" The best means we have for keeping our keys safe is called “zero knowledge,” a method that ensures that any data you try to store externally—say, for instance, on a company’s cloud platform—is encrypted by an algorithm running on your device before it is uploaded, and the key is never shared. In the zero knowledge scheme, the keys are in the users’ hands—and only in the users’ hands. No company, no agency, no enemy can touch them. "

― Edward Snowden , Permanent Record