On the location-dependent quality of the sensor pattern noise and its implication in multimedia forensics

Abstract

Due to its uniqueness and potential in forensic applications, the sensor pattern noise (SPN) has drawn much attention in the digital forensic community and academia in the past few years. While much work has been done on the application of the SPN, little investigation into its characteristics has been reported in the literature. It is our intention to fill this gap by providing insight into the dependency of the SPN quality on the location in images. We have observed that the SPN components at the image periphery are distorted to the extent that when used for source camera identification, they tend to cause higher false positive rates. Empirical evidence is presented in this work. We suspect that this location-dependent SPN quality degradation has strong connection with the vignetting effect as they exhibit the same type of location-dependency. We recommend that when image blocks are to be used for forensic investigation, they should be taken from the image centre before SPN extraction is performed in order to reduce false positive rate. (6 pages)