Unmanned Aerial Systems (UASs) are being employed in many different applications, and with the increased usage security concerns become more accentuated. Communication links are core components of a UAS, and providing a secure communication channel is a necessity in which Authentication strategies play a major role. However, resource-constrained devices cannot adopt off-the-shelf security strategies that were not developed taking into account those devices' constraints. Because of that, new security strategies, including authentication, were purposed for these applications. In this paper, we analyze and compare two authentication protocols developed for WSNs and modified for UAV usage. Tests were performed analyzing time execution and CPU usage on security-specific operation such as hash tables and elliptic curve operations.