Pulling faces could become the next type of password used to unlock Android phones and tablets.
Google filed a patent for the technology last year, but it has only just been published. The document suggests that the software could use a "facial landmark" in order to confirm that a user looks like the device's holder and also carries out the correct action (such as frowning, smiling or sticking their tongue out).
This system is said to work by comparing two images taken from a video of the device user's face, to determine if the changes between them show that the correct gesture has been made. In order to check the accuracy of the process, the device will study other frames to see that the person had made the correct movements in sequence to achieve the gesture and to also ensure that the person was visible in all frames.
As well as this, the software could look at the change in angle of the user's face to eliminate the risk that fake gestures are animated on top of a still image. These security advances are said to tackle criticisms of current face detection software.
Alan Woodward, chief technology officer at the consultancy Charteris said, "I would expect people will still use traditional passwords for some time to come."
Google has previously suggested that specific facial expressions could prevent their existing Face Unlock system being hoodwinked by photos. This is following last year's introduction of a "liveness check" that required users to blink at their device to prevent the program from being fooled by a photograph. However, this security measure was undermined by the work of security researchers from the University of British Columbia.