On Wed, 18 Jul 2001, David Honig wrote:
1. encrypted data is indisttinguishable from uniformly distributed noise
Yes, but which natural data sources have that signature?
2. LSBs in digitizations of analog signals are noise
Not uniformly distributed noise, unfortunately. Perhaps somebody should put hardware entropy generators mixing white noise into multimedia steam LSBs. People should definitely package stegano decoys into Open Source streaming multimedia warez.
3. ignoring the nuance of different LSB distributions, how can you distinguish a stego'd from unaltered file?
By running a simple statistical test (most packages don't even pad, so you can vgrep for it). There is some pretty bulletproof stego out there, but 90% of it wouldn't stand a trace of scrutiny. Of course it limits the processivity of the screening.
Stego by itself is much less interesting than stego'd encrypted data (with idenntifying headers stripped of course)
The point of stego is not leaking the information that you're sending other information.
That spam, mp3, or image could be merely a transport for more privledged info. Posting /reading to a public newsgroup solves traffic-analysis issues too.
-- Eugen* Leitl <a href="http://www.lrz.de/~ui22204/">leitl</a> ______________________________________________________________ ICBMTO : N48 10'07'' E011 33'53'' http://www.lrz.de/~ui22204 57F9CFD3: ED90 0433 EB74 E4A9 537F CFF5 86E7 629B 57F9 CFD3