And it's an excellent policy. Cook said if you create a back door, then anyone can creep in and access all your private stuff. Too much private stuff in a personal device; you don't want back doors. Back in the day when I did machine programming on IBM mainframes, I created back doors for myself. It's just something software engineers did, and hoped no one else would expose it. I could give highest priority to my stuff, and completely take over the mainframe. Years later I noticed no one discovered them and they were still in there. I'm sure Apple goes over every line of code carefully to make sure their OS is secure and free of back doors.