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From: davidc@vlsisj.VLSI.COM (David Chapman)
Newsgroups: comp.lsi
Subject: Re: A Truly Secure (tm) ROM access
Message-ID: <15589@vlsisj.VLSI.COM>
Date: 1 Jun 90 05:18:19 GMT
References: <39144@mips.mips.COM>
Reply-To: davidc@vlsisj.UUCP (David Chapman)
Organization: VLSI Technology Inc., San Jose, CA
Lines: 28

In article <39144@mips.mips.COM> mark@mips.COM (Mark G. Johnson) writes:
>There was an EPROM built which was indeed secure.  It was the Intel
>...
>Also, I recommend talking to your favorite IC engineer and asking

You rang?  :-)

>the question "Suppose I want to use microprobes to discern the logic
>states on 64 different signals of a chip, and suppose those signals
>don't connect to the metal layer.  How easy and/or costly would this be,
>and how many samples (chips) would be required?"

I'd say 1 chip and not that expensive.  All you need is the Schlumberger
E-beam prober.  Assuming that the E-beam won't erase your EPROM (and I
don't know the answer to that one), you can read the signals directly
off the chip.  Chip designers love them; they can compare the signals
on the chip with their simulations (we have one, and I'm told it works
like a charm)!

No physical probing is necessary.

P.S.  "Not that expensive" is marginal cost; the prober itself is $500K,
      I think.
-- 
		David Chapman

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