Most times it is done with a public/private key pair. The server signs a
license (full, or trial) and the license has an expire date and license
type - among other fields you want to track. This could be just a simple
xml file in plain text. The signature could only be signed with your
private key at your server site. Then distro the license files as needed
(purchased, etc). If the user does not have a valid license file, your
program stays in eval mode (for example.) So absence or presents of a
license file is the controlling factor, not some reg key that you can't
really hide anyway. The program verifies the license and signature using
the public key. It gets a bit more complex as now this license will work
for anyone. So you also want to factor in a machine hash so that means they
need to send you a machine hash (that your program calculates) and that is
stored in the license. The program also verifies the machine hash in
license against a new machine hash that calculated at each startup to see if
they match. Simple in the abstract, but the devil is in all those details.
That is why I pointed you to the MS code that already does all this for you.
--
William Stacey [MVP]
"Mike9900" <Mi******@discussions.microsoft.com> wrote in message
news:48**********************************@microsof t.com...
Sounds nice, but does anyone knows of any algorithm I can use for this
purpose?
--
Mike
"WRH" wrote:
Hello
Perhaps writing encrypted values in the registry not during
installation but upon first startup and in two locations, one not
associated with the app. I believe the only way to delete it would
be a registry edit of both locations. I realize that the keys would
be left over if the app is uninstalled and thus the app would not
be a good registry citizen but its hard to come up with
reasonably secure means.
"Mike9900" <Mi******@discussions.microsoft.com> wrote in message
news:B2**********************************@microsof t.com... > Hello,
>
> We want to add a secret code which is the expiration date and the
> number
> of
> uses of the trial software in storage. Saving this code in the Windows
> Registry is not a good choice, because the user may not have access
> right.
> Also adding it to IsolatedStorage is for one user and is not for all
> the
> users. Eventhough I thought IsolatedStorage could help on this.
>
> I am wondering how and where we could add the expiration date and
> number
> in
> a safe place, so it will be hard for the user to find and delete that
> code.
> Is there any other idea on how to manage the trail software expiration,
> so
> it
> will expire at the specified date or the number of uses?
>
> Regards,
> --
> Mike
>