It's a tricky problem. I could see enterprise solutions for private GPS networks that have signed messages similar to an asymmetric JWT signature. That way the

It's a tricky problem. I could see enterprise solutions for private GPS networks that have signed messages similar to an asymmetric JWT signature. That way the message can be passed around and the client can assert if the message has been tampered with. That approach requires the satellite networks to have knowledge of the key pairs for each client. Not something you'd see the government provide, but a possibility for commercial applications.