Greetings!
A friend of mine wants to be more secure and private in light of recent events in the USA.
They originally told me they were going to use telegram, in which I explained how Telegram is considered compromised, and Signal is far more secure to use.
But they want more detailed explanations then what I provided verbally. Please help me explain things better to them! ✨
I am going to forward this thread to them, so they can see all your responses! And if you can, please cite!
Thank you! ✨
They have to know who the message needs to go to, granted. But they don’t have to know who the message comes from, hence why the sealed sender technique works. The recipient verifies the message via the keys that are exchanged if they have been communicating with that correspondent before or else it is a new message request.
So I don’t see how they can build social graphs if they don’t know who the sender if all messages are, they can only plot recipients which is not enough.
Anyone who’s worked with centralized databases can tell you that even if they did add something like that, with message timestamps, it’d be trivial to find the real sender of a message. You have no proof that they even use that, because the server is centralized, and closed source. Again, if their response is “just trust us”, then its not secure.
From what I understand, sealed sender is implemented on the client side. And that’s what’s in the github repo.
How does that work? I wasn’t able to find this. Can you find documentation or code that explains how the client can obscure where it came from?
https://signal.org/blog/sealed-sender/ explains the feature.
https://github.com/signalapp/Signal-Android/issues/13842 has some links into the code base showing where sealed sender is implemented.
Okay. But this method doesn’t address that the service doesn’t need the message to include the sender to know who the sender is. The sender ('s unique device) can with 100% accuracy be appended to the message by the server after it’s received. Even if we trust them on the parts that require trust, the setup as described by the blog doesn’t do anything to prevent social graphs from being derived, since the sender is identified at the start of every conversation.
If we trust them not to store any logs (unverifiable), then this method means they can’t precisely know how long a conversation was or how many messages were exchanged. But you can still know precisely when and how many messages both participants received, there’s just a chance that they’re talking to multiple people. Though if we’re trusting them not to store logs (unverifiable), then there shouldn’t be any data to cross reference to begin with. So if we can’t trust them, then why are we trusting them not to take note of the sender?
The upside is that if the message is leaked to a third-party, there’s less info in it now. I’m ignoring the Github link, not because I don’t appreciate you finding it, but because I take the blog-post to be the mission statement for the code, and the blog doesn’t promise a system that comprehensively hides the sender’s identity. I trust their code to do what is described.