If a single party in a chat has their keys reset that's not a MITM attack because a MITM would need to rekey to both parties. If the two clients communicate vi

If a single party in a chat has their keys reset that's not a MITM attack because a MITM would need to rekey to both parties. If the two clients communicate via at least one uncompromised service to communicate that their counterparty's keys have been reset, they might be able to detect a MITM Keybase's example Cozy Street is not a MITM attack (i.e. an attacker has inserted themselves between two parties and can get the plaintext), it's just impersonation. If it was a real MITM attack both Alice and Bob would get rekey notifications, unless they both confirm whenever they get a rekey notification a MITM attack is possible. I also think that crypto is stuck in the early 90s by thinking real world meetups are the only way to authenticate keys. If you know what your chat friend sounds and looks like, willing to submit a video, and don't think your adversary can fake such a proof, a simple video of you reading your pubkey/safety number is sufficient. Is that scalably practical? no but it is possible. That said: keybase is doing cool novel work, I commend them for advancing the state of the art.