File Encrytor

[heljy]

Hey guys,

Got a quick question.

I am planning on writing a very very simple encryt/decrypt program just for the sake of it.

Now I understand that the simplest way is just to XOR the file with a key

EnC = file ^ key

DeC = Enc ^ key

Thats the baisc idea.

But how do I actually implement it??

So I read in a line from the file, using say fgets()?

Example Pesudo Code:

open file;
get key from user;

while(not end of file) {

msg = fgets(from file);
msg = msg ^ key;
fputs(to file, msg);

}

close file

So is that how I can do it?


Thanks!

[Shiro]

Don't know if it works but strings, but you can give it a try.

A different possiblity is reading a single byte, XOR the byte with a byte from the key and write the resulting byte to a crypt-file.

[heljy]

So the key would be a single byte as well??

I will try that out, thanks

[Shiro]

No, the key can be many bits. The key can even be as long as the source. What I meant was that the key is a bitstring, an array of bytes.

If you're key is 3 bytes, then you could use it like

dest [0] = source [0] ^ key [0];
dest [1] = source [1] ^ key [1];
dest [2] = source [2] ^ key [2];
dest [3] = source [3] ^ key [0];
dest [4] = source [4] ^ key [1];
dest [5] = source [5] ^ key [2];

Ofcourse in practice the key is much longer and you would use loops.

[heljy]

hmm...that sounds right

Thanks!