Re: Using compression before encryption in device-mapper

[Bill Davidsen]

On Wed, 14 Apr 2004, Paulo Marques wrote:

> Guillaume Lacôte wrote:
> 
> >>>Oops ! I thought it was possible to guarantee with the Huffman encoding
> >>>(which is more basic than Lempev-Zif) that the compressed data use no
> >>>more than 1 bit for every byte (i.e. 12,5% more space).
> 
> WTF??
> 
> Zlib gives a maximum increase of 0.1%  + 12 bytes (from the zlib manual), which 
> for a 512 block will be a 2.4% guaranteed increase.
> 
> I think that zlib already does the "if this is bigger than original, just mark 
> the block type as uncompressed" algorithm internally, so the increase is minimal 
> in the worst case.

I kind of think that the compression, even negative, is wanted here to
assist in obfuscation.

-- 
bill davidsen <davidsen@xxxxxxx>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

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