/* Lucas, Aug 26, 2019 Caesar Cipher to encrypt: In: e 6 Lucas Out: Raigy to decrypt: In: d 6 Raigy Out: Lucas */ // CaesarCore.h #ifndef CAESAR_CORE_H #define CAESAR_CORE_H #include class CaesarCore { public: static std::string cipher(std::string& message, int key, bool encOrDec); private: static char _shifChar(int key, int c, bool encOrdec); }; #endif // !CAESAR_CORE_H // CaesarCore.cc #include //#include "CaesarCore.h" int _euclideanMod(int a, int b) { int mod = a % b; if (mod < 0) mod = (b < 0) ? mod - b : mod + b; return mod; } std::string CaesarCore::cipher(std::string& message, int key, bool encOrDec) { std::string enMsg = ""; for (char& c : message) { char temp = _shifChar(key, c, encOrDec); enMsg += temp; } return enMsg; } char CaesarCore::_shifChar(int key, int c, bool encOrdec) { std::string alpArr = "abcdefghijklmnopqrstuvwxyz"; int eC = c; bool isUpper = std::isupper(eC); if (isUpper) { eC += 32; } int index = alpArr.find(eC); if (index != std::string::npos) { if (encOrdec) { eC = alpArr[(index + key) % 26]; } else { eC = alpArr[_euclideanMod((index - key), 26)]; } } if (isUpper) { eC -= 32; } return static_cast(eC); } // main.cc #include #include //#include "CaesarCore.h" std::string input(const std::string prompt="") { std::string temp; std::cout << prompt; std::getline(std::cin, temp); return temp; } int main(int argc, char* argv[]) { std::string choice = []() { std::string temp = ""; do { temp = input("\"e\" for encryption OR \"d\" for decryption >>> "); if (temp[0] == 'd' || temp[0] == 'e') break; } while (1); return temp; }(); int key = []() { int i = 1; do { try { i = std::stoi(input("\nSecret key >>> ")); if (i >= 1 && i <= 26) break; } catch (...) { continue; } } while (1); return i; }(); std::string message = input("\nMessage >>> "); if (choice[0] == 'e') { std::cout << '\n' << CaesarCore::cipher(message, key, true); } else { std::cout << '\n' << CaesarCore::cipher(message, key, false); } return 0; }

Caesar Cipher | C++