Avoid copy Eprom.

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Hi,

I have program in an Eprom 27C256,
and I want avoid copies of this Eprom.
Is there a way to disable coping?

Thanks,
S.L.


Re: Avoid copy Eprom.

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No. If the CPU can read from it, by manipulating
its buses, then so can anything else.

You could, though, scramble the address and
data lines, so that the PCB wiring automatically
corrects things. This won't work if the potential
copier has access to the circuit board.

You want to use a more modern secure microcontroler,
which avoids having open buses between the CPU and
EPROM.

Richard [in PE12]



Re: Avoid copy Eprom.
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I don't see how. If you prevented anyone from reading the data, you'd
also prevent your processor from using the chip.

You could possibly try encryption or other some other obfusciation
method but that wouldn't stop a serious attacker. You might be better
off using a uC with onboard flash and enabling the code protection. That
could also be bypassed but it takes alot more effort.

How valuble is your data?

Al

Re: Avoid copy Eprom.
I have made some changes to a program for a Z80 processor,
and I sell a machine with this modification.

There are some person that read my Eprom and
sell the same machine with my modification.

So the only thing is to avoid the reading.


Re: Avoid copy Eprom.

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How hard is this modification to reverse engineer?

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There is no point in stopping someone from stealing
your copyright, if they can just implement the same
change themself in a few days.

tim



Re: Avoid copy Eprom.
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That's been my thought for a while. There does seem to be an
inordinate amount of paranoia regarding protecting code that's
hardly worth protecting, since it can be reimplemented with
less effort than copying. I know, I know, there are exceptions.

That said, there are some people in this world (the other side
of the world from me) that will spend more effort copying than
reimplementing - and that may be the point. Make it very difficult
to copy, and your knockoffs will be later and later to market.

And while you're at it, post full schematics with some errors
inserted, and post full source with some errors included, and
the knockoffs may never make it to market.

I have seen this done before (not with electronics or code),
and the results were hilarious.



Re: Avoid copy Eprom.
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... snip ...
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Electrolytic capacitors in the recent past, and the results were
not exactly hilarious.

--
Some useful references about C:
  <http://www.ungerhu.com/jxh/clc.welcome.txt
We've slightly trimmed the long signature. Click to see the full one.
Re: Avoid copy Eprom.
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Are you implying that the party(ies) who inserted bogus specs into
whatever documents were involved have some culpability? I don't know
any specfics about this episode.


Re: Avoid copy Eprom.
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That seems to be a general principle in academia and the arts -- the people
with the most fear of having their ideas stolen are those who don't have a
lot of really good ideas.

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*chuckle*



Re: Avoid copy Eprom.

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Another trick you can do is include some random data in the eprom, which has no
purpose. That way
you can easily prove if someone has copied your device.
If the product has a suitable user interface, a good trick is to have a secret
'hidden' function,
e.g. a combination of keys, that displays your name etc., from text that is
encrypted in your eprom
so it's not obvious to the casual observer looking at the contents.
This makes it even easier to prove an anauthorised copy.


Re: Avoid copy Eprom.

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Can you remove the Z80 and perhaps replace it with
one with on-board secure flash, and put the
program in that, instead of in EPROM.

You could try using potting compound to prevent either
the processor or EPROM being removed, and/or
things attached to its pins.

Richard [in PE12]



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Re: Avoid copy Eprom.

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The only way to protect it would be to add some other hard-to-copy hardware like
a PLD or
microcontroller to the system - either to some available port, or by putting the
eprom on a small
PCB with additional hardware that the hardware uses for authentication.
This is common practice in the automobile ECU re-tuning industry.


Re: Avoid copy Eprom.
|> The only way to protect it would be to add some other hard-to-copy
|> hardware like a PLD or microcontroller to the system - either to some
|> available port, or by putting the eprom on a small PCB with additional
|> hardware that the hardware uses for authentication.

Why copy the dongle if you can remove the dongle routines?

That would require, of course, some significant amount of reverse
engineering (depending on the dongle quality), but still it doesn't
keep people from copying if they really want to.

Rainer


Re: Avoid copy Eprom.
On Thu, 9 Jun 2005 11:35:05 +0000 (UTC), snipped-for-privacy@atbode100.lrr.in.tum.de (Rainer

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Nothing is 100% secure. You just need to decide how much effort a potential
copier is able/willing
to put in. Adding a properly-implemented dongle solution increases the skill
level required to copy
by a substantial amount.
 In some cases it is also possible to hide important algorithms, keys etc.
inside a dongle to make
it very hard to remove..

Re: Avoid copy Eprom.
snipped-for-privacy@hotmail.com writes:
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Yes.  If you break the pins off the package, it will be much more
difficult for someone to copy it.

Re: Avoid copy Eprom.
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LOL! The only answer so far that has gotten close to answering the OP's
question directly. No amount of encryption or obfuscation can protect an
Eprom from being copied, as every bit of every byte is accessible. Just
as photos cannot be copy protected as anyone can run them through a
scanner etc. But I think that the OP should really of asked "how do I
make it harder to for someone to make a working copy of my system" or
suchlike.

The answer lies in adding an extra bit of hardware and having the
program verify it. What comes to mind is a suitably programmed secure
micro in an small package that can easily be added to the system,
perhaps through a single I/O pin. It could even be powered from the same
pin! The program needs to verify that the device is attached and that
it's response meets the challenge given.

So yes, the Eprom can still be copied but it won't work unless they
crack the secure device or the Eprom code and overcome the basic
security measure. But that's work they mightn't be up to hopefully.

my2cents
*Peter*

Re: Avoid copy Eprom.
On Fri, 10 Jun 2005 08:51:45 +1000, Peter Jakacki


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   It's not that hard to disassemble the EPROM code to see how it
accesses the "secure device" and see what it expects back from it. It
would be better to encrypt everything in the EPROM and have the
"secure device" hold the key for decryption. But presumably all code
runs from the EPROM, the boot code will have to be 'clear' and decrypt
other areas (or the whole EPROM) into RAM and then execute the code
segment from RAM. This becomes a significant effort for only a mild
amount of security. A determined individual or group WILL disassemble
all the code if they can get to the object code.

   It would be much better to have a processor that has its code
memory completely internal on the chip, and has a 'security' bit that
keeps the internal memory from being (easily) read.
   This was already posted:

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   Are there Z80-compatible microcontrollers? I've heard of the
Rabbit, with a superset of the Z-80, but I'm not really familiar with
it.

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-----
http://mindspring.com/~benbradley

Re: Avoid copy Eprom.
To disassemble an Eprom requires knowledge, time, and effort. Using a
secure device just makes it that much harder then COPY,BURN. You or I
plus many others would be able to hack the system, but then again, why
would we when we can just design a new system anyway. This is only a
basic security mechanism and any determined hacker will eventually
overcome it no matter how secure it is made.

The OP is working with an existing design so I guess he doesn't have an
option of using some other cpu with on-board flash. Anyway, he may be
more of a software guy and not all that keen to delve into the hw.

*Peter*

Ben Bradley wrote:
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Re: Avoid copy Eprom.
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Try Zilog?  http://www.zilog.com/products/family.asp?fam22%6
They have Flash models ( but not likely to plug into an existing Z80
design, unless you make an adaptor ) - maybe Zilog could do a
eZ80_BGA => StdZ80 module ?

IIRC std Z80's do not have Adr latch, but another scheme to give medium
security is to replace the Latch with a PLD, that scrambles the adr
lines, and adds some state logic.

-jg


Re: Avoid copy Eprom.
The machine is build by a company, I only have made the change to
Eprom,
and I sell this Eprom to the person that have this kind of machine.

This machine have 3x8 DIP swicth, I can make a function to validate a
combination
of an unused swicht. This can stop the machine if I want.

Thanks,
S.L.


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