[psranga]

I take this blog post as confirmation that:

1) ANY one message can be intercepted even if the sender exhibits ideal levels of alertness [Whatsapp server drops message to recipient; sends a rekey request with a fake key; message is intercepted since fake key was generated by server. Sender will see a warning if they turned on that setting (default is to show no warning), but it's too late].

2) Only Whatsapp has this vuln, not Signal app.

3) Depending on sloppiness of sender, more extensive interception is possible. [E.g., server not supplying delivery reports + sender doesn't have warning for key changes + sender sloppy about noticing lack of double check mark => full transcript can be generated]

[dangero]

Best summary I've seen. There are two significant facts here that surprised me: 1. The double checkmark has security implications. How would a typical user know that? 2. Even if you are completely vigilant, follow best practices, etc, Whatsapp messages can be intercepted. They claim this is a "wontfix" UX choice. I'm skeptical why the non-default feature cannot even provide the protection that almost everyone assumed it would.

[Vinnl]

> How would a typical user know that?

I think that's basically the main problem: there is no way to get a typical user to understand security implications of anything without having that user give up before reaching that point...