by Steven R. Corman

CNN is re-reporting a story from Die Zeit about a treasure-trove of al-Qaeda documents and manuals found encrypted in pornographic videos.  The encryption was done using a technique call steganography.

The videos were found in the possession of Maqsood Lodin, a 22 year old Austrian and suspected al-Qaeda member.  He was detained by authorities in Berlin as be returned from a trip to Pakistan.  The documents discussed plans to attack cruise ships as a distraction while Mumbai-style attacks were initiated in Europe.  Training manuals were also found.

The information was encrypted in the frames of the videos using steganography.  This technique manipulates the least significant bit of the pixels making up digital images to store hidden information.  Changes to the picture are so subtle they are impossible to detect visually, but if someone knows the information is there and has the necessary software and passwords, they can extract the encoded information.  For example, this image

is a reproduction of one that encodes the scripts of five major plays of Shakespeare.  You can see the demo for yourself by running S-Tools.

Since a video is basically a series of digital images like this, steganography can be applied to its frames to hide huge quantities of information. A 20 minute video at 30 frames per second can hold 36,000 times as much information as is stored in the above picture.

This is not the first time there have been reports about al-Qaeda using the technique.