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Old 06-10-2007, 05:50 PM
mathematica_analytica
Posts: n/a
[SOLVED] Write a program is assembly language in which the contents of an input

file called indata.txt are read ......? one character at a time and then passed through inline assembly instructions that rotate each character three bits (encryption part). The encrypted version is saved in a new file called newdata.txt. The decryption program reverses this step, displaying the original file on the monitor.
a) Be creative and write your own complex encryption in-line assembly code based on 16 bits (two bytes at a time , if number is odd , the last byte should be handled differently). You should do this by first storing the contents of the original file in an array (in C++), and then mix-up the bits (in in-line Assembly) in a way that you can get it back. However , your steps should be complex enough that one cannot see an easy pattern.

b) Hand-write all the general steps. For example, "swapping bits 2 and 3 of every other character" is considered a general step.

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  #2 (permalink)  
Old 06-10-2007, 05:56 PM
Fred
Posts: n/a
Do your own homework, dude. I'll give you a little hint.

#include <fstream>
using namespace std;

int main()
{
ifstream infile("indata.txt", ios::in | ios::binary);
ofstream outfile("outdata.txt", ios::out || ios::binary);
char temp;

while(infile)
{
infile.get(temp);
__asm
{
mov bl, temp
rol bl, 3
mov temp, bl
}
outfile.put(temp);
}

infile.close();
outfile.close();
}

That's the encryption part. use ror operator for decryption part. good luck.

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