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From Jörg Schmidt <joe...@j-m-schmidt.de>
Subject a very special question about the OOXML fileformat
Date Wed, 09 Apr 2014 21:42:12 GMT
Hello,

I hope the following is not OT, although it is not specifically a question about OO:

I save the same file in MS Excel 2010 (a) and LO 4.1.x (b) in OOXML format (*.xlsx). Now I
look at the file headers of (a) and (b) and find the first 10 bytes:

(a): 50  4B  03  04  14  00  06  00  08  00
(b): 50  4B  03  04  14  00  08  08  08  00 

Because they are zip files the first 4 bytes are 50 4B 03 04 and equal, as well the following
two bytes are equal. However, bytes 7 and 8 differ. OK, in principle i can look up what these
bytes encode:
https://users.cs.jmu.edu/buchhofp/forensics/formats/pkzip.html

My question is what values for these 2 bytes of the header are allowed at all so it still
corresponds to the ISO standard for OOXML.

In the ISO standard: 
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=51463

i could not find anything so far. 
There is only general talk of the zip format and I'm not sure whether that means that the
values after byte 4 can be differently, depending on the program that are used.


Greetings,
Jörg


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