Jason Dawes wrote:
> No matter what scheme you use, it's not hard to break it if you have those
> basic assembly skills. You can have the most wonderful self-modifying code
> in existance, but once it's done modifying itself, it can be pulled out of
> memory. The checksum traps (elsewhere in the application I assume) help
> somewhat, but hell - all they are is comparisons.
The whole idea here is to give crackers some work. Expressing myself in good
terms, the idea here is to give them so much work that, by the time they
finally crack the software theyr vision will be down by 60% :-)
Now seriously. My two ideas are a little bit more difficult to crack than
simple comparison change. I wasn't thinking about decifering the whole code
database at once, so it isn't really easy to just wait for the software to
decifer itself and then pull out the image and build a new pdb. Also, my
checksum traps would be probabilistic, failing some 5% of executions. This
makes tracking them more difficult, and is enough to give the cracked program
an unreliable behaviour. One note, before someone warns me, is that these traps
are tedious to write, because no two can be alike (the same assembly code), to
prevent automated search.
--
Sergio Carvalho
---------------
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If at first you don't succeed, skydiving is not for you
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