Hi. I intend to make some software to be sold over internet. I've only created open-source before, so I have really no idea of how to protect it from being cracked and distributed as warez. Bearing in mind that I know like two programms that aren't either cracked or not really useful I decided that the only more or less reliable way may look like this:

1. Connect to a server and provide licensing info and some sort of hardware summary info
2. If everything is fine, the server returns some crucial missing parts of the program bound to that certain pc along with the usage limit of say 2 days
3. That crucial stuff is not saved to hard drive, so it is downloaded every time the program starts, if the programm runs more than 2 days, data is downloaded again
4. If the same info is used from different computers, suspend the customer account

What do you think about this? It may seem a bit to restrictive, but I'd better make less sales at first then eventually see my precious killer app downloaded for free. Anyways, first I need some basic theory/tutorials/guides about how to ensure that user only uses a certain Java app if he has paid for it, so please suggest some.

Thanks