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BlueOwls Nibble Compression Engine

Author: BlueOwl

Published in DCA#1 magazine

Author's comments


I made this engine for virusses which want to use some algorithm to make themselves or something else smaller (obviously), but i wanted the algorithm to be small too, because if it isn't it would have little use for virusses. In this case, I tried to make the decompressor as small as possible, and let the compressor do most of the work.

How it works

Every byte has 4 nibbles and these can be compressed. The compression is done by counting the number of nibbles in the entire data and change the nibble sizes accordingly. The most common of the four possible nibbles will be compressed, #2 will stay the same size and #3 & #4 will be expanded. This means that as long as the number #1s > the numbers #3+#4 compression occurs, otherwise the data will be expanded. The maximum reducement is 50%, and the maximum enlargement is 112,5%.



bnce.zip2777BNCEOct 2004MD5 sum 35b5ab199e9acdeff93a8df08b951040

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