Source camera identification using Photo Response Non-Uniformity on WhatsApp

The Photo Response Non-Uniformity pattern can be a method for identification for an individual camera and is often present in digital footage. Therefore, the PRNU-pattern is also called the fingerprint of the camera. This pattern can be extracted and used to identify the source camera with a high likelihood ratio. This can be useful in cases such as child abuse or child pornography. In this research a 2nd order (FSTV) based method is used to extract the PRNU-patterns from videos of ten different mobile phone cameras. By calculating the Peak to Correlation Energy the PRNU-patterns of the natural videos are compared to the PRNU-patterns of the reference flat field videos of each camera to identify the source camera. This has been done for the original videos and the transmitted videos by WhatsApp for Android and IOS to determine if source camera identification by using PRNU is possible when videos are transmitted by WhatsApp. Also the PRNU-patterns of the natural videos are compared to each other to determine the possibility to find out if videos originate from the same source. With most cameras tested the method provides a high likelihood ratio, however for each case a validation of the method is necessary with reference cameras of the same model and type if used in casework. With videos transmitted by the IOS version of Whatsapp the source camera identification was not possible anymore.