C++ Vigenere and Caesar cipher in the same programming with switch case - c++

Question

In the first code I did a Caesar cipher and it is working well. However, i cannot added Vigenere. There is a class and some pointers, but they do not work in the switch-case statement, so I need help.
encryption part is switch case :3
decryption part is switch case :4
#include <iostream>
#include <string.h>
#include <string>
using namespace std;
char message[200], ch;
int i, key;
string k,output,messageV;
int menu(int answer);
int main()
{
int answer;
bool keepLooping = true;
while (keepLooping)
{
cout << "Pick a Choice from the List: \n(1)Caesar \n(2)Vigenere \n ";
cin >> answer;
if (answer == 1)
{
while(keepLooping)
{
cout << "Pick a Choice from the List: \n(1)Encryption\n(2)Decryption \n ";
cin >> answer;
if (answer == 1)
{
answer = 1;
keepLooping = false ;
}
else if(answer == 2)
{
answer = 2;
keepLooping = false;
}
else
{
keepLooping = true;
}
}
}
else if(answer == 2)
{
while(keepLooping)
{
cout << "Pick a Choice from the List: \n(1)Encryption\n(2)Decryption \n ";
cin >> answer;
if (answer == 1)
{
answer = 3;
keepLooping = false ;
}
else if(answer == 2)
{
answer = 4;
keepLooping = false;
}
else
{
keepLooping = true;
}
}
}
else
{
keepLooping = true;
}
}
menu(answer);
}
int menu(int answer)
{
switch (answer)
{
case 1://Caesar Cipher Encryption
cout << "Enter a message to encrypt: ";
cin.ignore();
cin.getline(message, 200);
cout << "Enter key: ";
cin >> key;
for(i = 0; message[i] != '\0'; ++i){
ch = message[i];
if(ch >= 'a' && ch <= 'z'){
ch = ch + key;
if(ch > 'z'){
ch = ch - 'z' + 'a' - 1;
}
message[i] = ch;
}
else if(ch >= 'A' && ch <= 'Z'){
ch = ch + key;
if(ch > 'Z'){
ch = ch - 'Z' + 'A' - 1;
}
message[i] = ch;
}
}
cout << "Encrypted message: " << message;
break;
case 2://Caesar Cipher Decryption
cout << "Enter a message to decrypt: ";
cin.ignore();
cin.getline(message, 200);
cout << "Enter key: ";
cin >> key;
for(i = 0; message[i] != '\0'; ++i){
ch = message[i];
if(ch >= 'a' && ch <= 'z'){
ch = ch - key;
if(ch < 'a'){
ch = ch + 'z' - 'a' + 1;
}
message[i] = ch;
}
else if(ch >= 'A' && ch <= 'Z'){
ch = ch - key;
if(ch > 'a'){
ch = ch + 'Z' - 'A' + 1;
}
message[i] = ch;
}
}
cout << "Decrypted message: " << message;
break;
case 3:
cout << "CASE 3";
break;
case 4:
cout << "CASE 4";
break;
default:
cout << "There is no choices." << endl;
}
return answer;
}
Vigenere part:
#include <iostream>
#include <string>
using namespace std;
class Vig {
public:
string k;
Vig(string k) {
for (int i = 0; i < k.size(); ++i) {
if (k[i] >= 'A' && k[i] <= 'Z')
this->k += k[i];
else if (k[i] >= 'a' && k[i] <= 'z')
this->k += k[i] + 'A' - 'a';
}
}
string encryption(string t) {
string output;
for (int i = 0, j = 0; i < t.length(); ++i) {
char c = t[i];
if (c >= 'a' && c <= 'z')
c += 'A' - 'a';
else if (c < 'A' || c > 'Z')
continue;
output += (c + k[j] - 2 * 'A') % 26 + 'A'; //added 'A' to bring it in range of ASCII alphabet [ 65-90 | A-Z ]
j = (j + 1) % k.length();
}
return output;
}
string decryption(string t) {
string output;
for (int i = 0, j = 0; i < t.length(); ++i) {
char c = t[i];
if (c >= 'a' && c <= 'z')
c += 'A' - 'a';
else if (c < 'A' || c > 'Z')
continue;
output += (c - k[j] + 26) % 26 + 'A';//added 'A' to bring it in range of ASCII alphabet [ 65-90 | A-Z ]
j = (j + 1) % k.length();
}
return output;
}
};
int main() {
char message[200];
string key;
cout << "Key: ";
cin >> key;
cin.ignore();
Vig v(key);
cout << "Enter a message to encrypt: ";
cin.getline(message, 200);
string ori = message;
string encrypt = v.encryption(ori);
string decrypt = v.decryption(encrypt);
cout << "Original Message: "<<ori<< endl;
cout << "Encrypted Message: " << encrypt << endl;
cout << "Decrypted Message: " << decrypt << endl;
}

Answer 1

My suggestion is that you try to find the common patterns in your two programs. For example you have you have to methods to encrypt and decrypt. That could be abstracted into two different classes, perhaps with a common base-class defining the interface (allowing things like polymorphism):
struct Cipher
{
virtual std::string encryption(std::string const&) = 0;
virtual std::string decryption(std::string const&) = 0;
};
class Caesar : public Cipher
{
public:
std::string encryption(std::string const& s) override
{
// TODO: Implement Caesar cipher encryption
}
std::string decryption(std::string const& s) override
{
// TODO: Implement Caesar cipher decryption
}
};
class Vigenere : public Cipher
{
public:
std::string encryption(std::string const& s) override
{
// TODO: Implement Vigenere cipher encryption
}
std::string decryption(std::string const& s) override
{
// TODO: Implement Vigenere cipher decryption
}
};
From this we could create a set of functions to use any cipher (through pointers to the base Cipher class). Lets start with selecting which cipher to use:
Cipher* select_cipher()
{
std::cout << "Please select cipher to use:\n";
std::cout << "1) Caesar\n";
std::cout << "2) Vigenere\n";
int selection;
std::cin >> selection;
if (selection == 1)
{
return new Caesar;
}
else if (selection == 2)
{
return new Vigenere;
}
else
{
return nullptr;
}
}
Now we have a cipher to use, then select what to do:
int select_method()
{
std::cout << "Do you want to encrypt or decrypt?\n";
std::cout << "1) Encrypt\n";
std::cout << "2) Decrypt\n";
int method;
std::cin >> method;
return method;
}
Now we really have everything needed to use any supported cipher and method:
int main()
{
Cipher* cipher = select_cipher();
int method = select_method();
std::string input;
std::string result;
// TODO: Read input string to encrypt or decrypt
if (method == 1)
{
result = cipher->encryption(input);
}
else if (method == 2)
{
result = cipher->decryption(input);
}
std::cout << "Result = " << result << '\n';
}
Do note that this is only a very rough outline, and there are many parts missing (like the actual encryption and decryption algorithms). These are left as an exercise for the readers.
Instead of using if ... else if ... you can of course use switch. But for these simple cases it doesn't really matter, and if ... else if ... is, IMO, easier to read.

Answer 2

I coded it already can you check it too, please ?
#include <iostream>
#include <string>
using namespace std;
class Vig {
public:
string k;
Vig(string k) {
for (int i = 0; i < k.size(); ++i) {
if (k[i] >= 'A' && k[i] <= 'Z')
this->k += k[i];
else if (k[i] >= 'a' && k[i] <= 'z')
this->k += k[i] + 'A' - 'a';
}
}
string Vegencryption(string t) {
string output;
for (int i = 0, j = 0; i < t.length(); ++i) {
char c = t[i];
if (c >= 'a' && c <= 'z')
c += 'A' - 'a';
else if (c < 'A' || c > 'Z')
continue;
output += (c + k[j] - 2 * 'A') % 26 + 'A'; //added 'A' to bring it in range of ASCII alphabet [ 65-90 | A-Z ]
j = (j + 1) % k.length();
}
return output;
}
string Vegdecryption(string t) {
string output;
for (int i = 0, j = 0; i < t.length(); ++i) {
char c = t[i];
if (c >= 'a' && c <= 'z')
c += 'A' - 'a';
else if (c < 'A' || c > 'Z')
continue;
output += (c - k[j] + 26) % 26 + 'A';//added 'A' to bring it in range of ASCII alphabet [ 65-90 | A-Z ]
j = (j + 1) % k.length();
}
return output;
}
string Cesencryption(string t, int key){
string output;
char ch;
for(int i = 0; t[i] != '\0'; ++i){
ch = t[i];
if(ch >= 'a' && ch <= 'z'){
ch = ch + key;
if(ch > 'z'){
ch = ch - 'z' + 'a' - 1;
}
t[i] = ch;
}
else if(ch >= 'A' && ch <= 'Z'){
ch = ch + key;
if(ch > 'Z'){
ch = ch - 'Z' + 'A' - 1;
}
t[i] = ch;
}
}
output = t;
return output;
}
string Cesdencryption(string t, int key){
string output;
char ch;
for(int i = 0; t[i] != '\0'; ++i){
ch = t[i];
if(ch >= 'a' && ch <= 'z'){
ch = ch - key;
if(ch < 'a'){
ch = ch + 'z' - 'a' + 1;
}
t[i] = ch;
}
else if(ch >= 'A' && ch <= 'Z'){
ch = ch - key;
if(ch > 'a'){
ch = ch + 'Z' - 'A' + 1;
}
t[i] = ch;
}
}
output = t;
return output;
}
};
int main() {
char message[200];
string key;
int choice;
cout << "Pick a Choice from the List: \n(1)Caesar \n(2)Vigenere \n ";
cin >> choice;
if(choice == 2) //Vigenere
{
cout << "Pick a Choice from the List: \n(1)Encryption\n(2)Decryption \n ";
cin >> choice;
if (choice == 1)
{
cout << "Key: ";
cin >> key;
cin.ignore();
Vig v(key);
cout << "Enter a message to encrypt: ";
cin.getline(message, 200);
string ori = message;
string encrypt = v.Vegencryption(ori);
cout << "Encrypted Message: " << encrypt << endl;
}
else if (choice == 2)
{
cout << "Key: ";
cin >> key;
cin.ignore();
Vig v(key);
cout << "Enter a message to encrypt: ";
cin.getline(message, 200);
string ori = message;
string decrypt = v.Vegdecryption(ori);
cout << "Decrypted Message: " << decrypt << endl;
}
else
{
cout << "You Exit the Program.";
}
}
else if (choice == 1) //Ceaser
{
cout << "Pick a Choice from the List: \n(1)Encryption\n(2)Decryption \n ";
cin >> choice;
if (choice == 1)
{
int key;
cout << "Enter a message to encrypt: ";
cin.ignore();
cin.getline(message, 200);
cout << "Enter key: ";
cin >> key;
Vig v(message);
string ori = message;
string decrypt = v.Cesencryption(ori,key);
cout << "Decrypted Message: " << decrypt << endl;
}
else if (choice == 2)
{
int key;
cout << "Enter a message to dencrypt: ";
cin.ignore();
cin.getline(message, 200);
cout << "Enter key: ";
cin >> key;
Vig v(message);
string ori = message;
string encryption = v.Cesdencryption(ori,key);
cout << "Decrypted Message: " << encryption << endl;
}
else
{
cout << "You Exit the Program.";
}
}
else
{
cout << "You Exit the Program.";
}
}