Post #4371972
2026-08-04 05:46 UTC
Replies (1)
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@david_chisnall@infosec.exchange 2026-08-04 10:08
@Kukmetz@social.vivaldi.net @voorstad@mastodon.nl Metadata is an overloaded term. In the context of your quotes, it means the connection graph. The key thing is knowing who is talking to whom. Even if the message body is encrypted, knowing when messages are sent, when they are received, and who sends and receives them gives you an enormous amount of information. Simple clustering lets you determine who is in a particular group. Want to know who is in a terrorist cell or thinking of forming a union? Look for the people in a strongly connected graph containing a known terrorist or union organiser. You don't need to see the message body to do any of this. This is why protocols like XMPP are not suitable for modern threat models: they make all of this information visible to server operators and a single malicious server operator can passively extract a lot of this information. The Signal protocol is designed so that most of this is not visible to the server at all. That's why it doesn't matter (except for availability) that they host on Amazon: If you are designing the protocol properly, the server is not trusted for confidentiality or integrity. If the protocol requires you to trust the server for these properties, then it is not designed for security. If the argument for Threema is who hosts their servers, then that tells me that they have not designed their protocol with a threat model that is satisfactory: if they had designed it properly then it wouldn't matter where their servers or who operated them because they wouldn't be able to extract any useful information. And, from what I've seen of Threema's protocol and implementation, I certainly wouldn't trust them.