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PICList Thread
'Code protection'
1996\11\08@051112 by tjaart

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> >     The code protected chip returns all three nybbles of data xor-ed
> >     together in the lower nybble.
> >
> >     bit 0 is xored with bit 4 is xored with bit 8 and returned on bit 0.
> >     bit 1 is xored with bit 5 is xored with bit 9 and returned on bit 1.
> >     etc.
> >
> >     I don't think that de-scrambling these bits would be worth the effort,
> >     and the accuracy of de-scrambling would be very low.  Many different
> >     instructions can generate the same CP code.
> >

From now on, I will fill all the unused memory with random values
to make low-life software thieves's lives as difficult as possible.

Any ideas on the format (retlw's etc) ?

--
Friendly Regards

Tjaart van der Walt
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1996\11\08@121406 by Gerhard Fiedler

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At 08:23 05/11/96 +0200, Tjaart van der Walt wrote:
>> >     The code protected chip returns all three nybbles of data xor-ed
>> >     together in the lower nybble.
>
>From now on, I will fill all the unused memory with random values
>to make low-life software thieves's lives as difficult as possible.
>
>Any ideas on the format (retlw's etc) ?

How about just snippets of old (public domain) code? Seems to be most
promising for confusion...


'code protection'
1996\12\27@182457 by Nihat Dagdemir
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hello
if i use code protection on 16c84
can i delete this device after protection

1996\12\27@185900 by Gonzalo Palarea

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At 01:05 AM 12/28/95 +0200, you wrote:
>hello
>if i use code protection on 16c84
>can i delete this device after protection
>
Yes.
____________________
Gonzalo Palarea
spam_OUTchaloTakeThisOuTspaminfovia.com.gt

1996\12\27@190727 by fastfwd

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Nihat Dagdemir <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU> wrote:

> if i use code protection on 16c84 can i delete this device after
> protection

Nihat:

Yes; you can still erase and re-program a 16C84, even if you've
enabled the code-protection bit.

-Andy

=== Andrew Warren - fastfwdspamKILLspamix.netcom.com                 ===
=== Fast Forward Engineering - Vista, California          ===
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1996\12\27@194137 by Tony Matthews

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Nihat Dagdemir wrote:
>
> hello
> if i use code protection on 16c84
> can i delete this device after protection
I have done so "no problem" Tony M.

1996\12\27@211009 by Sarunas Cepulis

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Nihat Dagdemir wrote:
>
> hello
> if i use code protection on 16c84
> can i delete this device after protection
Yes.


'Code Protection'
1997\04\28@025148 by Andrew Warren
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Peter Wintulich <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU> wrote:

> >> Erasing the [Code Protect] bit after (or even together with) all
> >> the program data doesn't seem like stealing code...
> >
> >    Right, Gerhard... But how would you ensure that the bit gets
> >    erased AFTER the program data?
>
> They are doing this already by covering the protection bits with a
> UV blocking die. (This die is visable as a black stripe near pin 22
> of the 16c73a/jw package.) The reason why the chips still erase is a
> small amount of UV still gets through, of course the program memory
> is VERY BLANK by then.

   Right, Peter... That's what STARTED this discussion.  Gerhard
   thought he had a better idea for code-protection, and through
   the Socratic method, I was demonstrating to him that his idea
   was equivalent to Microchip's.

   By the way, the suggestions recently posted to the list
   (frostiug the quartz window, making the metal layer above the
   code-protect bits slightly less opaque, etc.) are all fine in
   theory, but they aren't particularly applicable to the
   real-world processes used in the manufacture of low-cost
   microcontrollers.

   If this weren't such a non-issue for me -- in total, I've
   inadvertently protected only one or two JW parts since the new
   code-protect scheme was implemented -- I'd suggest that the BEST
   place for a solution is in the software for the chip
   programmers... A simple "code-protection override" setting,
   combined with appropriate on-screen reminders that the override
   is active, would go a long way toward minimizing the problem.

   -Andy

=== Andrew Warren - EraseMEfastfwdspam_OUTspamTakeThisOuTix.netcom.com
=== Fast Forward Engineering, Vista, California
=== http://www.geocities.com/SiliconValley/2499


'Code Protection'
1998\01\31@221508 by Eric John
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This is probably a stupid question but, can you reprogram a 16f84 after
turning on the code protection?

1998\01\31@223417 by Andrew Warren

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Eric John <PICLISTspamspam_OUTMITVMA.MIT.EDU> wrote:

> can you reprogram a 16f84 after turning on the code protection?

   Yes.

   -Andy

=== Andrew Warren - @spam@fastfwdKILLspamspamix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499


'Code Protection'
1998\10\14@005301 by Jason Langenauer
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Just a quick question about the 16F84:

Does using the MPASM directive:

__CONFIG _CP_OFF etc

turn code protection off, or does it turn the code protection bit off, this
enabling code protection.

Thanks very much in advance.

Jason "Finally got the bloody programmer working" Langenauer
First Year Engineering, University of Queensland
"Anyone who's normal doesn't really achieve anything"


'Code protection'
1999\06\30@113551 by Peter Tran
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I've got a question about code protection. How can I erase a code-protected
16C65A? I left it in the UV eraser for 2 hours, but it's still not blank.
When it wasn't in the code protection mode, it took about 15 minutes to
erase.
Thank you for your help.

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1999\06\30@114215 by Jim Mand

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You have a piece of junk.  I accidentally code protected a PIC and was told
by the MCHIP tech guys that once code protected always code protected.

{Original Message removed}

1999\06\30@115246 by Francisco Armenta

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part 0 1173 bytes content-type:text/plain (decoded 7bit)

Peter
Áoppss!
Time ago i pass for the same problem, the solution: buy another PIC, you can't
erase the PIC, in the datasheet of the PIC talk about of this issue.
My condolence, but this is the hard way of learn the importance of read first
"the Data Book" (i pass for this too)
Regards
Francisco Armenta

Peter Tran wrote:

{Quote hidden}

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name="briones.vcf"
Content-Description: Card for Francisco Armenta
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filename="briones.vcf"
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Attachment converted: wonderland:briones.vcf 2 (TEXT/CSOm) (000094A3)


'Code protection'
1999\07\01@023648 by Martin Mayr
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<x-flowed>A code-protected window-device is a really "cheap" OTP, because you can
program it only one time.

Peter Tran wrote:
>I've got a question about code protection. How can I erase a code-protected
>16C65A? I left it in the UV eraser for 2 hours, but it's still not blank.
>When it wasn't in the code protection mode, it took about 15 minutes to
>erase.


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'code protection'
2003\06\27@194548 by Matt Ancona
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How secure is the code programmed into a PIC chip?  With "code protection"
turned on, is the code truly protected or has someone somewhere figured out
how to hack into it?

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2003\06\27@203115 by Herbert Graf

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> How secure is the code programmed into a PIC chip?  With "code protection"
> turned on, is the code truly protected or has someone somewhere
> figured out
> how to hack into it?

       It is "rather" secure. It is breakable, how much it'll cost to break
depends on the part in question. Most are protected enough so that a casual
person wouldn't be able to break it (without extended effort). TTYL

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2003\06\28@164808 by Mike Morris

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There was a discussion regarding this a while back. I'd hazard to say any
code protection can be defeated given enough resources (that is, money and
time). It really boils down to how valuable your code is to someone else.
What magnitude of resources are worth investing in breaking the protection,
versus developing the code themselves.  In most cases I'd guess the built
in protection is adequate. IIRC, the old 'c84 was used in a smart card,
which prompted *lots* of effort to hack it (which succeeded) due to the
gains breaking the protection would yield.

So evaluate the value of your code. If you are paranoid, make the pic
difficult to identify (remove part numbers, etc.), or even better, make it
mechanically difficult to get to (ie, potting).

- Mike

At 07:43 PM 6/27/2003 -0400, you wrote:
>How secure is the code programmed into a PIC chip?  With "code protection"
>turned on, is the code truly protected or has someone somewhere figured out
>how to hack into it?
>
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'Code protection'
2004\09\28@115523 by 8859-1?Q?M=E1rcio_Barbiani?=
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Hello,

I am looking for a way to protect my product. I am thinking about loading a
bootloader and burning the pin B7.

Burn would be a 12v surge applied to this pin.

Does someone have this experience?

Thank you.


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2004\09\28@130717 by Mike Hord

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I think that would be a bad idea.  You have no way of knowing what
incidental damage 12V applied to an IO pin could cause- it may just
destroy that pin, or it may cause internal damage in some unusual
way that will only reveal itself after a thousand hours of operation.

Why not just use the code protect fuse?  I know it's not perfect, but
I think anyone who wanted what's inside the chip badly enough to
circumvent code protection would also be able to circumvent your
pin burning scheme.

Mike H.


On Tue, 28 Sep 2004 06:02:52 -0300, Márcio Barbiani <obf> wrote:
{Quote hidden}

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