + string(1, ch2);
}
string encrypt(const string &plaintext, const string &key) {
  char square[5][5];
  createKeySquare(key, square);
  string ciphertext;
  for (int i = 0; i < plaintext.length(); i += 2) {
    char ch1 = toupper(plaintext[i]);
    char ch2 = (i + 1 < plaintext.length()) ? toupper(plaintext[i + 1]) : 'X';
    if (ch1 == ch2) {
      ch2 = 'X';
    }
    ciphertext += encryptPair(ch1, ch2, square);
  }
  return ciphertext;
}
int main() {
  string plaintext = "hi there";
  string key = "playfair";
  string ciphertext = encrypt(plaintext, key);
  cout << "Plaintext: " << plaintext << endl;
  cout << "Ciphertext: " << ciphertext << endl;
  return 0;
}


//vignere
#include <cctype>
#include <iostream>
#include <string>
using namespace std;
string encrypt(const string &plaintext, const string &key) {
  string ciphertext;
  int key_index = 0;
  for (char ch : plaintext) {
    if (isalpha(ch)) {
      char shift = toupper(key[key_index % key.length()]) - 'A';
      ch = toupper(ch) + shift;
      if (ch > 'Z') {
        ch -= 26;
      }
      ch = tolower(ch); 
    }
    ciphertext += ch;
    key_index++;
  }
  return ciphertext;
}
std::string decrypt(const string &ciphertext, const string &key) {
  std::string plaintext;
  int key_index = 0;
  for (char ch : ciphertext) {
    if (isalpha(ch)) {
      char shift = toupper(key[key_index % key.length()]) - 'A';
      ch = toupper(ch) - shift;
      if (ch < 'A') {
        ch += 26;
      }
      ch = tolower(ch);
    }
    plaintext += ch;
    key_index++;
  }
  return plaintext;
}
int main() {
  string plaintext = "hello world!";
  string key = "secret";
  string ciphertext = encrypt(plaintext, key);
  cout << "Ciphertext: " << ciphertext << endl;
  string decrypted = decrypt(ciphertext, key);
  cout << "Plaintext: " << decrypted << endl;
  return 0;
}

//hillcipher
#include <iostream>
using namespace std;
void getKeyMatrix(string key, int keyMatrix[][3]) {
  int k = 0;
  for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
      keyMatrix[i][j] = (key[k]) % 65;
      k++;
    }
  }
}
void encrypt(int cipherMatrix[][1], int keyMatrix[][3],
             int messageVector[][1]) {
  int x, i, j;
  for (i = 0; i < 3; i++) {
    for (j = 0; j < 1; j++) {
      cipherMatrix[i][j] = 0;

      for (x = 0; x < 3; x++) {
        cipherMatrix[i][j] += keyMatrix[i][x] * messageVector[x][j];
      }

      cipherMatrix[i][j] = cipherMatrix[i][j] % 26;
    }
  }
}
void HillCipher(string message, string key) {
  int keyMatrix[3][3];
  getKeyMatrix(key, keyMatrix);
  int messageVector[3][1];
  for (int i = 0; i < 3; i++)
    messageVector[i][0] = (message[i]) % 65;
  int cipherMatrix[3][1];
  encrypt(cipherMatrix, keyMatrix, messageVector);
  string CipherText;
  for (int i = 0; i < 3; i++)
    CipherText += cipherMatrix[i][0] + 65;
  cout << " Ciphertext:" << CipherText;
}
int main() {
  string message = "hello world";
  string key = "GYBNQKURP";
  HillCipher(message, key);
  return 0;
}


//des-encrypt
// Including dependencies
#include <iostream>
#include <string>
#include <cmath>

using namespace std;

// Array to hold 16 keys
string round_keys[16];

// String to hold the plain text
string pt;

// Function to convert a number in decimal to binary
string convertDecimalToBinary(int decimal)
{
    string binary;
    while(decimal != 0) {
        binary = (decimal%2 == 0 ? "0" : "1")+binary; 
        decimal = decimal/2;
    }
    while(binary.length() < 4){
        binary = "0"+binary;
    }
    return binary;
}

// Function to convert a number in binary to decimal
int convertBinaryToDecimal(string binary)
{
    int decimal = 0;
    int counter = 0;
    int size = binary.length();
    for (int i = size-1; i >= 0; i--)
    {
        if(binary[i] == '1'){
            decimal += pow(2, counter);
        }
    counter++;
    }
    return decimal;
}
// Function to do a circular left shift by 1
string shift_left_once(string key_chunk){ 
    string shifted="";  
        for(int i = 1; i < 28; i++){ 
            shifted += key_chunk[i]; 
        } 
        shifted += key_chunk[0];   
    return shifted; 
} 
// Function to do a circular left shift by 2
string shift_left_twice(string key_chunk){ 
    string shifted=""; 
    for(int i = 0; i < 2; i++){ 
        for(int j = 1; j < 28; j++){ 
            shifted += key_chunk[j]; 
        } 
        shifted += key_chunk[0]; 
        key_chunk= shifted; 
        shifted =""; 
    } 
    return key_chunk; 
}
// Function to compute xor between two strings
string Xor(string a, string b){ 
    string result = ""; 
    int size = b.size();
    for(int i = 0; i < size; i++){ 
        if(a[i] != b[i]){ 
            result += "1"; 
        }
        else{ 
            result += "0"; 
        } 
    } 
    return result; 
} 
// Function to generate the 16 keys.
void generate_keys(string key){
    // The PC1 table
    int pc1[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 
    };
    // The PC2 table
    int pc2[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 
    }; 
    // 1. Compressing the key using the PC1 table
    string perm_key =""; 
    for(int i = 0; i < 56; i++){ 
        perm_key+= key[pc1[i]-1]; 
    } 
    // 2. Dividing the key into two equal halves
    string left= perm_key.substr(0, 28); 
    string right= perm_key.substr(28, 28); 
    for(int i=0; i<16; i++){ 
        // 3.1. For rounds 1, 2, 9, 16 the key_chunks
        // are shifted by one.
        if(i == 0 || i == 1 || i==8 || i==15 ){
            left= shift_left_once(left); 
            right= shift_left_once(right);
        } 
        // 3.2. For other rounds, the key_chunks
        // are shifted by two
        else{
            left= shift_left_twice(left); 
            right= shift_left_twice(right);
        }
        // Combining the two chunks
        string combined_key = left + right;
        string round_key = ""; 
        // Finally, using the PC2 table to transpose the key bits
        for(int i = 0; i < 48; i++){ 
            round_key += combined_key[pc2[i]-1]; 
        }   
        round_keys[i] = round_key; 
    } 

}
// Implementing the algorithm
string DES(){ 
    // The initial permutation table 
    int initial_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 
    }; 
    // The expansion table
    int expansion_table[48] = { 
    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 
    }; 
    // The substitution boxes. The should contain values
    // from 0 to 15 in any order.
    int substition_boxes[8][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}
    }, 
    { 
    {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} 
    }};
    // The permutation table
    int permutation_tab[32] = { 
    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 
    }; 
    // The inverse permutation table
    int inverse_permutation[64]= { 
    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 
    };
    //1. Applying the initial permutation
    string perm = ""; 
    for(int i = 0; i < 64; i++){ 
        perm += pt[initial_permutation[i]-1]; 
    }  
    // 2. Dividing the result into two equal halves 
    string left = perm.substr(0, 32); 
    string right = perm.substr(32, 32);
    // The plain text is encrypted 16 times  
    for(int i=0; i<16; i++) { 
        string right_expanded = ""; 
        // 3.1. The right half of the plain text is expanded
        for(int i = 0; i < 48; i++) { 
            right_expanded += right[expansion_table[i]-1]; 
    };  // 3.3. The result is xored with a key
        string xored = Xor(round_keys[i], right_expanded);  
        string res = ""; 
        // 3.4. The result is divided into 8 equal parts and passed 
        // through 8 substitution boxes. After passing through a 
        // substitution box, each box is reduced from 6 to 4 bits.
        for(int i=0;i<8; i++){ 
            // Finding row and column indices to lookup the
            // substitution box
            string row1= xored.substr(i*6,1) + xored.substr(i*6 + 5,1);
            int row = convertBinaryToDecimal(row1);
            string col1 = xored.substr(i*6 + 1,1) + xored.substr(i*6 + 2,1) + xored.substr(i*6 + 3,1) + xored.substr(i*6 + 4,1);;
            int col = convertBinaryToDecimal(col1);
            int val = substition_boxes[i][row][col];
            res += convertDecimalToBinary(val);  
        } 
        // 3.5. Another permutation is applied
        string perm2 =""; 
        for(int i = 0; i < 32; i++){ 
            perm2 += res[permutation_tab[i]-1]; 
        }
        // 3.6. The result is xored with the left half
        xored = Xor(perm2, left);
        // 3.7. The left and the right parts of the plain text are swapped 
        left = xored; 
        if(i < 15){ 
            string temp = right;
            right = xored;
            left = temp;
        } 
    } 
    // 4. The halves of the plain text are applied
    string combined_text = left + right;   
    string ciphertext =""; 
    // The inverse of the initial permutation is applied
    for(int i = 0; i < 64; i++){ 
        ciphertext+= combined_text[inverse_permutation[i]-1]; 
    }
    //And we finally get the cipher text
    return ciphertext; 
}
int main(){ 
    // A 64 bit key
    // string key= "0001001100110100010101110111100110011011101111001101111111110001";

    string key;
    cout << "Enter the 64-bit key : ";
    getline(cin, key);

    // A block of plain text of 64 bits
    // pt= "0000000100100011010001010110011110001001101010111100110111101111";
    cout << "Enter the 64-bit plain text : ";
    getline(cin, pt);
    
    // Calling the function to generate 16 keys
    generate_keys(key); 
    cout<<"Plain text: "<<pt<<endl; 
    // Applying the algo
    string ct= DES(); 
    cout<<"Ciphertext: "<<ct<<endl;
}

//des-decrypt
// Including dependancies
#include <iostream>
#include <string>
#include <cmath>
using namespace std;
// Array to hold 16 keys
string round_keys[16];
// String to hold the plain text
string pt;
// Function to convert a number in decimal to binary
string convertDecimalToBinary(int decimal)
{
    string binary;
    while(decimal != 0) {
        binary = (decimal % 2 == 0 ? "0" : "1") + binary; 
        decimal = decimal/2;
    }
    while(binary.length() < 4){
        binary = "0" + binary;
    }
    return binary;
}
// Function to convert a number in binary to decimal
int convertBinaryToDecimal(string binary)
{
    int decimal = 0;
    int counter = 0;
    int size = binary.length();
    for(int i = size-1; i >= 0; i--)
    {
        if(binary[i] == '1'){
            decimal += pow(2, counter);
        }
    counter++;
    }
    return decimal;
}
// Function to do a circular left shift by 1
string shift_left_once(string key_chunk){ 
    string shifted="";  
        for(int i = 1; i < 28; i++){ 
            shifted += key_chunk[i]; 
        } 
        shifted += key_chunk[0];   
    return shifted; 
} 
// Function to do a circular left shift by 2
string shift_left_twice(string key_chunk){ 
    string shifted=""; 
    for(int i = 0; i < 2; i++){ 
        for(int j = 1; j < 28; j++){ 
            shifted += key_chunk[j]; 
        } 
        shifted += key_chunk[0]; 
        key_chunk= shifted; 
        shifted =""; 
    } 
    return key_chunk; 
}
// Function to compute xor between two strings
string Xor(string a, string b){ 
    string result = ""; 
    int size = b.size();
    for(int i = 0; i < size; i++){ 
        if(a[i] != b[i]){ 
            result += "1"; 
        }
        else{ 
            result += "0"; 
        } 
    } 
    return result; 
} 
// Function to generate the 16 keys.
void generate_keys(string key){
    // The PC1 table
    int pc1[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 
    };
    // The PC2 table
    int pc2[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 
    }; 
    // 1. Compressing the key using the PC1 table
    string perm_key =""; 
    for(int i = 0; i < 56; i++){ 
        perm_key+= key[pc1[i]-1]; 
    } 
    // 2. Dividing the key into two equal halves
    string left= perm_key.substr(0, 28); 
    string right= perm_key.substr(28, 28); 
    for(int i=0; i<16; i++){ 
        // 3.1. For rounds 1, 2, 9, 16 the key_chunks
        // are shifted by one.
        if(i == 0 || i == 1 || i==8 || i==15 ){
            left= shift_left_once(left); 
            right= shift_left_once(right);
        } 
        // 3.2. For other rounds, the key_chunks
        // are shifted by two
        else{
            left= shift_left_twice(left); 
            right= shift_left_twice(right);
        }
        // Combining the two chunks
        string combined_key = left + right;
        string round_key = ""; 
        // Finally, using the PC2 table to transpose the key bits
        for(int i = 0; i < 48; i++){ 
            round_key += combined_key[pc2[i]-1]; 
        }   
        round_keys[i] = round_key; 
    } 

}
// Implementing the algorithm
string DES(){ 
    // The initial permutation table 
    int initial_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 
    }; 
    // The expansion table
    int expansion_table[48] = { 
    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 
    }; 
    // The substitution boxes. The should contain values
    // from 0 to 15 in any order.
    int substition_boxes[8][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 }
    }, 
    { 
    {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 }
    }};
    // The permutation table
    int permutation_tab[32] = { 
    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 
    }; 
    // The inverse permutation table
    int inverse_permutation[64]= { 
    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 
    };
    //1. Applying the initial permutation
    string perm = ""; 
    for(int i = 0; i < 64; i++){ 
        perm += pt[initial_permutation[i]-1]; 
    }  
    // 2. Dividing the result into two equal halves 
    string left = perm.substr(0, 32); 
    string right = perm.substr(32, 32);
    // The plain text is encrypted 16 times  
    for(int i=0; i<16; i++) { 
        string right_expanded = ""; 
        // 3.1. The right half of the plain text is expanded
        for(int i = 0; i < 48; i++) { 
            right_expanded += right[expansion_table[i]-1]; 
    };  // 3.3. The result is xored with a key
        string xored = Xor(round_keys[i], right_expanded);  
        string res = ""; 
        // 3.4. The result is divided into 8 equal parts and passed 
        // through 8 substitution boxes. After passing through a 
        // substituion box, each box is reduces from 6 to 4 bits.
        for(int i=0;i<8; i++){ 
            // Finding row and column indices to lookup the
            // substituition box
            string row1= xored.substr(i*6,1) + xored.substr(i*6 + 5,1);
            int row = convertBinaryToDecimal(row1);
            string col1 = xored.substr(i*6 + 1,1) + xored.substr(i*6 + 2,1) + xored.substr(i*6 + 3,1) + xored.substr(i*6 + 4,1);;
            int col = convertBinaryToDecimal(col1);
            int val = substition_boxes[i][row][col];
            res += convertDecimalToBinary(val);  
        } 
        // 3.5. Another permutation is applied
        string perm2 =""; 
        for(int i = 0; i < 32; i++){ 
            perm2 += res[permutation_tab[i]-1]; 
        }
        // 3.6. The result is xored with the left half
        xored = Xor(perm2, left);
        // 3.7. The left and the right parts of the plain text are swapped 
        left = xored; 
        if(i < 15){ 
            string temp = right;
            right = xored;
            left = temp;
        } 
    } 
    // 4. The halves of the plain text are applied
    string combined_text = left + right;   
    string ciphertext =""; 
    // The inverse of the initial permuttaion is applied
    for(int i = 0; i < 64; i++){ 
        ciphertext+= combined_text[inverse_permutation[i]-1]; 
    }
    //And we finally get the cipher text
    return ciphertext; 
}
int main(){ 
    // A 64 bit key
    // string key= "0001001100110100010101110111100110011011101111001101111111110001";
    string key;
    cout << "Enter the 64-bit key : ";
    getline(cin, key);

    // A block of plain text of 64 bits
    // pt= "0000000100100011010001010110011110001001101010111100110111101111";
    cout << "Enter the 64-bit plain text : ";
    getline(cin, pt);
    
    string apt = pt;
    // Calling the function to generate 16 keys
    generate_keys(key); 
    cout<<"Plain text: "<<pt<<endl; 
    // Applying the algo
    string ct= DES(); 
    cout<<"Ciphertext: "<<ct<<endl;
    // Reversing the round_keys array for decryption
    int i = 15;
    int j = 0;
    while(i > j)
    {
        string temp = round_keys[i];
        round_keys[i] = round_keys[j];
        round_keys[j] = temp;
        i--;
        j++;
    }
    pt = ct;
    string decrypted = DES();
    cout<<"Decrypted text:"<<decrypted<<endl;
    // Comapring the initial plain text with the decrypted text
    if (decrypted == apt){
        cout<<"Plain text encrypted and decrypted successfully."<<endl;
    }
}