protected function createPool()
	{
		$pool	= "";
		$sets	= array(
			"useDigits"	=> "digits",
			"useSmalls"	=> "smalls",
			"useLarges"	=> "larges",
			"useSigns"	=> "signs",
			);

		foreach( $sets as $key => $value )
			if( $this->$key )
				$pool	.= $this->$value;
		return $pool;
	}