Typically what you want to do is pick some data that you want to include in the key like who owns it and when it expires, possibly even some small pieces of code your application needs to work properly (thus making it hard to make it work without the key). Then use a digital signature scheme like RSA to digitally sign the key with your company's private key. Distribute the public key with the application executable. Then when you load the key, just verify the signature is valid and then use the data contained in the key. A 1024 or 2048 bit key should be plenty for this.
Of course no matter how sophisticated your code is someone will always be able to break it or get around it. So the question you have to ask yourself is how difficult do you want to make it (keeping in mind more difficult schemes are harder to code and maintain for you)? There is a point of diminishing returns, usually that is pretty low. As long as the program won't work without a key, and the key is complicated enough that you can't fake one (or change the expiration date etc) with a hex editor then you are probably fine.
