End-to-end encryption: device verification (for device being verified)

[bradlegge]

"Displays a passphrase (e.g. ""horse staple pink wallet mouse"") that can be sent 'out of band' to the verifier. The passphrase is specific to the verifier. This can be triggered by:

• Hitting the 'Verify yourself with this user' button on their Member Info panel

We could also trigger this from User Settings somewhere, but if we're making it per-verifier i'm not sure this buys much more than additional complexity."