Validating Phase Discontinuity as Authentication Indicator


Validating Phase Discontinuity as Authentication IndicatorFocus Area: Digital and Multimedia Forensics

Description: During counterterrorism and criminal investigations, forensic examiners must often determine if audio tracks in digital recordings have been tampered with or altered. As the terrorists and criminals have gained more expertise in this area, better and more sophisticated technology is needed to identify alterations. Southwest Research Institute has developed a new forensic technique to better verify tampering or altering in audio recordings by examining phase discontinuity of various signals within the recordings. Many different tones and signals may be present on a recording. When altering and tampering occurs, some of these likely will show phase discontinuity. Likewise, when the recording has many signals which all show continuity, no tampering has likely occurred. This method can not only show if altering the recording has occurred, but it can lalso show the specific location. Additionally, a corpus of recordings was produced that includes multiple variables such as sources and levels of usable tones, noise, distortions, and confounding factors. The corpus helped determine the effects the variables have on the developed forensic techniques. The final product included the best ways to apply the techniques in forensic examinations.

Project Cost: $286,000

Project Duration: 15 months

Operational Impact: Audio recordings can be accurately and quickly analyzed to determine if they have been tampered with or altered. Additionally, the specific location can be pinpointed, which will allow for the determination of possibly what was actually changed. This could not be done previously.

Deliverable: A new forensic technique to determine when and where audio records have been tampered with or altered

Performer: Southwest Research Institute

End Users: United States Secret Service, Department of Defense, Federal Bureau of Investigation, and Intelligence Community

Transition: Dissemination to end users and publication in a scientific journal