On: Delta Chat

[akerl_]

Reading their docs, it seems like this uses Trust-on-first-use key exchange, so if there's an attacker passively observing the network at that point, they can MITM all future communications.

Also, the Autocrypt Level 1 spec, which this seems to implement, appears to be based on PGP, with the following caveat: "Sometimes Autocrypt recommends to send cleartext mail even though encryption appears technically possible."

[titanomachy → akerl_]

I don't think that's how TOFU works. Doesn't attacking it require an active attacker to substitute his own public key at the start?

[e12e → titanomachy]

Yes, if the attacker is strictly passive, tofu with public key should be fine. That the attacker is strictly passive is a pretty strong assumption though!