From: tcmay@netcom.com (Timothy C. May)
Date: Mon, 5 Sep 94 15:00:56 PDT
To: rarachel@prism.poly.edu
Subject: Re: Art Gallery on internet needs PGP signatures
In-Reply-To: <Pine.3.05.9409051558.A4926-c100000@prism.poly.edu>
Message-ID: <199409052200.PAA15039@netcom14.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



 Arsen Ray A. wrote:

> Now the question I have is what if the forgery is done so well, would it
> fool the scanner and pass the signature?  ie: What if you take a picture
> of the painting or part or whatever using high resolution film, etc. 
> Would it pass the signature?

I don't know (but I'll make some speculative/engineering guesses), as
I never saw the system...like I said, I heard a verbal description of
it some years back (from Jim Omura, of Cylink, now famous for suing RSADSI).

First, photo-reproduced art is almost never confused with the real
thing. Surface texture, brush strokes, light at different angles, etc.

Second, I could imagine the scanner system using light at two or more
angles specifically to provide better protection against forgeries.

(In the intended main applicaiton, that of detecting machine part
forgeries, the pattern of natural scratches and abrasions, and
grains/regions in the metal, would be essentially impossible to
mechanically reproduce. Not completely impossible, but very difficult,
and hence not cost-effective.)

Anyone interested in pursuing this may be find out if Light Signatures
still exists. Omura may know, and someone at RSADSI probably would
have records of their licensing arrangements.

--Tim May

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