grinding down chips was Re: QX10 graphics board

[Joe R.]

   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
>