What Is Full Disk Encryption?

THERE’S BEEN A lot of talk in recent years about encryption and what the FBI terms its “Going Dark” problem—its inability to read the communications of surveillance targets because more and more data is being encrypted. And while the end-to-end messaging encryption that protects data in transit in apps like WhatsApp get a lot of press, it’s a problem that applies equally a data at rest. The kind that full-disk encryption is designed to protect.

Full disk encryption, also known as whole disk encryption, protects data that’s at rest on a computer or phone, as opposed to email and instant messaging data that’s in transit across a network. When done effectively, it prevents any unauthorized person, including phone and computer makers themselves, from accessing data stored on a disk. This means that if you leave your laptop or phone behind in that Uber driver’s car, or some shifty government agent tries to access your computer at an airport or other border crossing, they won’t be able to get at your data without your help—even if they remove the hard drive and place it in another machine.