# Key Agreement and Authentication Protocols in the Internet of Things: A Survey
## 3 Security Protocols for the Internet of Things
in [111] confirmed this protocol's computing and communication advantages. However, they showed that it only allows one-way authentication and adds to the burden of certificate storage. [PERSON] et al. in [112] have proposed a mutual authentication protocol with key handshaking based on blockchain, elliptic curves, and bilinear pairs. The authors replaced the centralized CA with the registration authority to avoid single-node failure and some attacks. In addition, the key recovery and key update scheme use the Lagrange interpolation method [113]. The authors formally confirmed the safety of the proposed protocol by using the ProVerif tool and the ECK model [114]. Informal security analyses have shown that the proposed protocol is resistant to typical IoT attacks. Moreover, the authors noted that this protocol's computational and communication overhead is negligible. However, [PERSON] et al. in [115] pointed out that the protocol barred by [PERSON] et al. in [112] user anonymity is prone to insider attacks. [PERSON] et al. in [116] proposed a two-way, mutual authentication and key agreement protocol. The protocol involves four phases: initialization, registration and generation of secret keys of long duration, key authentication and reconciliation, and updating public and private keys. The authors, using the ROR model, BAN logic and the Scyther tool, confirmed the correctness and safety of the proposed protocol. Additionally, the informal analysis showed resistance to this protocol to replay attacks, MITM attacks, device capture attacks, privilege-insider attacks, KCI attacks, known specific temporary information attacks, impersonation attacks, and known-key attacks. In addition, these analyses showed that the protocol provides anonymity and untraceability and perfect forward/backward secrecy. The authors also assessed their protocol in terms of communication, calculation costs, and energy consumption, and they obtained satisfactory results in comparison with similar solutions. [PERSON] et al. in [117] proposed a lightweight protocol for authenticating and negotiating session keys. The proposed protocol uses shared secret and elliptic curve public key technology and is based on the CoAP framework [118]. The techniques used to ensure the security and anonymity of devices and users. The authors verified the performance and safety of the proposed protocol by using the Dolev-Yao adversary model [119] and the CPN Tools tool [120]. The analysis showed that the protocol provides the following security properties: confidentiality, data integrity, mutual authentication, perfect forward and backward secrecy, device anonymity, and unlinkability. The protocol is resistant to impersonation attacks, MITM attacks, privileged-insider attacks, replay attacks, KCI attacks, desynchronization attacks, and DoSs attacks. Moreover, the authors compared their protocol with other schemes regarding security and computational and communication costs with satisfactory results. [PERSON] et al. in [121] proposed another two-factor authentication and key agreement protocol for IoT environments. The proposed protocol consists of the predeployment phase, the IoT device registration phase, and the login and authentication phase. The authors distinguished two roles: IoT devices and a server. The IoT device must register on the server. Further communication between these devices takes place by using a session key generated by the server. The authors tested the security of the proposed protocol by using the ROR model and the BAN logic. Studies have shown that the protocol is resistant to privileged-insider attacks, known temporary information disclosure attacks, stolen verification attacks, IoT device simulation attacks, and physical IoT device capture attacks. In addition, the protocol provides the perfect forward secrecy property. Moreover, the authors compared the proposed protocol with similar security and computational and communication cost solutions, obtaining satisfactory results. Another mutual authentication protocol was proposed by [PERSON] et al.