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Matrix Metadata Problem: the server sees everything except your messages (dfrws.org)
submitted 1 month ago by to c/matrix@programming.dev
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Matrix Metadata Problem: the server sees everything except your messages

People pick Matrix because of end-to-end encryption. But E2EE only protects message content — everything around it is plaintext.

The server sees:

  • Your ID, IP, client type and version, device you use
  • Your presence, typing status, read receipts
  • Which rooms you join and when you join/leave
  • Who else is in those rooms → your entire social graph
  • Room names, topics, avatars (all plaintext state)
  • For every message: who sent it, which room, a millisecond timestamp, type, size

And federation copies all of that to every other server whose users are in the room. Your "social footprint" isn't one copy — it's as many as there are servers.

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[–] 2 points 1 month ago (1 child)

Things that are good to understand, but also conclusions you can come to by just thinking a bit about how it would have to work. Some of it is less obvius, like session details. I actually don't know, does session info federate? Can't see why it would need to.

A sealed envelope still has to have recepient info, and while it would be possible to have the server forget a lot of info after delivery, you can't enforce that.

One of these is also an exaggeration, federation doesn't copy everything to every other server, only the parts of your activity to servers that participate in that particular activity.

If you chat on your matrix instance with another user on your instance, only your instance records the event.

If you DM someone on another instance, only your and their server have a record of that. Not every matrix server on the network, that'd be absurd.

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