[gameprogrammer] Re: XOR Problem

On Sun, 6 May 2007 16:36:34 -0300, "Edilson Vasconcelos de Melo Junior"
<dirso@xxxxxxxxxxxxxxxxxx> said:
>             for (string::iterator i = Text.begin(); i != Text.end(); i++)
> 
>             {
> 
>                   letter = code | *i;

Shouldn't this line be:

letter = code ^ *i;

You still want to xor it to get it back to its original state, that's
the whole point.

Have a look at the attached one for a cleaned up version of your code.

Dave.
-- 
  Dave Slutzkin
  Melbourne, Australia
  daveslutzkin@xxxxxxxxxxx


#include <iostream>
#include <string>

using namespace std;

string
encrypt(
        const string& password,
        const string& plainText)
{
    unsigned short int code = 0;
    for (string::const_iterator i = password.begin(), end = password.end();
         i != end; ++i)
    {
        code ^= *i;
    }

    string encrypted_text;
    for (string::const_iterator i = plainText.begin(), end = plainText.end();
         i != end; ++i)
    {
        const unsigned short int plain_letter = *i;
        const unsigned short int encrypted_letter = plain_letter ^ code;

        encrypted_text.push_back(encrypted_letter);

        code ^= plain_letter;
    }

    return encrypted_text;
}

string
decrypt(
        const string& password,
        const string& encryptedText)
{
    unsigned short int code = 0;
    for (string::const_iterator i = password.begin(), end = password.end();
         i != end; ++i)
    {
        code ^= *i;
    }

    string plain_text;
    for (string::const_iterator i = encryptedText.begin(),
         end = encryptedText.end(); i != end; ++i)
    {
        const unsigned short int encrypted_letter = *i;
        const unsigned short int plain_letter = code ^ encrypted_letter;

        plain_text.push_back(plain_letter);

        code ^= plain_letter;
    }

    return plain_text;
}

int
main(int argc, char* argv[])
{
    string s1 = "Teste do Xor do Dirso";
    cout << "s1: " << s1 << endl;

    string s2 = encrypt("OK", s1);
    cout << "s2: " << s2 << endl;

    string s3 = decrypt("OK", s2);
    cout << "s3: " << s3 << endl;

    return 0;
}

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