C++ XOR encryption function to AutoIt

[Unc3nZureD]

I'd like to translate a piece of C++ code into AutoIt. Well,the C++ source is a CTRL+C & CTRL+V for me, I don't really know how it works, that's why I can't really translate it. Well, my huge fault, but still, this code would be really important for me!

So, it's a simple XOR encryption. Another problem is that I can't yet understand, how the hell it work (I mean wtf is this XOR)... Well, I'm trying to learn it, but meanwhile I post this topic. Here's the C++ source:

string encryptDecrypt(string toEncrypt)
{
    char key[16] = { 'x', 'Y', 'b', 'N', 'k', 'k', 'F', 'X', 'x', ']', 's', 't', 'o', 'a', 'V', 'c' };
    string output = toEncrypt;

    for (int i = 0; i < toEncrypt.size(); i++)
        output[i] = toEncrypt[i] ^ key[i % (sizeof(key) / sizeof(char))];

    return output;
}

Well, for loop is clear, I have to XOR each letter with a key. But what Is the key? I mean there's an array, but what the hell is this:

i % (sizeof(key) / sizeof(char))

I hope you gus can help me. Thanks a lot!

( I know it isn't that good not to provide an autoit code which I've written, but anyone can write a for loop, it's not that big deal, and what I don't know is the hearth of the code )

[BrewManNH]

XOR = Exclusive Or

http://en.wikipedia.org/wiki/Xor

[Unc3nZureD]

Yes, I can use google too I can understand how to XOR for example two unions in maths, but I still get mindf*ck when reading that wiki post

Could you help me how to translate that

toEncrypt[i] ^ key[i % (sizeof(key) / sizeof(char))];

part? I have to XOR each letter with the key. But what is the key?

[BrewManNH]

Looks like the key is the key array, you're stepping through the array one element at a time, and stepping through the string on character at a time. Then XORing the string with the array value.

BTW, there's a BitXOr function that might help in this.

[Unc3nZureD]

Yes, I've seen the BitXOR command, I just wasn't sure what's the key. So you mean that I XOR each character the following way:

1st char: Key 1st letter (x)

2nd char: Key 2nd letter (Y)

...

...

16th char: Key 16th letter ( c )

17th char: Key 1st letter again (x)

...

...

Edited April 8, 2014 by Unc3nZureD

[BrewManNH]

From what you posted that's what I'm guessing. I'm not all that good with C/C++ either so I'm going on limited knowledge, but it appears to work that way.

[Unc3nZureD]

I made this little script:

#include <Array.au3>

$text = FileRead(@ScriptDir & "\log.txt")
$text = "Welcome to my little world!"

$arr = StringSplit($text, "", 2)
$key = StringSplit('BzWul]ISL[SWXHvd', "", 2)

$keyindex = 0
For $i = 0 To UBound($arr) - 1
    $keyindex += 1
    If $keyindex = UBound($key) Then
        $keyindex = 0
    EndIf

    $arr[$i] = BitXOR($arr[$i], $key[$keyindex])
Next

$b = _ArrayToString($arr, "")
MsgBox(0,"", $b, "Decoded:")
ClipPut($b)

The originally encrypted text, which should be decrypted is in the log.txt, but it isn't working, so I tried to set a simple text if it works. I have to say no. Any idea what could be the problem? It returns: 000000000000000000000000000

I tried to replace the BitXOR with this:

$arr[$i] = $arr[$i] ^ $key[$keyindex]

But it returns the same, except that all of them are 111111...

What did I miss?

_________________________________________________

As I see, I can XOR only HEX stuffs. How come c++ is able to XOR it meanwhile it's still char? Does it auto converts it? Anyways I still couldn't write a working function :/

Edited April 8, 2014 by Unc3nZureD

[Unc3nZureD]

Woooohooo I've finished it More or less I understand it now Here's my code if anyone needs it:

#include <Array.au3>
$key = "AnyKeyIsWrittenHere"
$xor = XOREncrypt("Welcome to my little world!", $key)
$dexor = XOREncrypt($xor, $key)

MsgBox(0,"", $xor, "Decoded:")
MsgBox(0,"", $dexor, "Decoded:")
ClipPut($xor)

Func XOREncrypt($data, $key)
    $arr = StringSplit($data, "", 2)
    $key = StringSplit($key, "", 2)

    ArrayToHex($arr)
    ArrayToHex($key)

    $keyindex = 0
    For $i = 0 To UBound($arr) - 1
        $keyindex += 1
        If $keyindex = UBound($key) Then
            $keyindex = 0
        EndIf

        $arr[$i] = Hex( BitXOR($arr[$i], $key[$keyindex]), 2 )
    Next

    return BinaryToString("0x" & _ArrayToString($arr, ""))
EndFunc

Func ArrayToHex(ByRef $array)
    For $i = 0 to UBound($array) - 1
        $array[$i] = StringToBinary($array[$i])
    Next
EndFunc

(ArrayToHex is just a small helping function)

___________________________________________________________________

Edit:

Well, it took some hours to understand how it works Well, the only thing is that it won't decrypt the code I've got in C++.

I attached a sample if anyone needs it. It has been encrypted with the following char array: BzWul]ISL[sWXHvd

What did I miss again?

log.txt

Edited April 8, 2014 by Unc3nZureD

[Unc3nZureD]

1st: BUMP

2nd: I looked thru the c++ code again. I rechecked the following string

output[i] = toEncrypt[i] ^ key[i % (sizeof(key) / sizeof(char))];

This one encrypts the char with the key. It make the following thing in autoit, if I'm right:

key[i % (sizeof(key) / sizeof(char))]

   |

  /

$key[Mod($i, 16)] ; 16, because sizeof(key) might be 16, and If I'm right sizeof(char) is 1.

Could anyone confirm me? Just because it's not working too...

$arr[$i] = Hex( BitXOR($arr[$i], $key[Mod($i, 16)]), 2 )

[jchd]

This is how I would code it:

Local $sPlaintext = "I'd like to translate a piece of C++ code into AutoIt. Well,the C++ source is a CTRL+C & CTRL+V for me, I don't really know how it works, that's why I can't really translate it. Well, my huge fault, but still, this code would be really important for me!" & @CRLF & _
"So, it's a simple XOR encryption. Another problem is that I can't yet understand, how the hell it work (I mean wtf is this XOR)... Well, I'm trying to learn it, but meanwhile I post this topic. Here's the C++ source:"

Global $sPad = "Could anyone confirm me? Just because it's not working too..."

Local $sCiphertext = _Vernam($sPlaintext)
ConsoleWrite("Ciphertext: " &  Binary($sCiphertext) & @LF & @LF)
ConsoleWrite("Recovered plaintext: " & _Vernam($sCiphertext) & @LF)

Func _Vernam($sIn)
    Local $aIn = StringToASCIIArray($sIn)
    Local $aPad = StringToASCIIArray($sPad)
    Local $sOut
    For $i = 0 To UBound($aIn) - 1
        $sOut &= ChrW(BitXOR($aIn[$i], $aPad[Mod($i, UBound($aPad))]))
    Next
    Return $sOut
EndFunc

Anyway, keep in mind that your key definitely needs to be at least as long as the plaintext, must be used only once and needs to have pretty good randomness. All criterions that this toy example misses. Forget any condition and you're going to be severely bitten.