The extra opt-in security feature has successfully passed trials and is now live for all 1 billion users of the service. A few months ago Facebook started testing its very own end-to-end encryption in Messenger and starting today the feature is available to all users. Just like WhatsApp, another IM company that already offers the feature, Messenger uses the Signal Protocol developed by Open Whisper Systems. To get an end-to-end encrypted chat with someone, you'll need to start what is called a Secret Conversation with that person. The option can be accessed by pressing the person's name...
Source: http://www.gsmarena.com/facebook_messengers_endtoend_encryption_is_now_live_for_all_users-news-20893.php
