D.C. Williams wrote: | With barcoding as the standard, another person prints his key on a small | unmarked card and hides it somewhere deemed to be secure by him. The | UPC-label attack fails because his keyring isn't disguised as UPC product | labels. How does the attacker know what to look for? | | True Paranoids could devise some sort of "invisible ink" method, | requiring UV or heat exposure before the barcode becomes visible. | Now your backup key looks like a blank sheet of paper. ;-) Picking a few nits: Putting the UPC's on things other than cards (such as books) makes it easier to hide in the open. `UPC' stickers on, say, a few books are easier to miss than UPC stickers on index cards. Invisible ink draws attention to the correct UPC's once they know you're using it. See Kahn for a discussion of secret inks being developed during the second world war. If you want to hide bits, they should be stripped of low entropy parts and hidden with a stego program. Adam -- "It is seldom that liberty of any kind is lost all at once." -Hume