Signing MS-Excel spread sheets

[Berend Tober]

Kimmo Surakka wrote:

> Berend Tober wrote:
>
>> Indeed, and I even included in my original post "(Aside from the  
>> obvious -- "Stop using MS-Excel!" -- because that is a failure I  
>> cannot control...)".  Kids these days....
>>
>> Anyway, I've looked at WinPT and GPGee and one other GUI wrapper  
>> around gnupg, but they all of course are victims of this MS Excel  
>> "feature", and furthermore none of them satisfy my other need to be  
>> able to support multiple persons signing any given document, either  
>> (cf. other mailing list message thread "Multiple signatures on a  
>> single file").
>
> 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.

The comand script I'm refining seems to do all that I need, even if it 
has some rough edges:

gpg --sign.cmd:

@echo off
if .%1. == .. exit

attrib +r %1
gpg  --detach-sign --armor --comment "Signature of %USERNAME%" 
--local-user %USERNAME% -o - %1>>%1.asc



along with

gpg --verify.cmd:

@echo off
gpg --verify %1
echo.
pause


to list the co-signators. Lastly, I make short cuts in the Windows "Send 
To" folder, putting these two features in the Explorer context menu. 
Seems to work o.k.

-- BMT