/**
* Generate the new key
*
* @param string $hash The hash algorithm to be used by HMAC
* @param string $password The source password/key
* @param string $salt
* @param integer $iterations The number of iterations
* @param integer $length The output size
* @throws Exception\InvalidArgumentException
* @return string
*/
public static function calc($hash, $password, $salt, $iterations, $length)
{
if (!Hmac::isSupported($hash)) {
throw new Exception\InvalidArgumentException("The hash algorithm {$hash} is not supported by " . __CLASS__);
}
$num = ceil($length / Hmac::getOutputSize($hash, Hmac::OUTPUT_BINARY));
$result = '';
for ($block = 1; $block <= $num; $block++) {
$hmac = hash_hmac($hash, $salt . pack('N', $block), $password, Hmac::OUTPUT_BINARY);
$mix = $hmac;
for ($i = 1; $i < $iterations; $i++) {
$hmac = hash_hmac($hash, $hmac, $password, Hmac::OUTPUT_BINARY);
$mix ^= $hmac;
}
$result .= $mix;
}
return substr($result, 0, $length);
}
