Adding Sheet Invalidates Digital Signature

[Guest]

(see various posts on this subject in this group - all without any fix)

Simply put, any macro in a signed excel project that adds or deletes a sheet
will invalidate the digital signature causing macros to be disabled next time
the workbook is loaded. Thsi seems to apply to Office XP and 2003 at least.

It appears that the digital signature includes not only the VBA code
modules, classes, etc. but also the sheets collection! This is particularly
annoying as the sheets I'm adding (copy from existing hidden 'template'
sheet) don't contain any code and this bug/feature isn't documented anywhere
I could find.
Obviously, changing the contents of a sheet is possible without invalidating
the signature. How is adding a sheet any different? Maybe the hashing
algorithm assumes that each sheet always has a code segment and always
includes it - even though it is empty? Is there some way I can ensure that my
template sheet is code-free and therefore always excluded from the hashing?
I've tried a workbook cleaning utility but that didn't help.

Any suggestions (that don't involve COM or add-ins) or even a patch to Excel
from Microsoft would be very welcome.

 

[Guest]

Simon:

I believe that it has to do with the fact that every sheet has a "module"
and can have code added to it. Do you absolutely need to add an undefinite
number of sheets? Because if there's a maximum of sheets you will be creating
you could just hide them before you sign your macros. Then instead of
creating new sheets, you will unhide them.

Another way of doing it could be to design your macros to work by creating
new workbooks. That way you won't need to modify the original.

That's all my advice Simon, I hope that helps.

Sincerely,
G.Morales

 

[Stuart]

Would it work if the workbook containing the code was a template, and the
user simply opened a copy?
Don't know......just a thought.

Regards.

 

[Guest]

Hi Simon,

The only approach I can see that can fit your described requirements at this
time is to create a separate control file (Signed) to open the working file
(Not Signed). The control file can include a workbook open event to open
the working file - taking advantage of the default msoAutomationSecurityLow.

I agree this is only a work around to a real problem.

Best Regards,
Walt Weber