When code protection questions (How to) come up on the list I tend to
spout the usual salient points, if I reply at all:
1. Code protection is not fool proof.  You should plan on providing as
much protection as you believe your product is worth, and no more.  If
your code is truly worth tens of thousands of dollars, then it may be
cheaper to break the protection and steal your code than it is to do
the development work.
2. Usual electrical methods of code protection damage the chip, and
even if you provide a consultant PIC breaker with several samples you
may not get usable data.
3. If you want to reverse engineer a chip you will probably save time
and money simply hiring a good engineer rather than trying to examine
someone else's code
4. If you've lost your sourcecode then you should have been more
careful.  Generally you put as much effort into backing up your code
as the product is worth to develop.  A weekend project may not need to
be backed up - you can easily recreate it if needed.  A project that's
taken a year to design and debug really ought to be stored in multiple
backup locations in both hard copy and electronic form.

This webpage changes many of the above points for me:
http://www.bunniestudios.com/?page_id=13

This website shows a method that a hobbyist can perform.  He has the
chips professionally decapped (about $50 per chip), masks the flash
with electrical tape, and then applies a UV light at an angle so the
light refracts and reflects under the metal shields protecting the
configuration fuses.

He reports that the electrical tape mask is not perfect, and some of
the code is damaged, but I have no doubt that someone suitably
motivated could readily apply a better mask.

In other words, effectively breaking a PIC's code protection costs
probably less than $1000 for someone without the right equipment, and
less than $200 for someone with a good lab.

I realize some here would prefer that such information not be posted
to the list.  In the past many code breakers kept their techniques
secret, and the freely available information on the internet was
limited, old, or useless.  I generally agreed - when the information
is very difficult to find it needn't be shared here.  Now that a
usable technique has been clearly explained and demonstrated without
all the usual "Buy my secrets of dubious success" I feel that it
should be widely known to all those who depend on it.

This is posted to the PIC tag.  Please change the tag if you would
like to discuss ethics or other aspects of this post unrelated to the
PIC or the process described herein.  A new topic regarding other
techniques to protect one's investment might be appropiate on EE,
unless it pertains directly to this process or the PIC and doesn't
apply to other microcontrollers.  Flames, if you are so inclined,
should go directly to me - no need to clog up the list with personal
matters.

-Adam
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