function setPublicKey($key = false, $type = false)
    {
        // if a public key has already been loaded return false
        if (!empty($this->publicExponent)) {
            return false;
        }

        if ($key === false && !empty($this->modulus)) {
            $this->publicExponent = $this->exponent;
            return true;
        }

        if ($type === false) {
            $types = array(
                self::PUBLIC_FORMAT_RAW,
                self::PUBLIC_FORMAT_PKCS1,
                self::PUBLIC_FORMAT_XML,
                self::PUBLIC_FORMAT_OPENSSH
            );
            foreach ($types as $type) {
                $components = $this->_parseKey($key, $type);
                if ($components !== false) {
                    break;
                }
            }
        } else {
            $components = $this->_parseKey($key, $type);
        }

        if ($components === false) {
            return false;
        }

        if (empty($this->modulus) || !$this->modulus->equals($components['modulus'])) {
            $this->modulus = $components['modulus'];
            $this->exponent = $this->publicExponent = $components['publicExponent'];
            return true;
        }

        $this->publicExponent = $components['publicExponent'];

        return true;
    }