Sorry, but his is a major security flaw. WhatApp, their mothership Facebook, or any party who can coerce them into doing so (e.g. the US government), can use th

Sorry, but his is a major security flaw. WhatApp, their mothership Facebook, or any party who can coerce them into doing so (e.g. the US government), can use this to rekey targets with their own keys, virtually undetectable by most regular users, thereby completely MITMing the message exchanges. Even moxie, who created this stuff, more or less admitted this[0], by saying the rekeying notification is the only defense, but that one is off by default in whatapp last I checked (which moxie confirmed[1]), which makes whatapp insecure by default at the very least. I wouldn't be surprised if WhatApp servers know if this notification setting is on or off, which would enable them to e.g. target people with insecure default settings only to avoid detection. I already said this in [0], but let's repeat it: This is essentially the same as if a webbrowser would just accept any TLS certificate without showing a warning no matter if valid or the issuer trust. Sure, this is hard problem to solve UX-wise and user-education-wise, but that doesn't excuse that you advertise your known-and-deliberately-insecure-by-default default-MITMable product as "secure communication using end-to-end encryption". [0] https://news.ycombinator.com/item?id=13395869 https://news.ycombinator.com/item?id=13395869 [1] https://news.ycombinator.com/item?id=13396393 https://news.ycombinator.com/item?id=13396393