Ask HN: Is there a decentralized protocol that is private by default?

Hi, I am curious if there is a decentralized protocol that only allows ppl you approve to see what you posted online. It is a followup for this: https://news.ycombinator.com/item?id=41267877 And related to this comment: https://news.ycombinator.com/item?id=41264716#41268473