Sorry if these questions have been answered in posts I recently deleted, but... 1) Instead of modifying Huffman coding, isn't it more sensible to just use arithmetic coding, which is more efficient anyway, and doesn't use fixed bit patterns? 2) I would assume there's a branch of cryptography devoted to studying the protections or lack thereof, afforded by compression schemes, both by themselves and in addition to other types of cryptography. I would guess that Huffman and LZ-family codes have been studied a lot...right?? But also more general studies of the weakness of (even secret) compression algorithms as crypto methods? I mean, compression methods would tend to use methods (like table lookup) that simpler cyphers have used for a long time, only without having been designed with crypto expertise...right?? 3) Does anyone know of an easy-to-get-sources, easy-to-use arithmetic coding compression program? quote me -fnerd
3) Does anyone know of an easy-to-get-sources, easy-to-use arithmetic coding compression program?
I have a book titled "Data Compression" or something like that, which explains Huffman and Huffman-type coding, arithmetic coding, dictionary compressers (sliding window LZ* types), and JPEG compression. The book comes with source code, so if anybody else has it and has a scanner... As I recall, arithmetic compression works well, but is really cpu intensive, even with a math-coprocessor. Plus, you need to have a rough idea of the statistical breakdown of the plaintext for arithmetic compression to work as well as it can. The Zimpel-Lev type sliding window compressors are popular because they work well on most inputs, with little or no pre-computation or statistics. Isn't Phil Karn on this list? I'm sure he can tell you everything you want to know about compression :-) /-----------------------------------\ | Karl L. Barrus | | elee9sf@menudo.uh.edu | <- preferred address | barrus@tree.egr.uh.edu (NeXTMail) | \-----------------------------------/
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