Ian thanks for your detailed explanation for using
activation code. I will experiment it and if any
problem I let you know.

-Talon

--- Ian Bambury - JASWW <ibambury@j...> wrote:
> 
> Sorry Talon, I didn't see your reply - I'd been off
> for a week around then
> and I expect most things got set to 'read' without
> being read.
> 
> What I have done in the past for commercially
> sensitive software distributed
> only around our own offices (we have 160 in 80
> countries) might be a tad
> over the top for your stuff, but you can water it
> down...
> 
> I concatenate our product code, their hard disk
> serial number and create a
> checksum (say 1*1st digit + 2*2nd digit etc) and
> take the last 4 characters
> in hex e.g.
> 
> A621-1A23-7904-1234
> 
> I then xor them with another 4-digit hex number,
> then jumble the characters
> and get them to send me that string.
> 
> When I get it, I simply reverse the sequence and
> check the checksum
> 
> I now know the product code and their hard disk
> serial number
> 
> I then send them (similarly scrambled) the hard disk
> serial number, a start
> date, an end date, and a checksum. They enter it,
> the program saves it to
> the registry. Every time the program runs, it
> unscrambles it, checks the
> checksum, checks the hard disk serial, and checks
> the dates.
> 
> If the dates are invalid, I write to an obscure
> registry location and check
> for this every time.
> 
> Also, if you want to secure your program against
> hackers, you will need to
> check in various places, not just one. Also, for
> some checks, add a
> randomise function so it only checks once in a
> hundred tries (so stepping
> through the code to find the check is difficult),
> add checks such as
> 
> x=now
> for y=1 to 20:y=y:next
> if datediff("s",x,now)=0 then do_check
> 
> so if someone is stepping through the code, the
> check won't happen
> 
> also add checks to check the checks (!) i.e. call
> the check subroutines with
> known-invalid codes to se if they come back
> validated as okay - if they do,
> someone's modified the code.
> 
> It all depends how secure you want to be, how
> paranoid you are, how much
> time and money you are prepared to spend on it, and
> how much you think your
> product is worth.
> 
> HTH,
> 
> Ian
> 
> 


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