I had a pretty cool experience while giving a LiveMeeting demonstration of digital watermarking. In this demonstration I was showing a prospective customer how robust the digital watermark really is and how we can make it work within a PDF document. The procedure started off with digitally watermarking an image and using it in the construction of a PDF. What I demonstrated next was how the watermark would persist if someone took a "screen grab" of the actual document. The PDF was open in Adobe Acrobat and I proceeded to use a third party utility to "screen capture" just the PDF document from the screen...

Keep in mind that I am sharing my entire desktop for all Live Meeting attendees to see. Next I opened the captured image in Photoshop and then showed how the watermark was recovered. I also did some down-sampling and cropping of the screen capture and showed that we could still recover the watermark. Everyone was very impressed, but what happened next was even more exciting. 

One of the security folks on the call posed this question: "What if I took a picture of the screen capture with my camera? I bet the watermark could not be recovered then." I answered the question by explaining that it technically can be achieved but there are so many variables that come into play, like lighting, skew, resolution, blur, and distance from the screen. It didn’t matter; the security expert had already taken a snapshot with his camera and sent the image to me to try. He took a snapshot that he believed still maintained legibility. I received the email before I even completed my explanation about how the watermark could or could not be recovered. When I opened his snapshot, I saw his monitor displaying my desktop at a slightly skewed angle, and it was a fairly dark image. The PDF image was only a portion of the snapshot. I have always had high confidence in our technology, but when I saw this snapshot, slightly skewed in low lighting, I was not optimistic about being able to recover the watermark.  Oh well, I gulped and attempted to read it LIVE on the spot, in front of my audience. 

Guess what?! The watermark was recovered. Now that was very impressive, to the customer and to myself.

Below is a reduced version of the screenshot that I worked with, and is not meant to be read. A photo of another person's monitor, displaying the contents of my monitor, displaying a PDF, and the digital watermark was embedded in the PDF, and the watermark still came through!

Certain portions of this image have been blurred to protect the confidentiality of the user.