How to trust servers in a network where anyone can add its own

Question

I'm building a multiplayer game where anyone can add its own server but there is only one central server that contains the database where player information, like experience and gold, are stored. To authenticate as a game server and thus have authorization to give gold to a player, you join a JWT, issued by me, to your requests. However, whoever owning the server could use this token and boost up his own characters. My problem is how can I trust a game server request? To me, except by obfuscating the communication between a game server and the central one, there is not much to be done. But this problem reminds me of cryptocurrencies, would a blockchain help me here?