Decoding the WindowsXP product key / serial number from the digital product id with PHP

decode_win_xp_product_key.php

<?php
/**
 * decodes the product key and returns it as "-"-seperated string
 * @param array of bytes
 * @return string
 */
function decodeProductKey($aHexSrc)
{
    // base24-encoded
    $arrDigits = array('B', 'C', 'D', 'F', 'G', 'H', 'J', 'K', 'M', 'P', 'Q', 'R', 'T', 'V', 'W', 'X', 'Y', '2', '3', '4', '6', '7', '8', '9');

    // get ANSI-code
    for ($i = 0, $m = sizeof($arrDigits); $i < $m; $i++)
    {
        $arrDigits[$i] = ord($arrDigits[$i]);
    }

    $arrHexDigitalPID = $aHexSrc;

    $rCdKey = "";

    for ($i = 24, $m = 0; $i >= 0; $i--)
    {
        $iCurrent = 0;

        for ($j = 14, $n = 0; $j >= 0; $j--)
        {
            $iCurrent =  ($iCurrent << 8) + $arrHexDigitalPID[$j];
            $arrHexDigitalPID[$j] = ($iCurrent / 24);
            $iCurrent = $iCurrent % 24;
        }

        $rCdKey = chr($arrDigits[$iCurrent]) . $rCdKey;

        if ($i%5 == 0 && $i != 0)
        {
            $rCdKey = "-" . $rCdKey;
        }
    }

    return $rCdKey;
}

/**
 * retrieves the encoded product key from whereever
 * @return string
 */
function loadEncodedProductKey()
{
    $rData = extractEncodedProductKey("YOUR DIGITAL PRODUCTID");
    return $rData;
}

/**
 * extract the encoded product key from the digital product id
 * @param binary string of digital product ID
 * @return array
 */
function extractEncodedProductKey($aDigitalProductId)
{
    $startOffset = 52;
    $sLen = 15;

    $data = toArray($aDigitalProductId);
    $rData = array_slice($data, $startOffset, $sLen);

  return $rData;
}

/**
 * converts a space-seperated string to an array
 * @param string
 * @return array
 */
function toArray($aBinaryData)
{
    $arr = explode(" ", $aBinaryData);
    $rT = array();

    for ($i = 0, $m = sizeof($arr); $i < $m; $i++)
    {
        array_push($rT, hexdec($arr[$i]));
    }

    return $rT;
}
?>