AVP has a long history of working with digital audiovisual content. We recognize the inherent power of video for documenting history and for revealing a reviewable record of an event. We also recognize the dangers that video brings, i.e., it is itself always one viewpoint/perspective on an event because it sees from one vantage point only; it can be manipulated to retell an event; it may tell only the story of the entity holding the camera; it can quickly erase the privacy of the innocent). As a result of these experiences, AVP developed an interest in forensic techniques to verify the authenticity (or veracity) of digital audiovisual files from a binary perspective, instead of a content-based perspective, i.e., evaluating the file as a digital object in order to understand its history.
In 2016, we were asked by the Forensic Audio, Video, and Image Analysis Unit (FAVIAU) of the Federal Bureau of Investigation (FBI) to help with new challenges that were arising in their work with Internet Crimes Against Children (ICAC) and Child Sexual Abuse Material (CSAM). In these areas of activity, evidence is largely digital video and the examiners were interested in developing a stronger capacity to answer specific questions about digital video evidence of such crimes: 1) has this video been edited or tampered with; 2) is this video real; and 3) what device created this video?
AVP took these questions seriously and worked with FAVIAU to develop training for examiners that would help answer these exact questions. Over the course of 2016 and 2017, AVP provided four 2-day training sessions with FAVIAU examiners.
The outcome of these training sessions led to a request by FAVIAU to translate the manual methodologies we developed into an automated software product that would be able to be used by ICAC and CSAM investigators without requiring in-depth digital forensics training to produce a report on the three questions noted above.
AVP has continued to develop this software tool, now called Medex, and is focused on opening it to a wider audience to assist with any group who has questions about the authenticity or veracity of a digital video file, or any group who needs to verify that a digital video has not been manipulated. AVP’s offering of this technology is guided by thoughtful work in the realms of Journalism (e.g., Meedan), Human Rights (e.g, WITNESS), Public Safety (e.g., International ISAO Network), and Criminal Justice (e.g., Scientific Working Group on Digital Evidence, and Zero Abuse Project).
Medex does not conduct content analysis (i.e., it does not carry out facial recognition, image analysis, or audio analysis) and does not store a copy of the video. It parses the underlying binary structures that constitute the multimedia file and stores this information in an XML document that is ultimately written to the Medex database. The focus of Medex is to review the internal structures of the video file and to report on the following: is the structure valid with regard to the purported file format specification; are there any structures that have been visibly altered or modified; and does the combination of structure and metadata elements resemble that of any known camera models or software programs that can be used to create and/or edit video