Comment by tptacek
2 years ago
Records of precisely who you talk to are being kept serverside because of that decision. Maybe that's totally fine for you! Most people have pretty unserious secure messaging threat models (I don't mean that as a value judgement).
The same is likely true of Signal, no? Traffic analysis on AWS' edge would tell you precisely who is talking to who, and user identities are tied to legal identities via phone numbers. Maybe Signal doesn't store this data serverside, but there are entities with both the capability and motivation to obtain it. I bet there are Signal XKEYSCORE selectors.
No, it's not. Traffic analysis is potent, but it is not a literal SQL database of who has talked to who when.
Signal's "sealed sender" feature means it doesn't even know who sent you the message (all they can see is an IP address):
https://signal.org/blog/sealed-sender/
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So the problem is the same: trusting the server. At least small Matrix servers aren't huge targets for attacks, since they don't serve so many users.
Also on Matrix you can run your own server.
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