Creating a unique ID number for a dollar

[Peter Gutmann]

Death rays from Mars made Tim May <tcmay at 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.