If you've used Windows 8, or even just seen the ads for it, you'll know it has a feature called Picture Passwords.
You choose a picture, any picture, and then "annotate" it with three finger movements: you can tap a point, draw a stroke, or sweep a circle.
The picture helps you to remember where you made the gestures, so you can repeat them reliably enough to pass the test and unlock your device.
If you have a touch screen tablet, Picture Passwords are surprisingly handy. (Pun intended.)
But how safe are they?