unforgeable optical tokens?

[Marc Branchaud]

Perry E. Metzger wrote:
> 
> But if you can't simulate the system, that implies that the challenger
> has to have stored the challenge-response pairs because he can't just
> generate them, right? That means that only finitely many are likely to
> be stored. Or was this thought of too?

According to the article at http://www.msnbc.com/news/810083.asp :

   “We have about a terabit — a one followed by twelve zeros — of
   information contained in a penny’s worth of material,” said
   Gershenfeld.
   ...
   In practice, the combination of laser light inputs and resulting
   speckle pattern outputs for each token could be stored on a secure
   database. The token could then be read at a terminal that queries
   the database and authenticates the token’s identity.

I don't know just how practical this would be, in practice...

BTW, I think the Science article cited in the above article & on Pappu's
web site is available to Science subscribers (of which I'm not) at

http://www.sciencemag.org/cgi/search?volume=&firstpage=&author1=Gershenfeld%2C+N&author2=Pappu%2C+R&titleabstract=&fulltext=&fmonth=Oct&fyear=1995&tmonth=Sep&tyear=2002&hits=10&sendit.x=30&sendit.y=6&sendit=Search

(The above URL may have been munged...)

		M.


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