> if you have 10k followers you’re proposing to encrypt every post 10k times?

I mean, yes. Why you’re sending a “private” post to ten thousand people is another question.

that sounds like a UX nightmare, what happens when you approve a new follower? do you encrypt your entire post history for them? how long would that take ?

> do you encrypt your entire post history for them?

Sure.

> how long would that take ?

Shouldn’t take THAT long. This is the cost of privacy.

Imo society is wasting compute on less interesting problems than this one

Oh! This is about posts! Sure, otherwise it's not private really.

in my opinion the actual solution is mastodon should stop pretending that private accounts are a thing when it is just UI fairy dust

That's not how it should work though. The post should get encrypted only once with a symmetric key i.e. AES, and then this gets encrypted with each of the followers' public keys. So it's not the post itself but the encryption key that must be scaled. This is how PGP-encrypted E-mail works.

you’re still encrypting n-times, the post needs to be stored n-times and that’s even before thinking about key rotation and server portability

this is not practical