Even if an attacker such as the government runs the coordination and relay servers, and the IdP, they will not be able to decrypt any traffic in tailnet.
The secret keys remain on device, and traffic is end to end encrypted. There is no mechanism in
the client agents to send out the secret keys. The coordination server receives the public keys and metadata.
I see I did have a misunderstanding. I believe there is still the meta data angle, but yes, private keys on endpoints would ensure E2EE. I will update my comment.