Shamir did a talk on fax crypto in May, 1994. There is no reason that this can't be completely secure, the overlays could be one-time pads. Bill Sommerfeld posted a description of the technique to the list after he went to a presentation on the technique, I'll forward it to anybody that needs a copy. Using the same overlay multiple times, though, would make it completely insecure. I can't believe that they are recommending that that could be a possibility. thad -- Thaddeus Beier thad@hammerhead.com Technology Development 408) 286-3376 Hammerhead Productions http://www.got.net/~thad