Abstract
In this paper, we propose the authentication server system that prevent hacking in In-app billing applications. And we also propose the methods to verify electronic receipt for the payment of internal app payments and to check the integrity of the applications. Then we designed the payment metabolic system that checks between products-offer list and paid subscription if payment system is hacked with new hacking technologies different from existing ones. And then we implemented proposed authentication system and experimented with about 10,000 average internal application payments per an hour. It shows that proposed system has defensive techniques that counter attacks against in-app billing but it takes more than 0.8916 seconds than no-certification system that is considered as relatively short time.