this post was submitted on 06 Mar 2024
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It would be big news if Signal failed to disclose a little-known caveat, let alone directly lie.
The functionality has been tested for at least a year, right? And the client side code is open source. They aren't hiding anything. The Molly fork has already implemented the same functionality.
Don't get me wrong. I like the signal foundation. They do great work. I'm just hesitant to claim that usernames are in anonymous way to talk to people on the internet.
If your model of signal is just I can communicate and encrypted with people I already know and who know me. Everything's fine. Nothing about the server compromises that. But when you introduce can I talk people anonymously, the model doesn't support that. Because the server has the capability to deanonymize.
If nothing else, somebody could simply brute force all the phone numbers, until their named contact shows up.
I just did some minor testing, right now, if you have a username that you want to post on the internet, like embarrassing_contact.01, like for political dissidents organizing, alternative lifestyle organization, disclosing sensitive information etc. if you already have the contact on your phone, but you try to send a message to the username. Signal will tell you oh it's the same person you already have this contact. So right there is a proof of concept of deanonymizing people
If that is your threat model you can put your phone number privacy to no one. Then I can't see you use Signal even if I have your contact with your phone number saved and adding you with your username won't show you as my phone contact with the same phone number.
That's good feedback, I wasn't aware it existed. Thank you