Re: Creating a unique ID number for a dollar

Death rays from Mars made Tim May <tcmay@got.net> write:
 
>There's a way to generate a number for any person which is unique. It is not 
>shared by anyone else on the planet.
 
It's not guaranteed unique.  First, the dollar you use may be a forgery (why 
forge a dollar?  I don't know, maybe they're practicing on low-denomination 
notes which noone ever looks at closely so they can get the twenties and 
hundreds perfect.  I have a vague memory of someone doing this with either US 
dollars or UK pound notes some time ago, motivated by the "noone would ever 
bother forging a dollar/pound, so it has to be genuine" mentality).  In 
addition you'd have to specify "US dollar" rather than just "dollar" because, 
apart from the different serial number formats, some countries will reissue 
banknotes if the originals are damaged in printing, which leads to the 
possibility of two (legitimate) notes with the same serial number being in 
circulation if the original isn't destroyed as required (I have some of these 
replacement notes for now-defunct NZ dollar and two-dollar notes stashed away 
somewhere).  Does the US Treasury issue replacement notes if the originals are 
damaged in printing, or does it just destroy the notes and leave it at that?
 
Peter.

At 12:44 PM -0700 6/2/97, Peter Gutmann wrote:
>Death rays from Mars made Tim May <tcmay@got.net> write:
>
>>There's a way to generate a number for any person which is unique. It is not
>>shared by anyone else on the planet.
>
>It's not guaranteed unique.  First, the dollar you use may be a forgery (why
>forge a dollar?  I don't know, maybe they're practicing on low-denomination

Sure, these are all possible protocol failures. (Likewise, one could use
the number but not destroy the bill and instead pass it on, thus producing
collisions.)

Assuming the bill is not a forgery...not terribly hard to confirm,
especially if given the time likely to plan for execution of the
protocol--and assuming one follows the protocol....

(Note: costs of forgery are real. Fibers in the paper, the paper itself,
etc. I doubt it would be economical for a forger to enter the dollar bill
market. Maybe specifically to spoof the protocol, but that is guarded
against in the expected ways, e.g., by picking from a large pool of bills
at, say, a flea market or other business, by choosing a well-worn bill,
etc. Neither information-theoretically nor cryptographically secure, to be
sure, but "agorically secure," to coin a phrase.)

>somewhere).  Does the US Treasury issue replacement notes if the originals
>are
>damaged in printing, or does it just destroy the notes and leave it at that?

Don't know.

But certainly a dollar bill burned up as part of this protocol is unknown
to them, and would of course never be reprinted (print runs are obviously
done in large batches, with auto-indexing of numbers across sheets, so
"one-offs" would never be done anyway).

--Tim May



>
>Peter.


There's something wrong when I'm a felon under an increasing number of laws.
Only one response to the key grabbers is warranted: "Death to Tyrants!"
---------:---------:---------:---------:---------:---------:---------:----
Timothy C. May              | Crypto Anarchy: encryption, digital money,
tcmay@got.net  408-728-0152 | anonymous networks, digital pseudonyms, zero
W.A.S.T.E.: Corralitos, CA  | knowledge, reputations, information markets,
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On Mon, 2 Jun 1997, Tim May wrote:

> >somewhere).  Does the US Treasury issue replacement notes if the originals
> >are
> >damaged in printing, or does it just destroy the notes and leave it at that?
> 
> Don't know.
> 
> But certainly a dollar bill burned up as part of this protocol is unknown
> to them, and would of course never be reprinted (print runs are obviously
> done in large batches, with auto-indexing of numbers across sheets, so
> "one-offs" would never be done anyway).

Theoretically they will replace old currency with new currency if they can
recover 75% or some such high value of the surface area.  Carefully cut
out the serial numbers and burn only them, then turn the damaged bills
back in for replacement (or give them away for someone else to do - I
think it is another one of those felonies to intentionally deface
currency).

You could also derive a number from the absolute time and location of the
issuer with a GPS device.