## 2 Related Work  
Eavesdropping, malicious node injection, and distributed denial-of-service attacks are among the most common types of IoT attacks. According to the Kaspersky report [4], 1.51 billion IoT breaches were recorded between January and June 2021 using only the Telnet remote access protocol. Unsecure communications, insufficient authentication, and password hygiene are the most common reasons for IoT breaches. In the recent past, researchers have emphasized on authentication mechanisms of IoT devices. The related works section discusses the various authentication protocols for IoT devices proposed by researchers. In this section, the literature is reviewed in three parts, the first part discusses the individual authentication mechanisms for IoT devices, the second part discusses the group authentication methods, and the third part discusses the authentication methods that use Blockchain technology. In one project, researchers presented an authentication mechanism for IoT devices and IoT servers using secure vaults. The proposed method works on multi-password shared secret-based mutual authentication [5]. Researchers in [6] used physical unclonable functions (PUFs) with elliptic curve cryptography (ECC) for device enrolment, authentication, decryption, and digital signature generation. In other research, a PUF was used along with two-factor authentication and IoT device wireless signal characteristics for secure authentication [7]. To safeguard IoT devices against cloning attacks, researchers proposed lightweight and privacy-preserving two-factor authentication for devices installed in open fields. In addition, PUFs have been utilized as authentication factors [8]. Researchers in [9] presented universal subscriber identity module (USIM)-based remote registration and group authentication for the 5G authentication and key agreement protocol (5G-AKA). Lightweight ECC was used in the proposed scheme in IoT devices in 5G cellular networks. A lightweight extensible authentication protocol (EAP) was used to develop authentication mechanisms for wireless network-connected IoT devices [10]. Researchers in [11] introduced an authentication entity between IoT sensors and receivers in a smart city environment. This authentication entity is responsible for authenticating all participating IoT devices before any data are transferred. A trusted authority-based lightweight authentication scheme using ECC and a secure element was proposed by researchers in [12] for an industrial IoT environment. In this part of the related work, group authentication mechanisms proposed by various researchers are discussed. A group authentication scheme for IoT-enabled mobile ad hoc networks is proposed by the authors in [13]. The proposed group's authentication mechanism is based on image hashing crosschecking of the identity image of a node that can be performed at the time of joining a group. Threshold cryptography-based group authentication (TCGA) [14] is proposed for authenticating a group of battery-constraint IoT nodes. In this mechanism, all IoT devices create their key pairs in the first phase and then a pseudorandom number is shared as a session secret in the group authentication phase. The combinatorial design is used to propose a group authentication mechanism with a fault-tolerant feature for IoT devices [15]. This authentication mechanism will operate even if some of the group members go down because of a fault. Elliptic curve cryptography and [PERSON]'s secret sharing-based group authentication technique were developed by researchers in [16] for resource-constraint IoT nodes. This technique can be used in both centralized and decentralized scenarios. PUF-based group authentication plus the key distribution protocol were developed using a factorial tree and the Chinese remainder theorem [17]. In this mechanism, each member of a group has to perform two encryption operations, one operation of decryption, four XOR operations, and three operations of hashing.