Protecting Spreadsheet

[Ashman]

Hi all,

I have developed a spreadsheet that I am planning on selling. I am offering
a free trial of my spreadsheet, and after 30 days, it lock the user out.
This does not stop the user from downloading another version.

Is there anything in excel or some coding that will remember if someone has
downloaded the trial version before?

Any help would be much appreciated.

Thanks

Jason

 

[Vasant Nanavati]

Nothing that cannot be circumvented. Also, how do you plan on "locking the
user out?"

 

[Dave Peterson]

You might be able to put something into the windows registry and check it when
you open the workbook.

But if you can put it there, then anyone can clean it up. So it's not
foolproof.

Look in VBA's help for GetSetting and SaveSetting for examples.

But this would also depend on having your project protected--and that protection
can be bypassed pretty quickly.

 

[dominicb]

Good evening Jason

You could use the SaveSetting and the GetSetting instructions to writ
a key to the registry - this could be used to highlight whether a P
has used this particular software before. Be aware, however that Exce
applications can be "broken", VBA project passwords can be remove
fairly easily by those in the know - and if someone knows how to remov
a VBA password, they'll know enough about VBA to trace what you've don
and remove it.

HTH

Dominic

 

[William Benson]

I am more optimistic that controlling the distribution / the integrity of
the code would be more a business software developers concern, than people
not paying the licensing fee. And even where we've come to expect no honor
in the population at large - downloaded music - I just read tonight that
iTunes downloads has eclipsed P2P music downloads.

http://news.yahoo.com/news?tmpl=story&cid=620&ncid=620&e=3&u=/nf/20050608/bs_nf/36124

Would any of the developers in this forum care to share their thoughts for
naive souls like myself to learn from?

Thanks...

 

[Vasant Nanavati]

I'm not a developer, but have been around Excel NGs for many years. And I
can tell you that most "real" Excel developers rely primarily on the honor
of the general public.

There is no good way to protect any Excel-based program from unethical
users. You have to deem it a cost of doing business.

Additionally, I find that those who post questions about "protecting" their
programs have a highly inflated view of the value of the same.

Just my $0.02.

--

Vasant

I am more optimistic that controlling the distribution / the integrity of
the code would be more a business software developers concern, than people
not paying the licensing fee. And even where we've come to expect no honor
in the population at large - downloaded music - I just read tonight that
iTunes downloads has eclipsed P2P music downloads.

http://news.yahoo.com/news?tmpl=story&cid=620&ncid=620&e=3&u=/nf/20050608/bs_nf/36124

Would any of the developers in this forum care to share their thoughts for
naive souls like myself to learn from?

Thanks...

 

[John.Greenan]

If you mean just a simple spreadsheet - with no code - then there's nothing
you can do. Any VBA code can be hacked in minutes - just google "excel
password protection" for tools to do this. The safer way to do this is write
the code as VB and compile into a COM add-in for excel. Then have this look
at the registry for a hidden value. But, it's trivial to see what is being
written and read from the registry (regspy is one such tool) so you cannot
really do this.

For what it's worth, I think you are better off compiling the code with a
drop dead date. Then the "bad" user will have to change their system clock
to get the code to work.

Generally, this does not work too well, except in the case where the user
supplies parameters that you compile into the code, but that's very very
messy.

 

[Dave Peterson]

I agree with Vasant.

Protection will keep the non-curious honest users out. But even the honest
curious may be overwhelmed by the challenge <bg>.