This topic comes up repeatedly in sci.crypt.  Google for it.
The general consensus is that it is a waste of time.
A determined hacker will compromise any copy protection
system and once the system is compromised an infinite
number of copies can be made. That is a single compromise
is fatal to the system.

Microsoft has spent a ton of time and money on the issue and the best
they can do is produce updates that "break" compromised copies that
download them.  Unless you are planning on spending more time and
money than microsoft, make it easy on legitimate users and hope your
software is worth pirating.

Leslie 'Mack' McBride
remove text between _ marks to respond via e-mail

Hello Paul,

Im a firm believer of buy vs build in this area. Take a look at xheo licensing:
http://www.dotnetlicensing.com. This is (IMO) the best licensing component
out there right now.

--
Matt Berther
http://www.mattberther.com

Paul,

"Paul Aspinall" <paul@aspy.co.uk> schrieb:

.NET's licensing mechanisms:

.NET Framework Developer's Guide -- Licensing Components and Controls
<URL:http://msdn.microsoft.com/library/en-us/cpguide/html/cpconlicensingcomponentscon
trols.asp>

.NET Licensing
<URL:http://windowsforms.net/articles/Licensing.aspx>

Commercial components:

XHEO|Licensing
<URL:http://www.xheo.com/products/enterprise/licensing/>

I regularly use a license key method that I've found to be very safe. It
involves the construction of a long string of data such as the computer
name, user name and other metrics that are unique to the machine the product
is to be installed. This long string is used to generate a hash key that is
unique for every installation. In most instances I use a web-service to do
the key generation so that is under the control of my server.

I created a licensing component that uses this hash key to grant or deny
licenses based upon runtime / design time use and I also do horrible stuff
like check for the presence of different sorts of debugger running on the
machine. This licensing component is heavily obfuscated with an obfuscator
that crashes the IL disassemblers and it's guts are also encrypted wherever
possible.

I feel that I can explain this because the heart of the system depends upon
so many factors that go together to create a string of information which
averages about 1000 characters. Hash key cracking systems such as lookup
tables are unreliable past 15 or 20 characters so my strings with all the
weird information I collect are, I think, quite safe.

IMO If anyone has the energy to crack such a variable system as one that is
different for each and every installation, even if it's installed twice on
the same machine, then they are the very low percentage of people who will
be deterred by nothing. I know that a single crack would take an
inordinately long time and the key is so simple to change that a trivial
update on my part will make the hackers have to go through the whole reverse
engineering process again.

Infralution offers a reasonable priced encrypted licensing solution.
You can download an evaluation version at:

www.infralution.com/licensing.html

As several posters have noted, nothing that you can do will stop a
really determined hacker from cracking your software in one way or
another.  However, a licensing system offers protection similar to
locking the doors of your house - it won't stop the determined thief -
but it will stop the casual passer by.  The level of protection you put
in place depends on the value of what you are protecting and the
likliehood of people wanting to steal it.

Regards
Grant Frisken
Infralution