The fingerprint sensor on your phone is the key to revealing all the private information stored on the device, and it does a good job of keeping it secure. However, if a thief were to get hold of your fingerprint and your phone, it wouldn’t provide much protection anymore. Think that’s unlikely? The National Institute of Informatics in Japan has warned that photos posted online in which the “peace sign” is flashed, may be all that’s need to hack the system.

Professor Isao Echizen says smartphone camera technology is now so great, and the images taken so full of detail, fingerprints can be copied simply by showing your fingertips to the camera. It’s not just super close-ups that are the problem, as his experiments showed data could be grabbed from photos taken up to three meters away. Unless you’re very bizarrely shaped, or have a particularly long selfie stick, that covers pretty much every selfie you’re likely to take.

Flashing the peace sign in a selfie is popular all over the world, but particularly in Asia, where it’s common for everyone from school children to celebrities to stick two fingers up at the camera. The problem is compounded by photos being shared and stored online, creating a gallery of fingerprints for thieves to exploit. The professor points out that unlike a stolen password, which can be quickly changed, your fingerprints are with you forever.

It’s not the first time we’ve been warned against photographing our fingers. In 2014, a hacker demonstrated almost exactly the technique described above, where a German politician’s fingerprints were replicated from photos taken in public, from a distance of around three meters. A 3D mold of the fingerprint was created from the images, which could be used to unlock a secured phone.

What’s the solution here, assuming you don’t want to give up the ever-popular peace sign pose? At the National Institute of Informatics, a special transparent film is being developed that will stick to your fingers and mask the print itself. Unfortunately, it’s not expected to be ready for another two years, but when it does arrive it won’t affect how you unlock your phone. In the meantime, keep your fingertips out of the frame if you’re worried, or wear gloves if you’re really paranoid.

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