Serverside in-app purchase verification libraries that do not require network access.
PLEASE NOTE: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. TAKE SPECIAL NOTE: IMPLEMENTATIONS ARE NOT GUARANTEED TO BE CRYPTOGRAPHICALLY SECURE. USE AT YOUR OWN RISK.
The goal is to create a reasonably serious implementation that is highly portable, not to be the most secure.