LabWindows/CVI
Software protection dongle
How many times does he expect to sell this application?
I can't recommend you any specific dongle and most dongles are not that hard to integrate into any application through their SDK, especially if you can do that from C (a given in CVI).
The real difficulties come from other issues:
- How do you go about charging? Invoice, online or personal money transfers?
- Processing of this is usually rather cumbersome, arranging payment services (Stripe or other online payment service, money transfer, bank accounts outside of your own country are all things that you need to properly asses and setup).
- Most customers are vary to do such arrangements. Subscription is always tricky and puts a customer at the mercy of the provider. Arbitrary price changes can put a business into a very bad situation. Basically subscription is a hostage situation that only works if you trust the provider to not suddenly go crazy. Who in his good mind does that nowadays? What if your customer goes out of business? Who will take over responsibility for maintaining the application and the licensing service?
If your customer really wants to go down this path, explain to him that the initial effort will be considerable, and mostly beyond the technical issue of integrating any license system into his application. You could look at the NI 3rd party licensing toolkit. It's mostly tailored to LabVIEW solutions but I believe there was a version for CVI too. By hosting the application on the NI tools network you would get a fairly easy setup, with licensing and payment processing handled for your customer. But NI takes 30% of the sales price for that.
You can go more self made by integrating the Software Key (www.softwarekey.com) solution. That provides you with a concise licensing solution that can integrate into your application. You have the choice to let the licensing and payment be handled on the Software Key servers for a nominal percentage of the sales proceeding or license their Solo Server to run on your own premise or cloud service and handle everything yourself. It will be a considerable effort and require regular maintenance and support from someone who understands about network infrastructure.
Or you can try to look into Sentinel from Thales. They have many solutions and I haven't really worked with any of them. The old style USB dongles are nowadays considered legacy but they still provide them. Most providers want you to invest into their cloud based solutions, easy and universal to use for you but also a guaranteed regular revenue stream for them!
Whatever you choose, expect trouble. And integrating whatever API such a licensing solution provided into your application is usually by far the most simple trouble of it all. The other additional struggles come with payment and license maintenance, keeping your solution up and running in a severe security challenged environment, and convincing your customers that you are a trustworthy party to deal with and if you sell it as subscription, that you won't try to hold them hostage or go out of business at the most inconvenient moment for them.
