And the lesser known, newer, invisible, digital watermark based version of it. Unfortunately very little information is available about that one. http://www.cl.

And the lesser known, newer, invisible, digital watermark based version of it. Unfortunately very little information is available about that one. http://www.cl.cam.ac.uk/users/sjm217/projects/currency/ http://www.cl.cam.ac.uk/users/sjm217/projects/currency/