How Signal Instant Messaging Protocol Works (& WhatsApp etc) - Computerphile

How do instant message apps do end to end encryption when one phone may not even be switched on yet? Dr Mike Pound on the Signal protocol at the core of most messaging apps. Double Ratchet: COMING SOON! https://www.facebook.com/computerphile https://twitter.com/computer_phile This video was filmed and edited by Sean Riley. Computer Science at the University of Nottingham: https://bit.ly/nottscomputer Computerphile is a sister project to Brady Haran's Numberphile. More at http://www.bradyharan.com