At 4:34 PM 3/31/96, jim bell wrote:
At 11:59 PM 3/30/96 -0800, Mike Duvos wrote:
Perhaps our resident VLSI and Alpha Particle expert, Timothy C. May, could give us a guess as to whether Perry's "Nasty Mechanism" is more or less likely than Maxwell's "Daemon."
I wrote a reply to this, about decoder cloning and fingerprinting, but my Mac froze up for some reason...must be a message. Maybe I'll rewrite it... Then I saw this comment, and my sense of irony was triggered:
I don't know what Tim May will tell you, but over 10 years ago a technology was developed which is something like a scanning electron microscope, however with very low beam energies and is designed to be able to scan a chip and quantitatively measure the voltage at various/all points on the chip. It can be thwarted by a thick coating on the chip, but most organic coatings can be removed with a "plasma asher," a chamber designed to remove photoresist coatings on chips.
I wrote a paper on this, "Dynamic Fault Imaging," using voltage contrast combined with image processing and chip data bases to locate the origins of glitches and faults in microprocessors. However, voltage contrast is a lot older than 10 years, and was in use in the early 70s--my group just developed a kind of "time machine" for watching the propagation of defective states inside complex logic devices. Using such methods to look at the internal state of logic or memory devices is incredibly difficult, though a sufficiently determined analyst might discover some interesting things. (Check the archives for several articles I've written on tamper-resistant and tamper-responding hardware.) Hardware fingerprinting is an economic win over reverse-engineering analysis to the extent that it costs a huge amount more to get a particular key than the value of what's in the key. --Tim May Boycott "Big Brother Inside" software! We got computers, we're tapping phone lines, we know that that ain't allowed. ---------:---------:---------:---------:---------:---------:---------:---- Timothy C. May | Crypto Anarchy: encryption, digital money, tcmay@got.net 408-728-0152 | anonymous networks, digital pseudonyms, zero W.A.S.T.E.: Corralitos, CA | knowledge, reputations, information markets, Higher Power: 2^756839 - 1 | black markets, collapse of governments. "National borders aren't even speed bumps on the information superhighway."