I have a question relating to protecting the code I've developed for a few
excel spreadsheets.

I've recently been sent a spreadsheet that I've found requires a licence
key to unlock further functionality. As far as I can tell, the spreadsheet
is fully functional but there is a time limit on the use of the it
unlicenced.

I presume this would require some form of encryption. Can anyone point me
in the right direction so that I can implement something similar in my
spreadsheets. And where would the key be recorded? A flat file would be
easy prey to a hacker so I presume the use of xlVeryHidden here.

Any help would be greatly appreciated.

Cheers,

Geo

Geo

even if it is an xlVeryHidden sheet, this is not secure. You could write a
routine in a few seconds to make the sheet(s) visible. Excel is not
designed to be "secure".

Regards

Trevor


"Geo Harris" wrote in message
. 110.130...
I have a question relating to protecting the code I've developed for a few
excel spreadsheets.

I've recently been sent a spreadsheet that I've found requires a licence
key to unlock further functionality. As far as I can tell, the spreadsheet
is fully functional but there is a time limit on the use of the it
unlicenced.

I presume this would require some form of encryption. Can anyone point me
in the right direction so that I can implement something similar in my
spreadsheets. And where would the key be recorded? A flat file would be
easy prey to a hacker so I presume the use of xlVeryHidden here.

Any help would be greatly appreciated.

Cheers,

Geo

You could password protect the VBA code - but there is software around that will crack this so Excel is never 100% secure
I recently wrote an algorythm - where the password required by the user is actually calculated in VBA - so the user has to ask for a password from the administrator that would then be valid for an hour or so. This turned out to be quite useful as the administrator was then in total control of all access to the workbook. This can still be cracked though, but the code would be tough to find and follow through. Software to crack VBA is less available than software to crack workbooks/worksheets

If you want to know how the author of your workbook built the protection, e-mail me off-list and I'll give you an address you can send the workbook to where I'll open it up and see whats going on.