Since adding the feature in April, 2016, the Whatsapp app (or really its parent, Facebook) has paraded its "end to end encryption" as the reason to use it above all other smartphone message applications. It can handle calls, messages, video, files and just about everything any computer can and, because it's encrypted end to end, nobody can read, see or hear any of it unless you want them to. 

The pitch has worked; over a billion people now use the app and it is particularly prominent among people who need encryption -- the computer protocol that makes reading your message impossible for anyone but the person you're sending it to.

Activists, particularly, use Whatsapp to communicate everything from places for emergency demonstrations to important announcements to the latest information about their personal lives. Whatsapp is, in effect, a universe of communications for a billion people. It does everything and everything it does is encrypted. With Whatsapp, they've been saying, you are safe from intrusion and spying.