Re: Licensing an EXCEL file
From: JE McGimpsey (jemcgimpsey_at_mvps.org)
Date: 03/05/04
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Date: Fri, 05 Mar 2004 10:18:10 -0700
password protection is useless. See
http://www.mcgimpsey.com/excel/removepwords.html
If you're not putting your functions in a compiled add-in, your formulas
will be visible to anyone with enough smarts to find these newsgroups.
Of course, going the COM add-in route eliminates sales to XL97/Mac
users, but that may be acceptable.
Expiration dates are as vulnerable as the code - generally a hidden file
is used to store date information so that the user can't just set the
machine's clock back. The date can be encrypted within a block of random
data to make it less obvious which data contains the date. Of course,
knowing that, it's not too hard to find hidden files and hack them, but
most business users won't be able to/interested in doing that. To be
commercially acceptable, you'll probably need to include some code
within your add-in for updating the license via a new license code.
In article <jo-dnTThMo0yL9XdRVn-jA@adelphia.com>,
"Grace" <Whooshbopbang4@adelphia.net> wrote:
> My boss wants to market an analysis file I have. He wants to license it to
> users on a per year basis. What will be ciritical is that no one can see
> the eqautions and that, somehow, it will expire in a year.
>
> Is password protection good enough that no one, short of a really
> accomplished hacker can break it? Also, can someone tell me how to best
> install an expiration date, one that can't be beaten easily?
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