Re: Making C compiler generate obfuscated code

On 12/16/2010 03:52 AM, glen herrmannsfeldt wrote:
> Torben Fgidius Mogensen<torbenm@diku.dk> wrote:
> (snip on object code obfuscating compilers)
>
>> Indeed. I wsa not impressed by the approach: It made the code a lot
>> larger and a lot slower and the obfuscation was easy to remove.
>> Ideally, obfuscated code should only be marginally larger and slower
>> than "normal" code, but extremely difficult to reverse-engineer.
>
> It would seem that one could divide the code into blocks at
> unconditional branches, and then move the blocks around randomly.
> Though again, it might not be hard to unobfuscate. I do remember
> stories about compilers with optimization algorithms based on
> random numbers and the natural difficulty with reverse engineering.


My decompiler worked by turning the disassembled code into a graph
(also removing unconditional jumps in the process), so the actual
location of hunks did not make when whit of difference.


> That is, assuming such tricks are allowed. As I understand it
> (possibly incorrectly) the exception model in Java makes it
> difficult to do many optimizations that traditionally would have
> been done. Moving statements outside of loops, for one.


Java does make guarantees about apparent execution order, but to the
degree that you know that statements are not going to cause "side
effects", you can reorder stuff.


--
Beware of bugs in the above code; I have only proved it correct, not
tried it. -- Donald E. Knuth

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