Facebook Messenger has become the latest social media app to roll out encryption as a feature, making certain conversations completely private.The new feature will be called "Secret Conversations" and will exist within the regular app - similar to an incognito tab in your web browser.The app, currently used by more than 900million people globally, takes its lead from sister-app WhatsApp, which rolled out end-to-end encryption for its 1billion users across all devices in April.You can start a secret chat with any Facebook friend and the thread will be "end-to-end" encrypted. Only the people communicating can access messages sent. Eavesdroppers such as cyber-criminals, telecoms, governments - and even Facebook itself - cannot read the conversations.There will also be a new "timer" option for every message within the thread, which causes the message to self-destruct after the set time, similar to popular app Snapchat."My teenage daughter just started her first internship and needed her social security number, which is secure but I didn't know how to send it to her with total peace of mind," said David Marcus, who heads the Facebook Messenger unit."We have so many identity theft issues [in the US], that I wouldn't send it by e-mail or want it to stay in a thread."The secret conversation threads will be available on only one device for added security, and will not be accessible through the cloud. ..