Saturday, September 08 2007 @ 09:48 AM CEST Contributed by: ColdT Views: 21758
This essay consists of a CRC tutorial and a way of how to reverse it. Many
Coders/Reversers don't know exactly how CRC works and almost no one knows how to
reverse it, while this knowledge could be very usefull.
First the tutorial will
learn you how to calculate CRC in general, you can use it as data/code
protection. Second, the reverse part will learn you (mainly) how to reverse
CRC-32, you can use this to break certain CRC protections in programs or over
programs (like anti-virus).
There seem to be utilities who can 'correct' CRCs
for you, but I doubt they also explain what they're doing.
I'd like to warn you, since there is quite some math used in this essay. This
wont harm anyone, and will be well understood by the avarage Reverser or Coder.
Why? Well. If you dont know why math is used in CRC, I suggest that you click
that button with a X at the top-right of this screen. So I assume the reader has knowledge of binair arithmetic.
Friday, February 09 2007 @ 01:33 PM CET Contributed by: Devoney Views: 21017
Level : newbie
You all probably know about the windows file protection? No? Let me explain. The files in the directory system32(or system) are critical for windows. Therefore, windows has it own file protection system managed by sfc.exe. (Start -> Run -> cmd.exe -> sfc.exe and you see its parameters). This file is activate during windows. It checks if the files are the original ones, otherwise, the not original files get replaced by the original ones.