# Key Agreement and Authentication Protocols in the Internet of Things: A Survey
## 3 Security Protocols for the Internet of Things
The authors performed formal (using the ROR model and the ProVerif tool) and informal protocol analysis. Research has shown that the protocol is resistant to replay attacks, MITM attacks, and impersonation attacks and provides security features such as anonymity and untraceability. In turn, in [103], the authors proposed the SQXAP protocol that can be used to authenticate intelligent vehicles in cloud systems. The authors also performed formal (using the ROR model) and informal analyses for this protocol. Research has shown that the protocol is resistant to replay attacks, insider attacks, and MITM attacks, and provides security properties such as mutual authentication, anonymity, and untraceability. [PERSON] et al. in [105], [PERSON] et al. focused on industrial IoT (IIoT) security. The authors noticed that the low computing power of IIoT devices resulted in the low level of security implemented in such networks. The authors proposed a three-factor authentication and key-handshake protocol to solve such problems based on elliptic curve cryptography. The protocol can work on networks with one or more gateways. The authors confirmed the security of this protocol by using the ROM model and the Scyther tool. In turn, informal analyses confirmed that the protocol provides mutual authentication, session key agreement, forward and backward secrecy, user anonymity, and untraceability. Moreover,the protocol is resistant to stolen smart card attacks, replay attacks, privileged-insider attacks, desynchronization attacks, and impersonation attacks. The authors also compared their protocol and similar solutions for IIoT and obtained satisfactory results in achieving security attributes and energy consumption during communication and calculations. [PERSON] et al. in [106] also proposed an authentication protocol for IIoT. The proposed protocol uses the physically unclonable function (PUF) [107] chip and uses the Bloom [108] filter to preauthenticate and reduce computation and communication costs. The authors performed a formal safety analysis of the proposed protocol by using the Avispa tool and informal analysis. The research showed that the proposed protocol for ensuring the following security properties: mutual authentication, identity anonymity, and untraceability and forward and backward secrecy of session keys, and is also resistant to tampering attacks, replay attacks, simulation and forgery attacks, physical attacks, and desynchronization attacks. Moreover, the authors compared their protocol with other schemes regarding security and computational and communication costs with satisfactory results. [PERSON] et al. in [109] focused on industrial IoT solutions and proposed an authentication protocol for machine-to-machine communication. The authors tried to minimize the computational and communication load while increasing communication security. The authors used only XOR operations and hashing functions, and the shared symmetric key is only generated after two rounds of communication without human intervention. The authors carried out a formal (using BAN logic and the Avispa tool) and informal analysis of the protocol's security, showing that it is resistant to typical attacks occurring in IoT environments. In conclusion, the authors emphasized the advantages of a protocol that meets security properties with low computational and communication costs. Moreover, they noted that the protocol could be successfully implemented in other IoT domains. [PERSON] et al. in [110] have developed an authentication protocol for the cross-domain IoT environment. The protocol uses the elliptic curve digital signature algorithm, blockchain technology, and a specially designed cryptocurrency token to build trust between entities. The authors analyzed the safety of the proposed protocol. They showed that it is resistant to MITM attacks, replay attacks, revealing identity attacks, authority abuse attacks, and DoS attacks. In addition, they demonstrated its computing and communication performance. In turn, [PERSON] et al.