How secure are power network signature based time stamps?

A time stamp based on the power network signature called the Electrical Network Frequency (ENF) has been used by an emerging class of approaches for authenticating digital audio and video recordings in computer-to-computer communications. However, the presence of adversaries may render the time stamp insecure, and it is crucial to understand the robustness of ENF analysis against anti-forensic operations. This paper investigates possible anti-forensic operations that can remove and alter the ENF signal while trying to preserve the host signal, and develops detection methods targeting these operations. Improvements over anti-forensic operations that can circumvent the detection are also examined, for which various trade-offs are discussed. To develop an understanding of the dynamics between a forensic analyst and an adversary, an evolutionary perspective and a game-theoretical perspective are proposed, which allow for a comprehensive characterization of plausible anti-forensic strategies and countermeasures. Such an understanding has the potential to lead to more secure and reliable time stamp schemes based on ENF analysis.