Internet of Things (IoT) is the domain of interest for the researchers at the present with the exponential growth in technology. Security in IoT is a prime factor, which highlights the need for authentication to tackle various attackers and hackers. Authentication is the process that uniquely identifies the incoming user and this paper develops an authentication protocol based on the chebyshev polynomial, hashing function, session password, and Encryption. The proposed authentication protocol is named as, proposed Elliptic, chebyshev, Session password, and Hash function (ECSH)-based multilevel authentication. For authenticating the incoming user, there are two phases, registration and authentication. In the registration phase, the user is registered with the server and Authentication center (AC), and the authentication follows, which is an eight-step criterion. The authentication is duly based on the scale factor of the user and server, session password, and verification messages. The authentication at the eight levels assures the security against various types of attacks and renders secure communication in IoT with minimal communication overhead and packet-loss. The performance of the method is analyzed using black-hole and Denial-of-service (DOS) attacks with 50 and 100 nodes in the simulation environment. The proposed ECSH-based multilevel authentication acquired the maximal detection rate, PDR, and QOS of 15.2%, 35.7895%, and 26.4623%, respectively in the presence of 50 nodes and DOS attacks, whereas the minimal delay of 135.922 ms is acquired in the presence of 100 nodes and DOS attacks.