Edward Snowden’s messenger app of choice has just made itself even more secure from prying eyes. While Signal already sends end-to-end encrypted messages, the company has made those messages even more secure. As Signal explains in a blog post, it has created a way for the sender of a message to be completely anonymous in the message’s metadata, so not only could an outside party not read the content of a message if it is intercepted in transit, but they now cannot even see who is sending the message. The feature is dubbed “sealed sender.” As Signal explains:
When you send a traditional piece of physical mail, the outside of the package typically includes the address of both the sender and the recipient. The same basic components are present in a Signal message. The service can’t “see into” the encrypted package contents, but it uses the information written on the outside of the package to facilitate asynchronous message delivery between users.
While the service always needs to know where a message should be delivered, ideally it shouldn’t need to know who the sender is. It would be better if the service could handle packages where only the destination is written on the outside, with a blank space where the “from” address used to be.
Right now, the feature is available in beta builds of the Signal app, but will be coming to all users in the future, and when it does, it will be turned on by default.
— Signal (@signalapp) October 29, 2018