The photo response non-uniformity (PRNU) of a sensor can be useful to enhance a biometric systems security by ensuring the authenticity and integrity of images acquired with a biometric sensor, e.g. by performing a source device identification. Previous studies regarding the feasibility of this application have been conducted on the CASIA-Iris V4 database by studying the differentiability of the sensors PRNU fingerprints. The results showed a high variation among the different subsets of the database.
It was assumed that this high variation could either be caused by correlated data or that different sensors may have been used for the acquisition of the subsets. To investigate the latter case we perform a forensic investigation on the CASIA-Iris V4 database, since there is no specific documentation on the number of sensors used for the acquisition. We apply an existing forensic technique and we propose several novel forensic techniques to establish a ground truth of how many sensors have been used to a acquire a digital image data set in a blind manner and without any a priori knowledge.