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<?php
// ******************************************************************************
// A reversible password encryption routine by:
// Copyright 2003-2007 by A J Marston <http://www.tonymarston.net>
// Distributed under the GNU General Public Licence
// Modification: May 2007, M. Kolar <http://mkolar.org>:
// No need for repeating the first character of scramble strings at the end;
// instead using the exact inverse function transforming $num2 to $num1.
// ******************************************************************************

class encryption_class {

var $scramble1; // 1st string of ASCII characters
var $scramble2; // 2nd string of ASCII characters

var $errors; // array of error messages
var $adj; // 1st adjustment value (optional)
var $mod; // 2nd adjustment value (optional)

var $key_key;

// ****************************************************************************
// class constructor
// ****************************************************************************
function encryption_class ()
{
$this->errors = array();

// Each of these two strings must contain the same characters, but in a different order.
// Use only printable characters from the ASCII table.
// Do not use single quote, double quote or backslash as these have special meanings in PHP.
// Each character can only appear once in each string.
$this->scramble1 = '0_12345=6789ABC-DEFG/HIJKLMNOPQRS TUVWXYZabcde.fghijklmnopqrstuvwxy,z';
$this->scramble2 = 'f,/jAEokIOzU2q13h5w794p.6s8BgP dFVmDTc-SZerlGKuCyJ=xHiQLtRMaNvWYnb0_X';
$this->key_key = 'Spain_Champion_of_UEFA_Euro_2008';

if (strlen($this->scramble1) <> strlen($this->scramble2)) {
trigger_error('** SCRAMBLE1 is not same length as SCRAMBLE2 **', E_USER_ERROR);
} // if

$this->adj = 1.75; // this value is added to the rolling fudgefactors
$this->mod = 3; // if divisible by this the adjustment is made negative

} // constructor

// ****************************************************************************
function decrypt ($source) // ECG was here.
//function decrypt ($key, $source)
// decrypt string into its original form
{
$key = $this->key_key;
$this->errors = array();

// convert $key into a sequence of numbers
$fudgefactor = $this->_convertKey($key);
if ($this->errors) return;

if (empty($source)) {
$this->errors[] = 'No value has been supplied for decryption';
return;
} // if

$target = null;
$factor2 = 0;

for ($i = 0; $i < strlen($source); $i++) {
// extract a character from $source
$char2 = substr($source, $i, 1);

// identify its position in $scramble2
$num2 = strpos($this->scramble2, $char2);
if ($num2 === false) {
$this->errors[] = "Source string contains an invalid character ($char2)";
return;
} // if

// get an adjustment value using $fudgefactor
$adj = $this->_applyFudgeFactor($fudgefactor);

$factor1 = $factor2 + $adj; // accumulate in $factor1
$num1 = $num2 - round($factor1); // generate offset for $scramble1
$num1 = $this->_checkRange($num1); // check range
$factor2 = $factor1 + $num2; // accumulate in $factor2

// extract character from $scramble1
$char1 = substr($this->scramble1, $num1, 1);

// append to $target string
$target .= $char1;

//echo "char1=$char1, num1=$num1, adj= $adj, factor1= $factor1, num2=$num2, char2=$char2, factor2= $factor2<br />\n";

} // for

return rtrim($target);

} // decrypt

// ****************************************************************************
function encrypt ($source, $sourcelen = 0) // ECG was here.
//function encrypt ($key, $source, $sourcelen = 0)
// encrypt string into a garbled form
{
$key = $this->key_key;
$this->errors = array();

// convert $key into a sequence of numbers
$fudgefactor = $this->_convertKey($key);
if ($this->errors) return;

if (empty($source)) {
$this->errors[] = 'No value has been supplied for encryption';
return;
} // if

// pad $source with spaces up to $sourcelen
while (strlen($source) < $sourcelen) {
$source .= ' ';
} // while

$target = null;
$factor2 = 0;

for ($i = 0; $i < strlen($source); $i++) {
// extract a character from $source
$char1 = substr($source, $i, 1);

// identify its position in $scramble1
$num1 = strpos($this->scramble1, $char1);
if ($num1 === false) {
$this->errors[] = "Source string contains an invalid character ($char1)";
return;
} // if

// get an adjustment value using $fudgefactor
$adj = $this->_applyFudgeFactor($fudgefactor);

$factor1 = $factor2 + $adj; // accumulate in $factor1
$num2 = round($factor1) + $num1; // generate offset for $scramble2
$num2 = $this->_checkRange($num2); // check range
$factor2 = $factor1 + $num2; // accumulate in $factor2

// extract character from $scramble2
$char2 = substr($this->scramble2, $num2, 1);

// append to $target string
$target .= $char2;

//echo "char1=$char1, num1=$num1, adj= $adj, factor1= $factor1, num2=$num2, char2=$char2, factor2= $factor2<br />\n";

} // for

return $target;

} // encrypt

// ****************************************************************************
function getAdjustment ()
// return the adjustment value
{
return $this->adj;

} // setAdjustment

// ****************************************************************************
function getModulus ()
// return the modulus value
{
return $this->mod;

} // setModulus

// ****************************************************************************
function setAdjustment ($adj)
// set the adjustment value
{
$this->adj = (float)$adj;

} // setAdjustment

// ****************************************************************************
function setModulus ($mod)
// set the modulus value
{
$this->mod = (int)abs($mod); // must be a positive whole number

} // setModulus

// ****************************************************************************
// private methods
// ****************************************************************************
function _applyFudgeFactor (&$fudgefactor)
// return an adjustment value based on the contents of $fudgefactor
// NOTE: $fudgefactor is passed by reference so that it can be modified
{
$fudge = array_shift($fudgefactor); // extract 1st number from array
$fudge = $fudge + $this->adj; // add in adjustment value
$fudgefactor[] = $fudge; // put it back at end of array

if (!empty($this->mod)) { // if modifier has been supplied
if ($fudge % $this->mod == 0) { // if it is divisible by modifier
$fudge = $fudge * -1; // make it negative
} // if
} // if

return $fudge;

} // _applyFudgeFactor

// ****************************************************************************
function _checkRange ($num)
// check that $num points to an entry in $this->scramble1
{
$num = round($num); // round up to nearest whole number

$limit = strlen($this->scramble1);

while ($num >= $limit) {
$num = $num - $limit; // value too high, so reduce it
} // while
while ($num < 0) {
$num = $num + $limit; // value too low, so increase it
} // while

return $num;

} // _checkRange

// ****************************************************************************
function _convertKey ($key)
// convert $key into an array of numbers
{
if (empty($key)) {
$this->errors[] = 'No value has been supplied for the encryption key';
return;
} // if

$array[] = strlen($key); // first entry in array is length of $key

$tot = 0;
for ($i = 0; $i < strlen($key); $i++) {
// extract a character from $key
$char = substr($key, $i, 1);

// identify its position in $scramble1
$num = strpos($this->scramble1, $char);
if ($num === false) {
$this->errors[] = "Key contains an invalid character ($char)";
return;
} // if

$array[] = $num; // store in output array
$tot = $tot + $num; // accumulate total for later
} // for

$array[] = $tot; // insert total as last entry in array

return $array;

} // _convertKey

// ****************************************************************************
} // end encryption_class
// ****************************************************************************

?>