Global Navigation Satellite Systems (GNSS) are a key enabler for many new technologies, ranging from autonomous vehicles to shared mobile devices. In order to ensure high precision for those applications, GNSS augmentation systems are needed to provide correction data to reach a precision that is in the order of centimeters. Those systems can be provided as paid services where correction data are broadcast over a satellite link. In order to protect those systems and restrict their access only to paid users, encryption mechanisms must be adopted. SPARTN is an open industry standard for GNSS augmentation that has been specifically designed for supporting encryption, while saving bandwidth on the satellite link. In this paper, we propose APBE (Anti-Piracy Broadcast Encryption), a method to enhance the SPARTN security by providing protection against pirate customers that is specifically tailored to minimize bandwidth and storage. The proposed approach is demonstrated to be feasible via a real proof-of-concept implementation based on an embedded system. APBE is a candidate mechanism to be included in the future versions of SPARTN.