Signing MS-Excel spread sheets

[Samuel ]slund]

On Mon, Sep 05, 2005 at 08:07:13AM -0400, Berend Tober wrote:
> Kimmo Surakka wrote:
> 
> >Just my two cents worth: isn't it true that most Windows zippers can  
> >open a file "from inside a zip archive", i.e. uncompress it  
> >transparently to a temp directory and open from there? One easy-to- 
> >use solution could therefore be to store the Excel file inside a zip  
> >archive, and then sign that archive? When the second person opens the  
> >spreadsheet, all the changes Excel wants to do are done to the  
> >temporary copy -- not the actual spreadsheet itself.
> 
> The sounds like it would work, but I don't like the idea of imposing the 
> extra layer of the separate zip application like this between the 
> document and the signing step -- although it could be the approach we 
> have to take if we bring this to the next level and scan the supporting 
> documents (i.e., receipts) to jpeg files for inclusion along with the 
> spread sheet -- which would be pretty cool. However, I still have the 
> issue being discussed in a separate-but-related thread concerning 
> co-signatures.

Another option with zip-archives, if you put the signed .xls and the
signatures in the zip you should get the nonmodifiable effect and keep
the signatures "attached" to the file.

With luck there is some way to ask the zip program to execute your
sctrip...

//Samuel