A reminder that your phone number is metadata. And people who think metadata is "just" data or that cross-referencing is some kind of sci-fi nonsense, are fundamentally misunderstanding how modern surveillance works.

By requiring phone numbers, Signal, despite its good encryption, inherently builds a social graph. The server operators, or anyone who gets that data, can see a map of who is talking to whom. The content is secure, but the connections are not.

Being able to map out who talks to whom is incredibly valuable. A three-letter agency can take the map of connections and overlay it with all the other data they vacuum up from other sources, such as location data, purchase histories, social media activity. If you become a "person of interest" for any reason, they instantly have your entire social circle mapped out.

Worse, the act of seeking out encrypted communication is itself a red flag. It's a perfect filter: "Show me everyone paranoid enough to use crypto." You're basically raising your hand.

So, in a twisted way, Signal being a tool for private conversations, makes it a perfect machine for mapping associations and identifying targets. The fact that it operates using a centralized server located in the US should worry people far more than it seems to.

The kicker is that thanks to gag orders, companies are legally forbidden from telling you if the feds come knocking for this data. So even if Signal's intentions are pure, we'd never know how the data it collects is being used. The potential for abuse is baked right into the phone-number requirement.