IR Hiding: Use of Specular Reflection for Short-Wavelength-Pass-Filter Detection to Prevent Re-recording of Screen Images

We previously proposed using infrared (IR) LEDs to corrupt recorded content to prevent the re-recording of images displayed on a screen. This method is based on the difference in sensory perception between humans and devices and prevents re-recording by adding IR noise to the images displayed on the screen without it being detected by the human eye. However, it cannot prevent re-recording using digital camcorders equipped with a short wavelength pass filter to eliminate the noise. We have now improved our method by adding a simple countermeasure against such attacks. It detects IR light reflected off the filter by using the IR specular reflection properties of the filter and thereby detects re-recording using digital camcorders equipped with a short wavelength pass filter. We implemented this countermeasure by adding one of two types of IR LEDs (bullet type and chip type with lens) to our prototype re-recording prevention system, which is installed on a B3-size screen. Testing showed that this enhanced system can detect camcorders with an attached short wavelength pass filter.