How can the rpc client send the key to the rpc server on hadoop

[Jone Zhang]

I want to design an authentication mechanism with the following details.
1. Key information is saved in core-site.xml of the HDFS clients.
2. For request, rpc client send the key to rpc server.
3. The namenode verifies the key when receiving it.
My question is, how can the rpc client send the key to the rpc server?

Thanks