Implementation of the PBKDF2 key derivation function as described in RFC 2898.

gistfile1.aw

<?php
/**
 * Implementation of the PBKDF2 key derivation function as described in
 * RFC 2898.
 *
 * @param string $PRF Hash algorithm.
 * @param string $P Password.
 * @param string $S Salt.
 * @param int $c Iteration count.
 * @param mixed $dkLen Derived key length (in octets). If $dkLen is FALSE
 *                     then length will be set to $PRF output length (in
 *                     octets).
 * @param bool $raw_output When set to TRUE, outputs raw binary data. FALSE
 *                         outputs lowercase hexits.
 * @return mixed Derived key or FALSE if $dkLen > (2^32 - 1) * hLen (hLen
 *               denotes the length in octets of $PRF output).
 */
function pbkdf2($PRF, $P, $S, $c, $dkLen = false, $raw_output = false) {
    //default $hLen is $PRF output length
    $hLen = strlen(hash($PRF, '', true));
    if ($dkLen === false) $dkLen = $hLen;

    if ($dkLen <= (pow(2, 32) - 1) * $hLen) {
        $DK = '';

        //create key
        for ($block = 1; $block <= $dkLen; $block++) {
            //initial hash for this block
            $ib = $h = hash_hmac($PRF, $S.pack('N', $block), $P, true);

            //perform block iterations
            for ($i = 1; $i < $c; $i++) {
                $ib ^= ($h = hash_hmac($PRF, $h, $P, true));
            }

            //append iterated block
            $DK .= $ib;
        }

        $DK = substr($DK, 0, $dkLen);
        if (!$raw_output) $DK = bin2hex($DK);

        return $DK;

    //derived key too long
    } else {
        return false;
    }
}