27 Jan
2006
27 Jan
'06
1:08 p.m.
OK genius, you suggest something that NO ONE can break! I'm sure the
CIA, FBI, MI-5 and the Mafia would all love to know about it.
Joe
At 12:00 AM 1/28/06 +0000, you wrote:
(and contents)
when it was removed from the circuit. Or else redisign and
use a PAL or some form or programmable logic that has a security fuse to
prevent it from being read.
Oh come on. PALs are about as secure as a cardboard front door.
If you're going to allow unpackaging the chip, then remember that PAls
used the old fusible-link technology. And those links will be in the top
metalisation layer. You could see which ones were intact and which were
blown with a microscope. And I guess if you could open up a new example
of the same make and type of PAL without damaging it, you could blow the
links one at a time and keep on looking at the chip to work out which was
which.
But why go to all that trouble? Even if the security fuse is blown, it's
possible to reverse-engineer a PAL using well-known techniques of
applying various inputs and looking at the outputs. With a PAL there is
no way to have a hidden variable. Any flip-flop in the chip (wether part
of thr 'R' of a registered PAL, or made from the AND/OR matrix) will
appear on one of the pins (this is not true of GALs, unfortunately). So
with a PAL it's relatively easy to work out what's going on.
-tony