code: private String getAuthMessage() {
          if (clientFirstMessageBare == null) {
              throw new RuntimeException("can't call getAuthMessage without clientFirstMessageBare is set");
          }
          if (serverFirstMessage == null) {
              throw new RuntimeException("can't call getAuthMessage without serverFirstMessage is set");
          }
          if (clientFinalMessageNoProof == null) {
              throw new RuntimeException("can't call getAuthMessage without clientFinalMessageNoProof is set");
          }
          return clientFirstMessageBare + "," + serverFirstMessage + "," + clientFinalMessageNoProof;
      }
docs: Get the AUTH message (as specified in the RFC)