## 2 Related Work
[31] designed a \"federated identity management (FIdM)\" system in order to assist in improving privacy and user authentication in the IoT deployment, where an IoT device accesses services from a service provider. Their approach was lightweight as it required low computational cost due to symmetric cryptographic operations. They applied their proposal to a cashless toll system environment. [PERSON] and [PERSON] [32] designed a \"lightweight and privacy preserving two factor authentication\" scheme in which physical security was included. In their proposal, an IoT device and a server mutually authenticated each other for accessing services in the IoT environment. However, their scheme needed more computational cost due to fuzzy extractor generation and reproduction functions [33]. In order to design an access control and security policy, [PERSON] and [PERSON] [34] designed a mutual authentication scheme between IoT devices. Though their scheme was lightweight due to symmetric cryptographic operations, it did not preserve device anonymity and untraceability properties. Group key management (GKM) is considered as another important security aspect in the IoT environment, which helps with assigning IoT devices into predefined groups in the network. After that, key management is essential within each group and also among various groups in order to improve efficiency and security in the IoT environment. For this issue, [PERSON] and [PERSON] [35] designed an efficient GKM policy in an IoT deployment. Their approach also permitted joining and leaving the devices in a group dynamically in the IoT environment. Their approach was lightweight as it relied on the \"cryptographic hash function\" and symmetric cryptographic operations. [PERSON] and [PERSON] [36] pointed out that \"unanimous consensus\" is extremely essential in the IoT environment for cyber security purposes. They presented a lightweight adaptation of the \"Internet Key Exchange Version 2 (IKEv2)\" for the IoT deployment, called TinyIKE. With the help of TinyIKE, they were able to solve the key management issue for several IoT protocols by applying a single IKEv2 based approach. TinyIKE relies on certificates, elliptic curve cryptographic techniques, as well as symmetric cryptographic techniques. [PERSON] et al. [3] recommended an ECC based user authentication protocol for IoT applications that can be used in the coming future. However, [PERSON] et al. [37] highlighted that [PERSON] et al. 's method did not protect against impersonation attack and also it did not preserve the untraceability property. Moreover, [PERSON] et al. 's scheme [3] was expensive in computation and communication. Recently, [PERSON] et al. [38] presented a \"certificate based device access control\" scheme applied to IoT communication to mitigate the security problems and limitations of the existing authentication and access control protocols. Their scheme the preserved anonymity property. [PERSON] and [PERSON] [39] proposed a lightweight user authentication protocol that can be applied to healthcare services in the cloud-IoT environment. However, their scheme was insecure against privileged-insider attack during the registration of medical professional, where the password of the medical professional was easily guessed by an attacker with the help of stolen smart card attack and registered information supplied by the medical professional to the gateway node. Moreover, their scheme did not provide the sensor node anonymity property and session key security under the Canetti and Krawczyk (CK) adversary model [40] (discussed in the threat model in Section 3.2). [PERSON] et al. [41] designed an authentication protocol that utilized IoT based architectures combined with cloud servers. Though their scheme was lightweight in nature, [PERSON] et al. [42] pointed out that [PERSON] et al. 's scheme [41] was vulnerable to various attacks, such as privileged-insider attack, man-in-the-middle attack, replay attack, and user impersonation attack. Furthermore, [PERSON] et al. also showed that [PERSON] et al.