HCM BLACK PAPER
- From: biject <biject.bwts@xxxxxxxxx>
- Date: Thu, 28 Aug 2008 08:23:44 -0700 (PDT)
Mr E as he calls himself breaks a file up into 3 files plays
compression gains/ And thinks that if he
remakes a sigle file out of it that it will be smaller than the
original file. He makes the false assumption
that as original file get longer that the overhead of combining the
3 files is somehow fixed. This is a
big mistake.
Take 3 bit files. Think of them as packed in a single string made up
of zero or more bits
of data followed by and EOS sybmol. Now convert to a hybred structure
where the 3 files concatenated togerther. Notice its a single bit
file but has 2 embedded
EOS in it not counting the normal EOS at end of string.
Suppose you wish to replace thow middle 2 EOS and the bit with a
single bit pattern.
You need the new bit pattern to acount for the cuttent binary bits
plus those 2 EOS
if you look at the number of cominations based on moving the 2
emdedded EOS you
get ( M +2 ) ! / ( (M!) * 2 ) thats the combinations that the extra
2 symbol give
compared to the single sring of M bits you get form concatinating the
3 files.
Example if suppuse M is 6 bits which means
the bits in the 3 strings total 6 bits
How many bits iin the single file when combined
to a single file. Well there are (8!)/((6!) *2) or
28 in binary 4 something meaning it would cost
about 4 bits. of voer head to combine the 3 file
It also means the a srarting string file of 10 bits
could be mapped with ease to 3 file total bits is
6
As M grows so does the number of bits needed to
combine the file.
There is not free lunch in compression
David A. Scott
--
My Crypto code
http://bijective.dogma.net/crypto/scott19u.zip
http://www.jim.com/jamesd/Kong/scott19u.zip old version
My Compression code http://bijective.dogma.net/
**TO EMAIL ME drop the roman "five" **
Disclaimer:I am in no way responsible for any of the statements
made in the above text. For all I know I might be drugged.
As a famous person once said "any cryptograhic
system is only as strong as its weakest link"
.
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