xor encryption inopérante

**Rniamo** · 23/09/2008, 00h36

bonjour,

au cvours de mes ballades on line j'ai trouvé un challenge qui m'a intrigué :

XOR Encryption (which most people will tell you is not really encryption at all) is performed by taking a key and xoring each byte in a file with the each byte in the key. This is generally performed by moving through the key a character at a time, and repeating when the end is reached.

Take this file and xor it with the string secret (restart at s when you come to t).

Then exchange the following byte values in the file:

# 23 with 0
# 78 with 66
# 36 with 144

and the other way round!! i.e. 0 with 23

Save the result as a file and rename it to .jpg Open it in a picture viewer and the resulting message is your solution.

j'ai codé ça :

Code :

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#include <iostream>
#include <fstream>
 
int main() {
	std::ifstream f("data.bin",std::ios::binary);
	std::ofstream out("sortie.jpg",std::ios::binary);
	std::string key("secret");
				int i=0;
	if (f.is_open() && out.is_open()) {
		int y=0;
		unsigned char c=f.get() ^ key[y];
		while(f.eof()!=true) {
			(y == key.size())? y=0 :y++;
			switch(c) {
				case 0x0:   c=0x17;  break; // 0 <-> 23
				case 0x42:  c=0x4e;  break; // 66 <-> 78
				case 0x90:  c=0x24;  break; // 144 <-> 36
				case 0x17:  c=0x0;   break;
				case 0x4e:  c=0x42;  break;
				case 0x24:  c=0x90;  break;
				default:break;
			}
			out << c;
			c=f.get() ^ key[y];
		}
	}
 
	return 1;
}

Mais ça ne marche pas. où est le problème ?