On Fri, 6 Oct 2000, Tom Vogt wrote:
Lossy compression.
balance snipped, we need lossless compression, eh?
nope we don't. remember that everyone said that .jpeg couldn't be used for stego for that same reason? then the first .jpeg-stego tools arrived.
The only problem with lossy compression is that it severely limits the capacity of the covert channel. On the other hand, embedding a maximum amount of data into a data stream and losslessly coding the result will certainly show in the compression ratio. Some recent work in audio watermarking has achieved speeds of a couple of hundreds of bits per second. Of course most of those do not get through mp3 but the good thing is that these methods are for all practical purposes inaudible. Built for realtime use with e.g. shoutcast such methods should be capacious enough even after error correction. There's certain irony in using copyright protection research this way, as well... Sampo Syreeni <decoy@iki.fi>, aka decoy, student/math/Helsinki university