Numbers in my eyes, patterns in other people's eyes... Development of foldable phone peeping prevention technology

A domestic research team has devised a way to protect personal information by using the screen reflection of mobile phones.

POSTECH announced on the 10th that Professor In-seok Hwang of the Department of Computer Engineering and Gyu-sik Lee's master's research team, together with Professor Jun Han of the Department of Computer Science at the Korea Advanced Institute of Science and Technology (KAIST), have developed a technology that uses the reflection that occurs between the two screens of a foldable phone to prevent people nearby from peeping.

In places where many people ride, such as buses, there are cases of people peeking at other people's cell phone screens or even stealing personal information.

Accordingly, the research team paid attention to the fact that when a foldable phone is folded halfway like a laptop, the light from one screen is reflected like a mirror on the opposite screen.

The research team applied this point and introduced a method of dividing the numbers to be displayed on the screen into two images whose contents cannot be seen by looking at them separately and displaying them on both screens.

This technology shows the original numbers by overlapping the directly visible image and the reflected image to the user's eyes, but to someone looking at it from a different angle, the two pieces are misaligned and only appear as a jumbled pattern.

Even if the user moves his head slightly, the front camera of the smartphone follows the position of the user's eyes in real time, calculates the angle at which the phone is folded, and changes the positions and shapes of the two images at that time.

This technology can be implemented by introducing software into foldable phones currently sold without special films or additional devices.

As a result of the experiment, existing protective films were able to read most numbers even at 30 degrees left and right, but the research team's technology was unable to read numbers even if they were 7.5 degrees out of the user's line of sight.

Even in an experiment that recreated a password input situation, peripheral observers recognized only 0.65 of the 10 keypad numbers on average.

This research was presented at 'ACM UIST 2026', the most prestigious international academic conference in the field of user interfaces, held in Detroit, USA from the 2nd to the 5th, and was selected for the excellence award in the demo category.

Professor Hwang In-seok said, “It is meaningful that screen reflection, which was considered annoying, has been changed into a means of protecting user information.”