A Review of Electrical Network Frequency (ENF) Based Applications in Media Forensics

Electricity network frequency (ENF) is the frequency of electrical voltage transmitted by power distribution lines, with a nominal value of 50 Hz in most of the world and a nominal value of 60 Hz in the vast majority of America. The ENF makes continuous oscillations within certain limits around the nominal value depending on the supply-demand power imbalance in the network. These time-dependent changes in ENF are called the ENF signal. Although the ENF signal may show similarities in short time intervals, it becomes unique in large time intervals. The ENF signal is intrinsically integrated into audio and video recordings under certain conditions. The fact that the ENF signal shows different characteristics in different networks and is unique depending on time allows researchers to make inferences about the file content integrity, together with the location and time information of the audio and video files. In this study, it is discussed how to detect modifications in the file content and metadata using ENF within the scope of ENF-based forensic analysis of audio and video. In this context, existing ENF applications in the literature and the potential ENF usage areas are examined and analyzed.