[11753] in cryptography@c2.net mail archive
Re: unforgeable optical tokens?
daemon@ATHENA.MIT.EDU (Arnold G. Reinhold)
Tue Sep 24 23:03:20 2002
In-Reply-To: <8765x0skz9.fsf@snark.piermont.com>
Date: Tue, 24 Sep 2002 22:47:52 -0400
To: cryptography@wasabisystems.com
From: "Arnold G. Reinhold" <reinhold@world.std.com>
It might be possible to get the same effect using a conventional
silicon chip. I have in mind a large analog circuit, something like a
multi-stage neural network. Random defects would be induced, either
in the crystal growing process or by exposing the wafer at one or
more stages with a spray of pellets or chemicals. The effect would be
to cut wires and alter component values such as resistances, zener
diode break down voltages, transistor gains.
Critical parts of the circuit would be protected by a passivation
layer or would simply designed with larger geometries to make them
less sensitive. Multiple inputs would be driven by D/A converters,
either in parallel or through a charge coupled analog shift register.
There would be enough "stuff' in the middle to make it impractical to
characterize the entire circuit from the inputs. One could use very
small geometries for the network and still get high circuit yield
since defects are something we want.
The advantage of this approach over a optical system is that it would
be very easy to interface with existing technology -- smart cards, RF
ID, dongles, etc.
Arnold Reinhold
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