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List:       hpux-devtools
Subject:    Re: HPUX-DEVTOOLS: Implementing a Licence String
From:       "Richard J. Rauenzahn" <rrauenza () cup ! hp ! com>
Date:       2001-05-18 16:41:22
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> I've been asked to embed a licence string into our HP-UX 11.0 C application.
> The objective is to allow prospective customers to install the software on a
> trial basis but for it to stop working after 30 days or at a nominated time.
> We would be able to extend the licence by sending the customer a further
> licence string.
> 
> I guess it must have been done before.  References or tips welcome.

If you don't want to use a 3rd party product (like FLEXlm), then you
might start by using 'uname -i' to identify the machine -- although some
people will use the primary lan card's MAC address.  Before I go on,
I'll highly suggest you check out the security newsgroups -- maybe
comp.security.misc or comp.security.unix.

You could encode the identifier and an expiration date into a license
key and then use public/private encryption -- or perhaps a hash/digest
of the key.  

A simple example would be putting the id/expiration date in plaintext
but signing the text with a private key.  Your app would then have the
public key to check the license's authenticity.  I'm speaking way out of
my area of expertise here, so I still recommend fishing around in the
security newsgroups.

Rich
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