Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!ucsd!brian
From: brian@ucsd.Edu (Brian Kantor)
Newsgroups: sci.electronics
Subject: Re: 2764 UVEPROM.
Message-ID: <11993@ucsd.Edu>
Date: 26 Feb 90 20:33:19 GMT
References: <2446@loral.UUCP>
Reply-To: brian@ucsd.edu (Brian Kantor)
Organization: The Avant-Garde of the Now, Ltd.
Lines: 26

In article <2446@loral.UUCP> miller@loral.UUCP (BIG DAVE) writes:
>Does anyone know a way of protecting the data that's been stored in a 2764, 
>8KX8, EPROM ?. Is there a way of safegarding data stored in such devices 
>once one gives the device to someone else ?. I read the spec sheets and found
>no provisions for 'security bits', ala PALs, so I'm curious as to how one might
>get around to solving such a problem. I would greately appreciate any help in
>this matter.

Depends on what you're trying to protect.  If you want to keep people
from duplicating the ROM, you're out of luck.  If you want people not to
be able to read the data out of the rom and use it some other way,
you can make it a little harder.

You can store your data in encrypted form, and have the decryption
performed based on a user-entered key, without which the system won't
work.  Anyone with the key has your info.

You can scramble the address and data lines, which will prevent the data
from being quite so easily read out from the raw chip, but won't stop
anyone who has access to the device it's installed in.

Essentially, because any piece of hardware is a closed system, outside
of autodestruct mechanisms there is nothing you can do to stop someone
who is determined enough from figuring out how it works.  All you can do
is make it cost them more.
	- Brian