PasswordHash::crypt_private

	function crypt_private($password, $setting)
	{
		$output = '*0';
		if (substr($setting, 0, 2) == $output)
			$output = '*1';

		$id = substr($setting, 0, 3);
		# We use "$P$", phpBB3 uses "$H$" for the same thing
		if ($id != '$P$' && $id != '$H$')
			return $output;

		$count_log2 = strpos($this->itoa64, $setting[3]);
		if ($count_log2 < 7 || $count_log2 > 30)
			return $output;

		$count = 1 << $count_log2;

		$salt = substr($setting, 4, 8);
		if (strlen($salt) != 8)
			return $output;

		# We're kind of forced to use MD5 here since it's the only
		# cryptographic primitive available in all versions of PHP
		# currently in use.  To implement our own low-level crypto
		# in PHP would result in much worse performance and
		# consequently in lower iteration counts and hashes that are
		# quicker to crack (by non-PHP code).
		if (PHP_VERSION >= '5') {
			$hash = md5($salt . $password, TRUE);
			do {
				$hash = md5($hash . $password, TRUE);
			} while (--$count);
		} else {
			$hash = pack('H*', md5($salt . $password));
			do {
				$hash = pack('H*', md5($hash . $password));
			} while (--$count);
		}

		$output = substr($setting, 0, 12);
		$output .= $this->encode64($hash, 16);

		return $output;
	}