[libvoikko] Zip specification

[Harri Pitkänen]

On Friday 24 September 2010, Sjur Moshagen wrote:
> Den 20. sep. 2010 kl. 21.13 skrev Harri Pitkänen:
> > - ZIP format has lots of options for compression, encryption etc. We
> > should figure out which ones are actually useful and allow only a
> > minimal subset of those features that meets these requirements to be
> > used. This would make it easier to produce a compatible implementation.
> > I'm not sure if all compression methods that have been used within ZIP
> > archives are free of patent issues. I can study this further and propose
> > something.
> 
> That would be excellent.

I'd suggest the following limitation to the format:

"The ZIP file must not be encrypted and it must be compatible with to ZIP 
format version 2.0 as defined by PKWare application note 6.2.0: 
http://www.pkware.com/support/application-note-archives"

I believe that ZIP files produced with commonly used tools will conform to 
this limitation. You can check the file by using the "file" command on Linux. 
If it says "Zip archive data, at least v2.0 to extract" then all should be OK 
unless you used encryption. But using the encryption algorithm of this ZIP 
version makes no sense since it is so trivial to break that it would provide 
no real protection whatsoever.

Harri