On 20 September 2016 at 12:18, Alan Young <ayo...@teleport.com> wrote:

> This is correct. 7zip is not the problem. The problem is the end user's
> unzip application. The zip specification has been extended over time to
> support additional compression methods. See
> https://support.pkware.com/display/PKZIP/APPNOTE and
> https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT.  Section
> 4.4.3.2 has a quick summary of the feature versions. The current PKzip
> program will unzip the doc file created by 7zip.

This would all be fine if the file in question was a ZIP file.
According to my reading of even the latest version of the APPNOTE.TXT
file, IBM's file does not meet the specs for a ZIP file. In
particular, a required signature element is missing. Whether or not a
particular commercial product from PKWARE will decode this file misses
the point. It's not a question of new compression types; the entire
file wrapper is plain wrong.

Tony H.

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