End-to-end encryption vexing to some officials . Facebook says it has begun to offer users the option of securing their messages with end-to-end encryption, a service that soon may allow more than a billion account holders — potentially including jihad and other terror groups — to message one another below the radar of law enforcement surveillance. ... By implementing end-to-end encryption, Facebook aims to give its users a way of communicating over the network’s proprietary Messenger application in a manner intended to make correspondence undecipherable to anyone other than the sender and recipient, a possibility that alarms law enforcement officials....