Efficient way to confirm identity I am working on a multiplayer game.

I have a central server which handles all data transmission and coordinates all games. Clients which involved in a single session send requests to do actions to the server, those actions are checked and the consequences are pushed to all clients.

I am looking for a way for the server to confirm whether the request came from authorised client (a specific player).

I originally planned to use RSA, but it's too computationally expensive, and is an overkill since I don't need really need request data encrypted.

What should I do/use for this purpose?
Traditionally, one would just use an implementation of DTLS and some form of challenge-response player authentication.