Japanese firm Fujitsu is pushing a technology that can encode data into a picture that is invisible to the human eye but can be decoded by a mobile phone with a camera....The technique stems from a 2,500-year-old practice called steganography, which saw the Greeks sending warnings of attacks on wooden tablets and then covering them in wax and tattooing messages on shaved heads that were then covered by the regrowth of hair.

Childhood's End

The group of artists and scientists that had so far done least was the one that had attracted the greatest interest -- and the greatest alarm. This was the team working on "total identification." The history of cinema gave the clue to their actions. First, sound, then color, then stereoscopy, then Cinerama, had made the old "moving pictures" more and more like reality itself. Where was the end of the story? Surely, the final stage would be reached when the audience forgot it was an audience, and became part of the action. To achieve this would involve stimulation of all the senses, and perhaps hypnosis as well, but many believed it to be practical. When the goal was attained, there would be an enormous enrichment of human experience. A man could become -- for a while at least -- any other person, and could take part in any conceivable adventure, real or imaginary. He could even be a plant or an animal, if it proved possible to capture and record the sense impressions of other living creatures. And when the "program" was over he would have acquired a memory as vivid as any experience in his actual life -- indeed, indistinguishable from life itself.