Activation Proof: Similar to a signed license key, we also offer the ability to generate a \"proof of activation\" for use in offline environments. A device can be activated using a license management portal, or a proxy license server, and the activation proof can be generated and delivered to the offline device. Your software can cryptographically verify that the device was indeed activated, all without requiring that the device connect to the public Internet.
This is achievable by product activation (Windows is a good example). Basically, for a customer with a valid license key, you need to generate some \"activation data\" which is a signed message embedding the computer's hardware id as the signed data. This is usually done over the internet, but only ONCE: the product sends the license key and the computer hardware id to an activation server, and the activation server sends back the signed message (which can also be made short and easy to dictate over the phone). From that moment on, the product does not check the license key at startup, but the activation data, which needs the computer to be the same in order to validate (otherwise, the DATA would be different and the digital signature would not validate). Note that the activation data checking do not require verification over the Internet: it is sufficient to verify the digital signature of the activation data with the public key already embedded in the product.
Being a shareware author and longtime member of ASP myself i think you are going into the wrong direction with your solution. The only way to make this workable is with a hardware device as already suggested. This or constant online activations is the only way if you want to be sure and your product is so good and without competitors that your customers will still use it. 1e1e36bf2d