Re: Brute force question

From: Michiel Buddingh' (michiel@nospam.com)
Date: 03/10/03 

From: "Michiel Buddingh'" <michiel@nospam.com>
Date: Mon, 10 Mar 2003 22:27:13 +0000

On Mon, 10 Mar 2003 13:33:46 -0500, Jack Lloyd wrote:
> For image/audio, it's fairly likely it has a magic number at the
> beginning of the file (for example, JPEG files always start with 0xffd8,
> followed either by JFIF or Exif). Of course you will end up with a file
> matching this about 1/2^31 of the time, in which case you'll have to do
> something like decrypting the entire file and passing it to a JPEG decoder
> to see if it's valid JPEG data.

I wonder how effective an index of coincidence test would be in
distinguishing `meaningful' binary data from garbage. Instinctively, I'd
say it wouldn't be, as binary formats tend to have less redundancy than
written text. Then again, my instinct is wrong about statistics 90% of the
time. 

-- 
				-- michiel