Photon and Playfab - PhotonNetwork.playerName Hacking

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Hey guys,

I'm using the Playfab Authentication to Login with this and send a Token to Photon for a safe Player-Login.

I programmed my whole game already using Photon and everything is working perfect, and I use the Other PlayerNames to make Kills, damage and so on, the mechanics for my game are already done.

Now what I'm thinking of: Is using PhotonNetwork.playerName the right solution? How can I make sure a player who logged in with Playfab will have his DisplayName as PhotonNetwork.playerName and another Player who hacked my unity client is not allowed to use another Player's DisplayName as his PhotonName?

Greetings,
Dario