Copy protection tool to limit number of units

Question

I have written a winform application to manage a certain type of project. I want to charge my users on a per project basis, e.g. they purchase a base version of my app to manage 3 projects for 300$ and can buy extensions for 100$ per project.

Do you know of any good tools that support this type of licensing?

Currently the project counter is buried in the database, but I am looking for something more reliable.

Answer 1

For starters, you could store a hashed up version of the number of licenses as a check - it can be a hash, which is very difficult to reverse - then you can compare the "project licenses" field against the hashed field to ensure it hasn't been tampered.

You could then supply a new hash as the license key for more users, so it updates both the number of projects field and the hash. Use their "registered company name" as salt so the hash can't be re-used on different implementations.

Data Items Required...

1. A fixed "licensed to" name / email address or identifier
2. The number of projects licensed (you already have this)
3. The check-hash which is comparable using the two other data items

Answer 2

Funnily enough I know of a solution that does exactly what you want. The company I co-founded produces the OffByZero Cobalt software licensing solution.

When you're setting up your product in our system, you'd just need to add a Feature called something like 'MaxProjectNumber'. Then you can set a value for that feature on every licence you issue, and change it at will.

Answer 3

Are you looking for paid licensing options also? there are many

1. FlexLm licensing
2. http://www.xheo.com/products/licensing/?gclid=CI6tj9iVlJ8CFUUwpAodUgKEIA
3. http://www.x-formation.com/lm-x_license_manager/index.html
4. I think microsoft also has the licensing solution. again its paid and heavily priced.

A search on .NET licensing will yeild lot of licensing tools which can be added to your application. You can generate custom licenses like evaluation/node locked/floating license etc.

But most of them come at a price and at times can really agitate the customers during deployment issue. Most of the time a company which buys a legal license will buy more if needed instead of indulging in piracy. So keep the licensing as simple as possible so that end-user is happy using your application and genuinely feels like buying the software than you spending more time in coming up with some unique licensing technique instead of spending more time on the actual application.

Each year companies like microsoft/adobe etc spend so much on licensing and you eventually find piracted copies available on the internet. But at the end of the day, genuine customers do buy legal copies.