So you have a  programming problem -- and there are any number of ways to 
do what you want. When I say "program" here I'm really referring to the 
specific functions which will create the key and interpret the key.

1. What do you want out of the program? What results? What exactly do you 
expect the key recognition algorithm to do? Will different features be enabled?

2. What language are you writing in?

3. Where are you going to generate the key?

4. Where will you store it? Where will the user be expected to store it?

5. What will the program do if the key can't be found?

And there are probably more questions than that.

Common approaches are to take the name the user registers as, and pick up a 
system date or in your case the date of purchase, and create a key from 
that. (Purchase date is a bit tough, suppose they don't get around to 
installing it?) This can be stored in Windows registry or, more simply, in 
some license file.

As for the encryption/encoding part, you can rely on built-in functions in 
the language you are using, or devise your own. The key can be multi-part.

In other words, this is your oyster - Miles Thompson

PS Actually, don't you want the opposite? An algorithm that lets the user 
work with the program for 30 days from installation, then prompts for 
registration as the period ends, and then just stops working altogether? Or 
at least forces a reinstall?

PPS Go to one of the cracker sites and see how they reverse engineer 
various protection schemes, then do some reverse engineering of your own.

PPPS Try opening up a conversation with the owners of UltraEdit or 
Time&Chaos and see if they can give you some direction. This isn't the sort 
of thing people are willing to discuss, as you are talking about locks on 
the family jewels.

PPPPS Finally, recognize you are keeping honest people honest, there will 
always be those who will try and crack whatever protection scheme you have.

At 02:49 AM 8/6/01 -0700, Richard Kurth wrote:
>I am getting ready to wright a registration key for my program. This
>is so I can distribute the program say for 30 days and at the end of
>that 30 days the user will have to register the program or it will not
>run. This program will be encrypted So no they can not mess with the
>code. I would like it to be based on there domain name and also date
>of purchase. I am not sure how to go about this and I would really like some
>pointers in what direction I should go to do this. Sort of an outline
>on what I need to do to the program itself and how to generate a
>different key for each customer.
>Best regards,
>  Richard
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