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best method to implement a 14 day demo version of a for resale program


We have developed a new VB based software program intended for resale and have reach the point of implementing some sort of 14 day demo functionality into it.  

Are there any suggestions regarding how we should determine whether the program's demo 14 days have passed.  A text file or registry key seem too easy to bypass and figure out if someone wants to compare the results of a system snapshot before and after install.  Likewise having the 14 days being based on the system clock, could be bypassed with the reversal of the clock's date.

How should we include demo functionality into the program?  How would those that have developed applications for resale done this?  What would your expert suggestions be?

Thank you for you help.

1 Solution
you have a few options
1. registry/file/something like that. as you said it's pretty easy to bypass
2. use PPP which will allow you to do it (but you will have to buy it) http://www.softwarekey.com/. this requires coding of the copy protection but it's very powerfull and easy
3. i think install shield has something like an envelope they put on your exe to time limit it.

i'd go with #2 since it gives you the most control of your software

Here is a free ActiveX control that may help you:



You can write a binary file and encode the date inside it in a way that you would be the only ones which can read it.

Let's say:
  (m) incidental characters and then an integer marking the Day
  (n) incidental characters and then an integer marking the Month

The file should be there at the beginning marked with 0's for each parameter (Day, Month, Year...)

The application would not run if this file is missing or been changed.

Notice that the bin file should be very big (say 0.5M) so it would be hard to crack it.
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I like ophirg's idea, but you should make sure that you write the file nested somewhere with hidden properties and that the uninstall program doesn't remove it and the install program won't overwrite it, otherwise a new install would work right around it.  I would suggest writing several hashes to the registry in addition to this file.  It is also a good idea to include the machine's MAC address if it has one to make sure an updated trial file from one machine won't work on another machine.


keeplivingAuthor Commented:
These options all use the same ideas that I mentioned in my question and said I did not want to use.  Sorry guys but I am going to let this question time out.

If you don't agree, please post and we can solve it.
Éric MoreauSenior .Net ConsultantCommented:
Don't let it time out. Ask the Community support (http://www.experts-exchange.com/Community_Support/) to PAQ it.
keeplivingAuthor Commented:
Oh cool, thanks for the suggestion Emoreau.
PAQ'd and 126 points refunded


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