Micah LeeSignal is testing out a new feature that encrypts message metadata. Once it's widely deployed, their server will facilitate delivering messages but without having access to who is sending them
Technology preview: Sealed sender for Signal
In addition to the end-to-end encryption that protects every Signal message, the Signal service is designed to minimize the data that is retained about Signal users. By design, it does not store a record of your contacts, social graph, conversation list, location, user avatar, user profile name, ...
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