<?php
/**
* gEncrypter - PHP Class to encrypt and decrypt datas using a given key
*
* Tested and working on PHP 4.3.2 and higher
*
* LICENSE: This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License v2 as published by
* the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* @author Giulio Bai <slide.wow@gmail.com>
* @copyright (C)2007 Giulio Bai
* @license http://www.gnu.org/licenses/gpl.html GNU General Public License
* @version 1.0
* @link http://hewle.com
*/
/**
* Ecrypts and decrypts text using a user-provided key to create a new alphabet.
* To get the original text the key is needed again and, if the keys match,
* the original text is given back.
*
* I haven't understood why, but certain characters (§, °, £, è, é, ò, à , ù, ç)
* can not be used and converted because it will return a blank space. However
* I tested all the others chars and letters (both lowercase and uppercase) and
* I found it works, converting text (and files too!) and then recreating the
* original given entry.
*
* @author Giulio Bai <slide.wow@gmail.com>
* @copyright (C)2007 Giulio Bai
* @license http://www.gnu.org/licenses/gpl.html GNU General Public License
* @version 1.0
* @link http://hewle.com
*/
class gEncrypter
{
/**
* Key needed by the methods to encrypt and decrypt documents
*
* @var string
*/
var $key;
/**
* Creates a new alphabet depending on the key provided.
*
* The process is something like the following:
* Consider the key $key = "ilarvet"
*
* The program creates an array using as indexes the chars of the key and
* assigns to them the first letters of the alphabet, without any double char
*
* So the conv array will be
* $conv = array(
* "i" => "b",
* "l" => "c",
* "a" => "d",
* "r" => "f",
* "v" => "g",
* "e" => "h",
* "t" => "j"
* );
*
* Then sobstitutes corresponding letters looking up for them into the conv array
* a b c d e f g h i j k l m n o p q r s t u v w x y z
* d ? ? ? h ? ? ? b ? ? c ? ? ? ? ? f ? j ? g ? ? ? ?
*
* Assigns the already-known chars
* a b c d e f g h i j k l m n o p q r s t u v w x y z
* d i l a h r v e b t ? c ? ? ? ? ? f ? j ? g ? ? ? ?
*
* Assigns to each letter its opposite in the sequence, avoiding already
* assigned chars
* a b c d e f g h i j k l m n o p q r s t u v w x y z
* d i l a h r v e b t z c y x w u s f q j p g o n m k
*
* We now have a new alphabet!
*
* @return mixed the array of the new alphabet
*/
function gMA()
{
$key = $this->key;
$a = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
'W', 'X', 'Y', 'Z', '1', '2', '3', '4', '5', '6', '7', '8',
'9', '0', ',', '.', ';', ':', '-', '_', '!', '$', '%', '&',
'/','(', ')', '=', '?', '^', '*', '+', '[', ']', '{', '}',
'<', '>', '|', '\\', '\'', '"', ' '
);
// array of key's chars
$key_array = array();
// key conversion array
$conv = array();
// new alphabet
$new_a = array();
// not assigned chars
$na = array();
// Creates the key array
for ($i=0; $i<strlen($key); $i++) {
$char = substr($key, $i, 1);
if (!in_array($char, $key_array)) {
$key_array[$i] = $char;
} else
die("Check your key syntax!");
}
// converts the letters already known in the new alphabet
for ($i=0; $i<count($a); $i++)
$new_a[$a[$i]] = $a[$i];
// print_r($new_a);
$count = 0;
// Back assignement in the new alpabet and filling the conv array
for ($i=0; $i<strlen($key); $i++) {
$char = substr($key, $i, 1);
while (in_array($a[$count], $conv) || in_array($a[$count], $key_array))
$count ++;
$conv[$char] = $a[$count];
$new_a[$char] = $conv[$char];
for ($k=0; $k<count($a); $k++)
$new_a[$new_a[$a[$k]]] = $a[$k];
}
// Fills in the notassigned array
for ($i=0; $i<count($a); $i++) {
if ($new_a[$a[$i]] == $a[$i])
$na[] = $a[$i];
}
$c = count($na);
/**
* Alphabet inversion process
*
* 1. take a letter
* 2. has it changed from the original alphabet?
* YES -> 3. next letter
* ---> 2
* NO -> 4. take the opposite letter in the original alphabet
* 5. is it already assigned to another letter?
* YES -> 6. take the letter immediately before
* ---> 5
* NO -> assign to the first letter taken the free letter
* ---> 3
*/
for ($i=0; $i<count($new_a); $i++) {
if ($new_a[$a[$i]] == $a[$i]) {
$new_a[$a[$i]] = $na[$c-1];
$c --;
}
}
return $new_a;
}
/**
* Encrypts or decrypts datas depending on a certain key
*
* Makes a new alphabet depending on the key provided then replaces each char
* in the text with its corresponding in the new alphabet.
*
* Please NOTE this function encrypts AND decrypts; this mean if the text
* passed to it is already encrypted using this system and the same key, it
* will return the original one, else it will return a text encrypted two
* times using two DIFFERENT keys and you'll need two decryption to get the
* original text back.
*
* If the text passed to the method isn't ecnrypted yet, it will return the
* text encrypted once. The same thing happens if you use a key which match
* the sequence of the original alphabet.
*
* @param string $string the text to encrypt/decrypts
* @param string $key the string to use to encrypt/decrypt
* @return string the string encrypted/decrypted
*/
function gED($string, $key)
{
$this->key = $key;
$new_a = $this->gMA();
$enc = "";
// Creating the new text
for ($i=0; $i<strlen($string); $i++) {
$cs = substr($string, $i, 1);
// if ($cs == " ")
// $enc .= " ";
// else {
$cs = $new_a[$cs];
$enc .= $cs;
// }
}
// print_r($new_a);
return $enc;
}
}
?>
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