The encryption and decryption for the Substitution is not working please fix that. #include #include using namespace std; class Cipher { public: virtual string encode() = 0; virtual string decode() = 0; }; class SubstitutionCipher : Cipher { // int key; string key; string input; // static string _encode(string input, int key); string _getValidKey(); static bool isKeyValid(string key); public: //constructor SubstitutionCipher(string msg, string k) { this->input = msg; if (isKeyValid(k)) { this->key = k; } else { this->key = _getValidKey(); } } //the function for encryption/decryption (CaesarCipher algorithm) string encode(); string decode(); }; class CaesarCipher : Cipher { int key; string input; static string _encode(string input, int key); public: //constructor CaesarCipher(string msg, int k) : input(msg), key(k) {} //the function for encryption/decryption (CaesarCipher algorithm) string encode(); string decode(); }; /////////////////////////////////////////////////////////////////////// //the function for encryption/decryption (Substitution algorithm) // Encryption bool SubstitutionCipher::isKeyValid(string key) { if (key.length() != 26) { return false; } const int ARRAY_SIZE = 255; bool *arr = new bool[ARRAY_SIZE]; for (int i = 0; i < ARRAY_SIZE; i++) { arr[i] = false; } for (auto character : key) { if (arr[character] == true || tolower(character) < 97 || toupper(character) > 122) { delete arr; return false; } } return true; } string SubstitutionCipher::_getValidKey() { string key; cout << "Enter key: "; getline(cin, key); if (isKeyValid(key)) { return key; } return SubstitutionCipher::_getValidKey(); } string SubstitutionCipher::encode() { char ch; string output(input.length(), '\0'); for (int i = 0; i < input.length(); i++) { ch = tolower(input[i]); if (ch < 97 || ch > 122) { output[i] = ch; } else { output[i] = key[ch - 97]; } } return output; } string SubstitutionCipher::decode() { char ch; string output(input.length(), '\0'); for (int i = 0; i < input.length(); i++) { ch = tolower(input[i]); if (ch < 97 || ch > 122) { output[i] = ch; } else { int index = key.find(ch); output[i] = 'a' + index; // output[i] = key[ch - 97]; } } return output; } /////////////////////////////////////////////////////////////////////// //the function for encryption/decryption (CaesarCipher algorithm) string CaesarCipher::_encode(string input, int key) { string output = ""; for (int i = 0; i < input.size(); ++i) { if (isalpha(input[i])) //if letter { //offset='A' for upper letter, offset='a' for lowel letter char offset = isupper(input[i]) ? 'A' : 'a'; //convert letter (shift letter) char ch = (char)(((input[i] + key - offset) % 26) + offset); output += ch; } else { //non letter output += input[i]; } } return output; } string CaesarCipher::encode() { return CaesarCipher::_encode(this->input, this->key % 26); } string CaesarCipher::decode() { return CaesarCipher::_encode(this->input, 26 - (this->key % 26)); } /////////////////////////////////////////////////////////////////////// int main() { /* Encrypt a string entered by the user Choose between two different encryption methods Decrypt a string entered by the user Choose between two different decryptions methods Decrypt without knowing the encryption method (provide all possible outputs) */ string source = ""; int option; int caesarKey; string substitutionKey; do { cout << "\nEnter the text>> " << flush; getline(cin, source); cin.ignore(); // cin.ignore(256, '\n'); cout << "Make your choice" << endl; cout << "\t1. Mono-alphabetic substitution cipher, encrypt" << endl; cout << "\t2. Mono-alphabetic substitution cipher, decrypt" << endl; cout << "\t3. Caesar cipher, encrypt" << endl; cout << "\t4. Caesar cipher, decrypt" << endl; cout << "\t5. Decrypt without knowing the encryption method (provide all possible outputs)" << endl; cout << "\t6. Exit" << endl; cout << ">> "; cin >> option; cin.ignore(); string result; switch (option) { case 1: { cout << "Enter key for substitution cipher: "; getline(cin, substitutionKey); cin.ignore(); SubstitutionCipher s(source, substitutionKey); result = s.encode(); cout << endl << "The encryption string:\n" << result << "\n"; break; } case 2: { cout << "Enter key for substitution cipher: "; getline(cin, substitutionKey); cin.ignore(); SubstitutionCipher s(source, substitutionKey); result = s.decode(); cout << endl << "The decryption string:\n" << result << "\n"; break; } case 3: { cout << "Enter key for caesar cipher: "; cin >> caesarKey; cin.ignore(); CaesarCipher t(source, caesarKey); result = t.encode(); cout << endl << "The encryption string:\n" << result << "\n"; break; } case 4: { cout << "Enter key for caesar cipher: "; cin >> caesarKey; cin.ignore(); CaesarCipher t(source, caesarKey); result = t.decode(); cout << endl << "The decryption string:\n" << result << "\n"; break; } case 5: { cout << "All permutations using Caesar cipher" << endl; for (int i = 0; i < 25; i++) { CaesarCipher t(source, i); result = t.decode(); cout << result << endl; } // You can try all permutations of the string "abcdefghijklmnopqrstuvwxyz" // for the mono-alphabetic substitution cipher break; } case 6: cout << endl << "Goodbye!" << endl; break; } } while (option != 6); return 0; }