Those are really big numbers. You're talking like bigger than the number of stars in the universe sized number space for these nsecs. So they're safe from brute forcing. You just have to keep it safe from theft.

Just adversarial thinking I guess. Sooner or later we will probably all have cold storage privkeys.

I would like to test if I have a relay and accept/create posts on behalf of anyone if nostr clients connected to the relay show them.