Face Unlock launched with a bit of controversy and skepticism because it was easy to game the system. A person could hold up a picture of the device owner and unlock the phone because the unlock screen required only that a facial match be detected. In Android 4.1 Jelly Bean, Face Unlock ups the ante with a “Liveness check” feature.
Jelly Bean has an optional security feature that adds an extra layer of security for face unlock. When someone sets the phone to enable “Liveness check,” the phone will only unlock when the front-facing camera detects that someone blinks when prompted. If someone fails to blink fast enough or tries to use a static image, the phone will not unlock unless the correct backup gesture/pin lock is entered.
Requiring blinking makes Face Unlock smarter, but it’s not foolproof. I managed to trick the phone into letting me in by holding up a video of me blinking. However, considering the extreme unlikeliness that someone has video of you blinking enough times and can quickly line up both screens, I seriously doubt that should be too much of a concern.
Like I said when Face Unlock was first available, this is more about novelty than it is security. That’s still the case because a pin or gesture lock will still be more secure than Face Unlock, but an improvement is always welcome. This is great for people who worried about Face Unlock being duped by someone holding up a Facebook photo of the owner, and the facial recognition seems to be much faster than it was on Ice Cream Sandwich.
Jelly Bean owners can enable blink detection by taking the following steps:
Settings > Security
Tap “Screen Lock” and follow steps for Face Unlock
Return to Settings screen and tap “Liveness check”