Block their domain and call it a day. The only thing that comes out of there is relayed spam.
How about this..
- User creates a group chat
- The client creates a private/public keypair for the group
- User invites others to join, which sends them the keypair
- When a user posts to the group chat, their inner message is signed by their private key. That signed message is wrapped in an outer message signed by and encrypted with the group chat private key
- Timestamps are used to properly order messages in the group chat
That would keep the group chat membership private. Subscribed clients watch for new messages sent to the group's npub.
Similar to disk enceyption? Encrypt the message text with a master key, encrypt the master key with each user key, and include the ID:encKey pairs in the event.
The big downside is an interested party could track which user IDs were participating in the group chat. Probably better to start fresh with a new NIP type.
When this passes for entertainment, and the vast majority of normies don't see a problem with it, you have to wonder whether our nation deserves what's coming..
Testing NiP-13 proof of work..