/**
  * Create signature
  *
  * @param  Request  $request
  * @param  Consumer $consumer
  * @return string
  * @throws SurvariumException
  */
 public function buildSignature(Request $request, Consumer $consumer)
 {
     $algorithm = $this->getAcceptedAlgorithm();
     return base64_encode(hash_hmac($algorithm, $request->getSignatureString(), $consumer->getPrivateKey(), true));
 }