Using a program he wrote, Krawetz could print out the quantization tables in a JPEG file and determine the last tool that created the image -- that is, the make and model of the camera if the image is original or the version of Photoshop that was used to alter and re-save the image. Comparing that data to the metadata embedded in the image he could determine if the photo was original or had been re-saved or altered. Then, using error level analysis of an image he could determine what were the last parts of an image that were added or modified.It's sad that such a two-bit, backward, tin-horn outfit like Al Queda can give the world so much trouble.
Krawetz took an image from a 2006 al Qaeda video of Ayman al-Zawahiri, a senior member of the terrorist organization. The image shows al-Zawahiri sitting in front of a desk and banner with writing on it. But after conducting his error analysis Krawetz was able to determine that al-Zawahiri's image was superimposed in front of the background -- and was most likely videotaped in front of a black sheet.
07 August 2007
The Pixels Do Not Lie
If an entire diseased tribe lives and dies by 6th-century violence and culture you really can't expect them to grasp the subtleties of modern digital video production, can you?