Specification:
https://github.com/fedi-e2ee/public-key-directory-specificat...I've been working on solving this problem so we can have end-to-end encryption for DMs on ActivityPub (and therefore Mastodon).
I thought I'd share it here in case anyone was interested in this work.
Edit: I see that this is primarily intended for federated social networks, but should be reusable for other uses. However for other e2ee systems (e.g. messaging, filesystems) where hiding your social graph is important, wouldn't a key directory be able to infer (part of) your social graph by recording which lookups you make? What's the best way to mitigate that?