Briar is a messaging app designed for activists, journalists, and anyone else who needs a safe, easy and robust way to communicate. Unlike traditional messaging tools such as email, Twitter or Telegram, Briar doesn't rely on a central server - messages are synchronized directly between the users' devices. If the Internet's down, Briar can sync via Bluetooth or Wi-Fi, keeping the information flowing in a crisis. If the Internet's up, Briar can sync via the Tor network, protecting users and their relationships from surveillance.
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briar / briar
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Torsten Grote
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Before the introducee sends her ACK, she derives a master key from the ephemeral shared secret as before. Two nonces and a MAC key are then derived from the master key. The local introducee signs one of the nonces and calculates a MAC over her own identity public key, ephemeral public key, transport properties and timestamp. The local introducee includes the signature and MAC in her ACK. On receiving the remote introducee's ACK, the local introducee verifies the signature and MAC. Should the verification fail, an ABORT is sent to the introducer and the remote introducee that was added as inactive is deleted again.