(Mar 3, 2020 04:08 AM)Consulting Detective Wrote:  Hi guys. I'm messing around with file encryption in C. I wrote a small program that will take a file, process it through 3 encryption algorithms and creates a new file with the encrypted output.

My problem is that after the string in the buffer goes through the first algorithm, it is not giving the right output I want.

Output:

PHP Code


<?php 
Thequickbrownfoxjumpsoverthelazydog.   //buffer
a√L    //result of first algorithm
u√L
0╛g 


PHP Code


<?php 
#include<stdio.h>
#include<string.h>
#define XOR_KEY1 0x2B //nice
#define XOR_KEY2 0x45 //golden rule


int main(int argc, char *argv[]) {

 char buff[1024];
 char placeHolder;
 int len = strlen(buff);
 int x;

 FILE *sourceFile;
 FILE *destFile;
 sourceFile = fopen(argv[1], "r");
 destFile = fopen("encryptedFile.txt", "a");


 while(feof(sourceFile) == 0) {

 fgets(buff, sizeof(buff), sourceFile);

 puts(buff); //prints initial content of buffer

 for(x = 0; buff[x] != '\0'; x++, len--) { //1st obfuscation
 placeHolder = buff[len-1];
 buff[len-1] = buff[x];
 buff[x] = placeHolder;
 if(&buff[x] == &buff[len-1] || &buff[x+1] == &buff[len-1]) {
 break;
 }
 }

 puts(buff); //prints output of 1st

 for(x = 0; buff[x] != '\0'; x++) { //2nd obfuscation
 switch(buff[x]) {
 case 'a':
 buff[x] = 'u';
 break;
 case 'e':
 buff[x] = 'o';
 break;
 case 'o':
 buff[x] = 'e';
 break;
 case 'u':
 buff[x] = 'a';
 break;
 case 'A':
 buff[x] = 'U';
 break;
 case 'E':
 buff[x] = 'O';
 break;
 case 'O':
 buff[x] = 'E';
 break;
 case 'U':
 buff[x] = 'A';
 break;
 default:
 break;
 }
 }

 puts(buff); //prints output of 2nd

 for(x = 0; buff[x] != '\0'; x++) { //3rd obfuscation
 if(buff[x] == 'O') {
 continue;
 } 
 if((x % 2 == 0) && (x != 0)) {
 buff[x] = buff[x] ^ XOR_KEY1;
 continue;
 }
 buff[x] = buff[x] ^ XOR_KEY2;
 }

 puts(buff); //prints output of 3rd

 fprintf(destFile, "%s", buff);
 }

 fclose(sourceFile);
 fclose(destFile);

 return 0;

} 


P.S. sorry for the messy code, still learning.

(Mar 3, 2020 04:44 AM)Zexture Wrote:  You're getting the length of the string before reading it from the file and writing it into the buffer