public function authenticate()
    {

        $signer = new RequestSigner();
        $signer->setProvider('USF');
        $authenticator = new RequestAuthenticator($signer, $this->_timeout);

        $key = $authenticator->authenticate($this->_requestWrapper, $this->_keyLoader);

        if ($key) {
            $this->principal = "[HMAC]".$key->getId();
            $this->attributes = [];
            return true;
        }

        return false;

    }