Making your phone screen blurry could stop people snooping on you

Thanks to the way human eyes work, a system that makes your phone screen blurry can prevent people reading it from a distance while still remaining legible up close.

Worried about people taking a peek at your phone screen? Now there’s a simple solution – make the screen so blurry that it can’t be snooped on.

Privacy, if you don’t mind squinting

Brian Tang, Kang G. Shin

Brian Jay Tang and Kang Shin at the University of Michigan say their system keeps your information private by blurring the screen in such a way that it is readable up close but indecipherable at a distance. And unlike physical privacy films that are stuck to the screen, their system can be turned on and off at will.

Tang says that the “Eye-Shield” system can be added to existing phones with a software update and requires no new hardware. The system works because our eyes can only distinguish two nearby sources of light – in this case pixels – as separate when we are close enough to them. The software takes advantage of this and changes what is shown on the screen by creating chequered grids of pixels that can be recognised as characters or shapes when up close, but blur into a single incoherent blob at a further distance.

There is a trade-off in readability for the person actually holding the phone, but tweaking the amount of blur introduced can make it legible while also secure, says Tang.

“The idea I have for deployment is you’re in a public setting and you need to access your banking details, or maybe enter in a passcode – so you just quickly turn this on from the menu and then enter whatever details you need to, look at whatever you need to do. And then, once you’re done with the sensitive stuff, you can just turn it right back off,” he says.

In tests, Eye-Shield reduced the ability of those looking over the user’s shoulder to recognise text and images by roughly 60 per cent. The researchers are currently in talks with a smartphone manufacturer about adding the technology to commercial devices.

One downside to Eye-Shield is that it requires some processor power to calculate how to effectively blur the screen. In tests, this never used more than 10 per cent of the processor’s power, and the researchers say it should have little effect on battery life, but Tang says that reducing the resolution when privacy mode is engaged could reduce battery drain even further.

Reference:

arXivDOI: 10.48550/arXiv.2308.03868