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Time Limited Use

By wajacob ·
I program in VB6 and would like to hear how one may allow people to install and use a program for a limited time. For instance if you purchased a one year licence to use a product.

Any assistance would be appreciated.

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Your best bet to find techniques

by Tony Hopkinson In reply to Time Limited Use

is to search for people who teach you how to crack them. It can be something as simple as a filedate or a registry entry (not an obvious one). To a special compilation (Build the expiry into the executable).
All of these are quite crackable if you want to go to to the trouble, which in itself is a backhanded complement.
You might be better off with a limited feature set idea.
If it lends itself well, a nice way is to to do it over the web with a sign on and check on execution. OK someone could crack the file where you hold the data on your server/isp, but that at least is much harder than regedit or using a hex editor on the exe.
Personally I'd put more effort into having them want to pay you rather than having to pay you.

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check out astalavista.box.sk

by Why Me Worry? In reply to Your best bet to find tec ...

they have serials and cracks for pretty much every piece of software imaginable

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Thats because

by Tony Hopkinson In reply to check out astalavista.box ...

a load of greedy b'stards with low quality products can't be bothered to spend anymore effort in securing it than they could in writing it in the first place.
The only reason I suggested looking up how to crack, is because one article I saw the guy explained the mechanisms that caused him the most problems. Not interested in cracking anything myself, but I was interested in simplish and cost effective measures to implement software protection.

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This is what I do

by jmiller In reply to Thats because

I use the following method to secure apps.

1. Add some encryption code to your app. There are lots of examples available for you to work from.

2. Create an encrypted file that contains an expiration date and the last date used. Update the last date used each time they run the app, but only if it is later then the previous "last date".
This keeps them from setting their clock back.

3. If you want to limit the usage to one machine, you can add the harddrive serial number as well. This means that you would need to provide a custom lock file for each user. You should also know that machines from the same vendor may have duplicate harddrive serial numbers.

There are still ways to get around this, but it is close to having a hardware dongle.

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by RandaraC In reply to check out astalavista.box ...

Save your ending date into a memory variable(*.mem in VFP, VB. Save this, with any name and extension, in a folder full of files, let's say C:\windows\system32.
Every time the app is run check the computer date against this one. If he set his clock back he will get files with a wrong date, invoices, etc. This check can be done in any screen of the app.

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Easy to get round

by Tony Hopkinson In reply to

and bad practice.
Files changed since will find that in 'seconds', and crackers always look for that one and a registry compare.
Application writers who just wodge stuff into my system folders are damned annoying as well, That's not what they are for, they are for OS stuff not application.

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You can purchase a DLL product that can do just that.

by craigestano In reply to Time Limited Use

I purchased a product from VBxtras.net it is by a company VBWare called LicenseDLL for $58.00. It allows you to control the evaluation of a VB6 program by time or # of runs. But with a little imagination you should license a program for (say) one year. You can write these things yourself but for $58 it was a great buy. There are other similar products.

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Thought about a dongle?

by blarman In reply to Time Limited Use

A lot of programs have time-bombs written into them that force you to buy the software after X days to continue using it. The company I work for uses another method: a USB dongle. The software time-bomb is still there, but it looks for a dongle after time is up. If the dongle is present, the software runs.

For more, check out http://www.smartdongle.com/

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