Internet of Things (IoT) has a huge attention recently due to its new emergence, benefits, and contribution to improving the quality of human lives. Securing IoT poses an open area of research, as it is the base of allowing people to use the technology and embrace this development in their daily activities. Authentication is one of the influencing security element of Information Assurance (IA), which includes confidentiality, integrity, and availability, non repudiation, and authentication. Therefore, there is a need to enhance security in the current authentication mechanisms. In this report, some of the authentication mechanisms proposed in recent years have been presented and reviewed. Specifically, the study focuses on enhancement of security in CoAP protocol due to its relevance to the characteristics of IoT devices and its need to enhance its security by using the symmetric key with biometric features in the authentication. This study will help in providing secure authentication technology for IoT data, device, and users.