Recent advances on image processing techniques allow identification of which device has taken a given picture, and allow a match with those contained in social network accounts (Facebook, Flickr, etc.). This possibility has been demonstrated in a recent JRC study that received the Best Paper Award at the International Conference on Computer Vision Theory and Applications (VISAPP 2014) in Lisbon this January.
With the widespread diffusion of photo sharing through the so-called social networks, a considerable amount of new digital images is flooding the internet every day. These images constitute visual 'traces' of people’s lives and interests. Unfortunately, these contents can often be easily accessed by others; in fact, many social networks are not privacy-friendly by default, people need to explicitly set privacy constraints. On the other and, under the proper legal framework and in specific conditions, law enforcement bodies can be entitled to access such data, if relevant, for investigations.
The JRC has exploited the noise pattern that is left in a digital picture by any image sensor, as a fingerprint of the imaging device (whether it is a digital camera, a smartphone, a tablet, …). Such a Sensor Pattern Noise (SPN) has been shown to be unique for every single device. This allows one to find, given a picture, a social network account containing images taken by the same camera, and in turn it can be possible to infer the identity of the camera owner.
The JRC study raises awareness of the potential threat to citizens’ privacy that these techniques may pose if malicious persons make use of them. At the same time, it shows a valuable methodology of investigation for law enforcement bodies, that may be used for example to find information on the possible creator of an image showing illegitimate content.
The JRC’s research on this topic will continue to explore the usage of the Sensor Pattern Noise for helping law enforcement investigations. Capabilities such as verifying whether a given image has actually been taken by a given camera, identify which camera among a set has taken a given photo, or separate a given set of photos in different clusters with respect to the source camera, are all potentially precious in the forensic field, and will be thoroughly investigated by the JRC, with the ultimate aim to offer new tools for investigation to the European police forces, including the European Cyber Crime Centre.