Hal,

Those slides show a efuse that is really blown. The new technology does
not vaporize the poly, it EM moves the ions all to one end, changing the
poly's behavior under polarized light. But, the method still applies:
you can visually read the values.

Thanks for the posting.

Austin

Hal Murray wrote:
>> Yes, it is that cheap (and easy) to find and read efuses. If they had
>> used Actel's via fuse technology, it would be much, much harder, but
>> still do-able for a small number of vias. Of course, you would have to
>> know where to look. The poly efuse is huge, and is almost big enough to
>> see with the eye. An array of 128, or 256 has a big sign on it: "efuse
>> array right here!"
>
> Whenever I get involved with a discussion like this, I point people
> at these papers:
> http://www.cl.cam.ac.uk/~mgk25/sc99-tamper.pdf
> http://www.cl.cam.ac.uk/~mgk25/sc99-tamper-slides.pdf
>
> That's from 1999. Still a great read.
>
> The details have changed, but I doubt if the general idea is out of
> date. People who build chips have to debug them. They will keep the
> technology up to date.
>