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 --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]