At 07:46 PM 3/1/96 -0500, Mutant Rob <wlkngowl@unix.asb.com> wrote:

I'm wondering if anyone has done any work on schemes to lower the entropy of a given stream. Why? Save you've got message M encrypted with a good cipher, but you're worried that it can be detected because even with stego, the entropy is a lot higher than normal 'random' data flowing through a network.

Peter Wayner's work on Mimic Functions does just this sort of thing. You can describe a grammar, feed it random bits, and generate output that has the right statistics and can be reversed to get the original bits. His paper was on cs.cornell.edu a few years ago; don't know where to find it now. AltaVista yields a reference to the paper in Cryptologia, and the Cyphernomicon has the following: - "They encode a secret message inside a harmless looking ASCII text file. This is one of the very few times the UNIX tools "lex" and "yacc" have been used in cryptography, as far as I know. Peter Wayner, "Mimic Functions", CRYPTOLOGIA Volume 16, Number 3, pp. 193-214, July 1992.[Michael Johnson, sci.crypt, 1994-09-05] (When I read the Cryptologia reference on my browser, I don't get the ligature in the middle of "Huffman coding"; YMMV. :-)