Abstract
The Electric Network Frequency (ENF) is a signature of power
distribution networks that can be captured by multimedia recordings made
in areas where there is electrical activity. This has led to an
emergence of several forensic applications based on the use of the ENF
signature. Examples of such applications include estimating or verifying
the time-of-recording of a media signal and inferring the power grid
associated with the location in which the media signal was recorded. In
this paper, we carry out a feasibility study to examine the possibility
of using embedded ENF traces to pinpoint the location-of-recording of a
signal within a power grid. In this study, we demonstrate that it is
possible to pinpoint the location-of-recording to a certain geographical
resolution using power signal recordings containing strong ENF traces.
To this purpose, a high-passed version of an ENF signal is extracted and
it is demonstrated that the correlation between two such signals,
extracted from recordings made in different geographical locations
within the same grid, decreases as the distance between the recording
locations increases. We harness this property of correlation in the ENF
signals to propose trilateration based localization methods, which
pinpoint the unknown location of a recording while using some known
recording locations as anchor locations. We also discuss the challenges
that need to be overcome in order to extend this work to using ENF
traces in noisier audio/video recordings for such fine localization
purposes.