public function addHash($options)
    {
        if (is_string($options)) {
            $options = array($options);
        } else if (!is_array($options)) {

            throw new Zend_Validate_Exception("False parameter given");
        }

        $known = hash_algos();
        if (!isset($options['algorithm'])) {
            $algorithm = 'crc32';
        } else {
            $algorithm = $options['algorithm'];
            unset($options['algorithm']);
        }

        if (!in_array($algorithm, $known)) {

            throw new Zend_Validate_Exception("Unknown algorithm '{$algorithm}'");
        }

        foreach ($options as $value) {
            $this->_hash[$value] = $algorithm;
        }

        return $this;
    }