Many years ago I posted an idea of mine about cryptographic physical
watermarking of things, such as paper money, or maybe missiles. Whatnot.
The idea was that you'd do some chaotic physical process in order to lay
down a physical watermark, then image it, and finally digitally sign
what was seen via asymmmetric cryptography. I imagined you'd then print
the signature "on the bill" as a 2D barcode, to be verified. But I never
worked out how you would deal with the inevitable "broken bill". I
thought it'd take some kind of high end error correcting code.
Now it finally came to me you don't need that at all. Instead, just
repeat what you imaged from the bill, on the bill, verbatim, using
whatever level of ECC you want, and then the signature. The verifier can
utilize the digital, error corrected replica for hard crypto purposes,
while separately verifying that it matches -- in any soft statistical
knee -- a hard to mechanically replicate, unique signature, embedded in
the "bill".
My first and best idea about how to make this physical nonce is to mix a
couple of dozen well cut differently fluorescent plastic fibers into the
paper or plastic fiber pulp from which the bill/artifact is made. It
would be rather difficult to replicate such a random arrangement of many
fibers over, say, a 1200dpi scanned bill. Especially if the highest end
scanner interferometrically made sure, that the fibers/chaff really are
embedded in the paper, instead of having been printed on it.
Any problems with my idea? I'd like to hear, especially since it has
been a couple of decades coming.
--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-40-3751464, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
