Program licensing

Hello everyone,

I am trying to make a nice licensing method to use with my C-programs.
I have implemented a simple method like the following:
* KeyFile.cfg - contains the following
- ActivationKey
- Expiration Date

* Program contains
- ProgramUniqueKey

Now for input in the program I use the following:
* Input into program
- IP-address
- Expiration Date (from KeyFile.cfg)
- Activation Key (from KeyFile.cfg)
- ProgramUniqueKey

I use Crypt mechanism to crypt the input data and verify that against the Activation Key. Those have to be the same.

I am looking for a method of checking the date, to see if the key is still valid without entering an Expiration Date manually into the KeyFile.cfg

I have searched and searched for such a mechanism but have failed to find anything that comes even close.

Does anyone have any experience in this matter, or have some good reference sites where I can start from?

Any help is appreciated, also C++.

Thank you in advance,
Kind regards, Tom.

Well, you could implement it into the key itself somehow. However, you would probably want to have it encrypted in the key, not in plain text.

Off course I want to encrypt it into the key.
Otherwise the user could just change the key as that will most likely be clearly visible....Still I am uncertain how to perform that as I need to decrypt it somehow as well.....

Hmmm, now that is a nice idea, we are getting closer to perfection :-)

Hmmm, MD5....can I use MD5 out of the box?
What would I need for MD5, though I believe that for the uniqueness the crypt will do....

Another question......how can I use this stuff on Windows 2K / Xp?

I tried the wincrypt.h but that is quite different from the crypt mechanism.....

Thanks, Tom.

I thought its better to post my doubt in this thread rather than going for another...well,,,

U do one-way encryption or whatever to store the expiry date.
And what i understood is ultimately this expiry date will be compared with the system time..right!!!

what if the user everytime changes his system time. will the product never expires!!!!

Is there any method to solve this.

Please explain.

thanx.

Hmmm, I do not really need a check for that.....this since the software I develop highly depends on a steady flow of the system date.

But if you would need it somehow.....hmmm, Perhaps on windows you could put it in a registry file.....I would not see how you could easy develop any license that will disallow your user to change system date/time.

After all, all software is going to get cracked or keygenned anyway, but it is just just to put some level of key-enabling in it.

Hope that helps a bit.

Did anyone have any crypting info on how to compile this windows?