Your aim should be to "keep honest people honest," not to prevent your app from being cracked. As in, a simple license and trial mechanism that may not be bull

Your aim should be to "keep honest people honest," not to prevent your app from being cracked. As in, a simple license and trial mechanism that may not be bullet proof but is enough such that an uninstall and re-install of the trial is not enough to allow them to use it for free forever, and that a license key needs to be entered somewhere to remove the trial limit restrictions. You can invest time effort and money in stopping your app being cracked, but that's time effort and money your not spending making your paying users's lives better. Most people do not visit Warez sites to find cracked versions of software, and most people who do visit Warez sites never pay for software anyway -- you won't lose money to these people. A simple license key that validates locally is the easiest solution -- no dialing home, nothing overly complex. Any extra effort needs to be warranted -- as in, you're losing $1000s a week because of lost users who would have paid but don't because they can use your app without a valid license.