Massive Internet of Things (IoT) applications are characterized by a massive number of low-powered devices with small data storage. In those applications, authentication is very important to guarantee the origin of data produced by each device. With such characteristics, the authentication scheme needs to have small footprint and low complexity computation. Likewise, the number of authentication signaling needs to be significantly reduced to accommodate massive amount of IoT devices trying to connect to the network simultaneously, which is similar to Denial of Service (DoS) attacks. In 3GPP TR 33.899 V1.3.0, an architecture of the authentication system that consists of the aggregation nodes and the authenticators is proposed. The aggregation nodes receive the authenticated data from the devices and send the aggregated authenticated data to the authenticators. In this article, we discuss the possibility to implement more efficient authentication scheme for a massive Internet of Things (IoT) applications enabled in 5G networks. In particular, we analyze the performance of the system using some signature aggregation methods and identify the main research challenges in this area.