Mike Harrison wrote:
> >If you want a secure part, look at the Atmel devices which scramble the
> >address and data with XOR keys that are held in volatile RAM. Opening the
> >chip clears the RAM and it is a difficult exercise to go through all possible
> >keys to try to recreate the program from the encrypted remnants.
>
> Aren't you thinking of the Dallas 5000 devices - Actually these have been hacked.

Yes I meant the Dallas devices. Commonly used on "battery cards" so
that the pirates can protect their piracy code from other pirates <G>.

The Dallas parts are much less hackable than PICs IMO.

As always it is a trade off between cost of protection vs cost of I.P. loss.
Copywrong and Patent laws are only good if you have really deep pockets so you
can afford enforce your rights. And by the time you get your infringer into
court the market will have changed. And a lot of countries have very poor
law for protecting intellectual property (I.P.), so you basically have to sell
as many devices as you can, as quickly as you can, then get out when the knock
off's appear.

> There is a very interesting article describing this and other hardware security issues here :

> http://www.cl.cam.ac.uk/~mgk25/tamper.pdf

A "Must read" for anyone considering code protection. Again, many ways to
secure the cat.

R

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