encryption from char to int - c++

Question

i'am writing some encryption program in c++, and when i start it then console print only one char, and decryption don't work, when i do encryption / decryption then program not doing that with numeric numbers of nn, he do that with hes adress. sorry for my english.
// Var
std::string text = "string";
const char *nn = text.c_str();
// Encryption
int x = (int(nn));
x = x * 3 - 100 * 2;
cout << "Numerical numbers: " << x << endl;
cout << "String: " << (char(x)) << endl;
// Decryption
x = (x - 100 * 2) / 3;
cout << "Numerical numbers: " << x << endl;
cout << "String: " << (char(x));

Answer 1

I suppose you would like to encrypt every characters of this:
std::string text = "string";
In this case you will need a vector of integers instead of a single int, to store every encoded character:
std::vector<int> encrypted;
Since you know what will be the final size of the vector, you can prepare the vector beforehand to allocate the necessary space, but this is optional:
encrypted.reserve(text.size());
Than you have to go through the characters one by one, encode them and put them to the vector:
for(auto &ch : text) {
int x = ch * 3 - 100 * 2;
encrypted.push_back(x);
}
The resulting vector can be printed this way:
cout << "Numerical numbers: ";
for(auto x : encrypted) { cout << x << ", "; }
cout << endl;
The decryption is analogous:
std::string decrypted;
decrypted.reserve(encrypted.size());
for(auto &x : encrypted) {
char ch = (x + 100 * 2) / 3;
decrypted += ch;
}

Answer 2

Unless you have restrictions that you have to use the formula x * 3 - 100 * 2 for encryption/decryption, I suggest you to use XOR.
#include <iostream>
#include <string>
int main()
{
// Var
std::string text = "string", encrypt, decrypt;
// Encryption
for (int i = 0; i < text.length(); i++)
{
encrypt += text[i] ^ '1';
}
// Decryption
for (int i = 0; i < encrypt.length(); i++)
{
decrypt += encrypt[i] ^ '1';
}
std::cout << "original text: " << text << std::endl << "encrypted text: " << encrypt << std::endl << "decrypted text: " << decrypt;
}
The output of the above code would be:
original text: string
encrypted text: BECX_V
decrypted text: string
Here is an working example of the above code.