I wanted to do a really simple obfuscation program, because I have
some plaintext data I don't want going out in plaintext.
All it does is bit flip a string of text.
Whats really interesting is the bitflip operations appear to be
occuring (free of charge) as it were. If I compile with the -O3 flag
in GCC.
Look at these results...
[EMAIL PROTECTED]:~/myapp/client$ g++ flip.cpp
[EMAIL PROTECTED]:~/myapp/client$ ./a.out "Hello World" 1000000
Started: 0
Ended: 20000
Performed 1000000 bit flips on a 4 character string in 20000 cycles
[EMAIL PROTECTED]:~/myapp/client$ g++ -O2 flip.cpp
[EMAIL PROTECTED]:~/myapp/client$ ./a.out "Hello World" 1000000
Started: 0
Ended: 0
Performed 1000000 bit flips on a 4 character string in 0 cycles
[EMAIL PROTECTED]:~/myapp/client$ g++ -O3 flip.cpp
[EMAIL PROTECTED]:~/myapp/client$ ./a.out "Hello World" 1000000
Started: 0
Ended: 0
Performed 1000000 bit flips on a 4 character string in 0 cycles
Something tells me the results are not quite right here.
For one thing, it's telling me I have a 4 character string, which is wrong,
"Hello World" is 12 characters.
Anyways after looking closely, I realized my code which was using a
sizeof(argv[1]) was in fact only flipping the first character which is
evidently 4 bytes wide.
I decided to use a std::string instead of assigning it to a char* and
I got more realistic results.
[EMAIL PROTECTED]:~/myapp/client$ g++ flip.cpp
[EMAIL PROTECTED]:~/myapp/client$ ./a.out "Hello World" 1000000
Started: 0
Ended: 460000
Performed 1000000 bit flips on a 11 byte string in 460000 cycles
[EMAIL PROTECTED]:~/myapp/client$ g++ -O3 flip.cpp
[EMAIL PROTECTED]:~/myapp/client$ ./a.out "Hello World" 1000000
Started: 0
Ended: 70000
Performed 1000000 bit flips on a 11 byte string in 70000 cycles
What seems strange though is optimization aside, it still looks to me
like I'm getting something for nothing here. I mean 1,000,000 * 11
bit flips should take at least 1,000,000 operations to do and in fact
my common sense tells me that I should be looking at 11,000,000 at a
minimum.
Anyways here's the code for the application if anyone is interested in
trying to replicate this.
#include <iostream>
#include <time.h>
int main(int agc, char *argv[]){
int x = 0,y = 0, count = atoi(argv[2]);
std::string s = argv[1];
clock_t start = clock();
while(x++ < count){
//std::cout << x << std::endl;
while(y < s.length()){
~s[y++];
}
y = 0;
}
clock_t end = clock();
std::cout << "Started: " << start << "\nEnded: " << end
<< "\nPerformed "<< count << " bit flips on a " << s.length()
<< " byte string in " << difftime(end,start) << " cycles" << std::endl;
return(0);
}
Thanks in advance for any info!
Regards,
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