by James Zjalic
The subject of authentication is important across the entire digital forensic field and we as examiners have various weapons at our disposal in which to defend against the onslaught of manipulators, liars and charlatans. Authentication is frequently amongst the first steps in creating a robust chain of custody for evidence received and can also be an investigation in and of itself. In no field is this more evident than that of audio forensics, where the ubiquitous rise in consumer audio software has caused the proliferation of attempts at the removal or editing of digital evidence.
There are various techniques within audio forensics to authenticate a recording and many are borrowed from areas such as computer and image forensics. One method that is individual to audio forensics is that of ENF or Electric Network Frequency, or as sound engineers like to refer to it: ‘hum’.