The use of PIN codes or the use of a schema, these are the current methods offered by most smartphone manufacturers to their customers. A computer science research team at the University of Stuttgart reveals that, whenever one of these operations is carried out, a trace of heat remains on the screen.
The team explains how the use of a thermal camera can make it possible to blow the lock, giving a third party access to the privacy of the owner of the device. Finally, it proposes solutions to what it has called “thermal attack.”
First – A few figures
The team of researchers reveals that a third party with the developed thermal attack process could reveal it successfully in 72 to 100% of the cases within 30 seconds of the user introducing the lock.
Overview of the process
To achieve this, the hacker should have a thermal camera. Its use would then allow it to collect the traces of heat on the display and make a thermal image, which would then be passed to a software thermal analyzer to convert the data to grayscale with noise reduction (see below picture below).
The isolation of the hot spots in the image would then reveal the lock, whether it be a PIN code or a diagram would then be passed to a software thermal analyzer to convert the data into grayscale with noise reduction.
The researchers say that the results obtained depend very much on the sensitivity of the thermal camera. A thermal camera of better sensitivity than that used in the experiment would allow the time interval in which it will still be possible to reveal the code at 60 seconds. They also foresee the generalization of this concept to all devices equipped with touch screens with additionally the software implementation of neural networks to boost the thermal analyzer in robustness.
Recommendations of the research team
- Using longer PIN codes has the effect of significantly reducing the effectiveness of a thermal attack.
- Privilege tools to combine lock modes (PIN and schematics).
- Cover the display with your hand while entering the PIN code, which will generate a series of traces that are difficult to use.
- Increase the brightness of the screen, which increases the temperature of the screen and consequently reduces the effectiveness of the thermal attack.