Encryption System Problem

Cagri · July 20, 2009

Hi,

I wrote an simple encryption system. There is a simple mathematical process multiplication and division. But it's not workin correctly. What's wrong i can not understand. Please help me. I just want to fix this problem please don't offer me alternative methods for encryption.

Thanks.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>Encryption System</title><body>

<form action ="<?php $_SERVER['PHP_SELF']; ?>"method ="POST"><h1 align="center">Encryption System</h1>

<p align="center"><input name="radio1" type="radio" value ="encode" checked="checked">Encode <input name="radio1" type="radio" value = "decode">Decode</p>

<?php

$selected_radio = $_POST[radio1];

$text = $_POST['encryption'];

function encrypt($text) {

Global $crypto;

ini_set ( 'precision', 131087 );

$search = range ( chr ( 1 ), chr ( 255 ) );

foreach ( range ( 1, 255 ) as $num )

$replace [] = str_pad($num,3,0,STR_PAD_LEFT);

$crypto = strtr ( $text, array_combine ( $search, $replace ) ) ;

$key = '67285789764983209584182738495874734473673467368232293248932298313131081291108578560185780

348549838461465813437569857428502758027';

$crypto = ($crypto * $key);

//return base64_encode($crypto);

return floatval($crypto);

}

function decrypt($text) {

Global $crypto;

ini_set ( 'precision', 131087 );

$key = '67285789764983209584182738495874734473673467368232293248932298313131081291108578560185780

348549838461465813437569857428502758027';

$text = ($text / $key);

$search = range ( chr ( 1 ), chr ( 255 ) );

foreach ( range ( 1, 255 ) as $num )

$replace [] = str_pad($num,3,0,STR_PAD_LEFT);

//$string = base64_decode($string);

$crypto = strtr ( $text, array_combine ( $replace, $search ) ) ;

return ($crypto);

}

encrypt($text);

if ($selected_radio == 'encode') { echo $crypto;}

decrypt($text);

if ($selected_radio == 'decode') { echo $crypto;

}

?></textarea>

</body>

</html>

ignace · July 20, 2009

$key = '67285789764983209584182738495874734473673467368232293248932298313131081291108578560185780
348549838461465813437569857428502758027';
$crypto = ($crypto * $key);

This may be your problem if you multiply $key it is transformed to an integer (not entirely, explained later). A computer uses the 2-complement system and when it exceeds 2^32 (4 billion, unsigned integer) It continues in the negative part (-2^16). So when php parses $key it will use it's biggest possible type it has and assign $key that type and everything he can't fit into it is cut off. Use PHP_INT_MAX instead.

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