Device temporal forensics: An information theoretic approach

By formulating the problem of ordering the outputs observed from a device over time, we pose a new problem in forensics and propose a framework for addressing this problem of device temporal forensics. Our proposed framework is based on a two-stage approach wherein time-dependent device parameters are first estimated from observed outputs and the resulting estimates are then temporally ordered by employing a Markov model for the temporal evolution of device parameters and exploiting the data processing inequality in information theory. We demonstrate and evaluate a simple realization of the framework for digital camera forensics based on photo-response non-uniformity. Results obtained over a database of online images indicate that the method provides accurate temporal ordering.