Table 3.

Features of blockchain and smart contract methodologies for technical CCAM challenges.

Ref	Challenge	Technology	Advantages	Disadvantages	Impact
[44]	Security	Blockchain—PoW and PBFT	Protection against attacks on centralized systems and malicious RSUs Protection against brute force attacks based on asymmetric encryption and signature verification techniques.	With a small number of involved RSUs in the network, there is an increased possibility of malicious tampering; thus, the system is unstable.	Data collected from the RSUs of a VANET are protected by brute force attacks through distributed data storage based on blockchain technology and from the exchange of data between RSU and vehicles using smart contracts, making the network security more suitable for CCAM environments
[45]	Security	Blockchain—PoW	It defines those parameters that ensure the secure transmission of messages in VANETs located in a limited geographical area.	Even with a small percentage of malicious nodes, if the delay time of messages from malicious nodes is less than “good” nodes, the 51% attack is quite possible.	The blockchain network is protected against malicious nodes, even if these “bad” nodes form a group of miners, due to the guidelines and parameters that are defined.
[46]	Security	Permissionless Blockchain and Smart Contracts (Ethereum)—PoW & PoS	Provides security against various types of attacks, such as hijacking, 51% resistance to attacks, DDoS, man-in-the-middle	The average packet delay of the data is affected by changes in the average speed of the vehicles.	Presentation of the new CPPA protocol for establishing secure communications in VANET networks, utilizing blockchain technology.
[47]	Privacy	Blockchain—PoW	Efficient methodology reducing the dependency on the CA and the burden on vehicle authentication	It is not a purely decentralized solution because it is based on a relatively small number of servers in the cloud.	Mechanism for adding extra protection against transmission of false messages in vehicle transactions in V2V and V2I communications that guarantee authentication and nonrepudiation in combination of blockchain and PKI.
[48]	Decentralization	Blockchain—PoQF	Reliable mechanism in case of knotting. Fewer validation losses than other consensus mechanisms.	The voting mechanism increases latency. It is impervious to 51% majority attacks.	A novel consensus mechanism for VANET, differing from existing systems, where node votes on road events and accidents are used. Security protection against collusion attacks is provided through a blockchain-based PoQFconsensus mechanism.
[49]	Sensing Accuracy	Permissioned Blockchain and Smart Contracts—DPoS	Improvement in position accuracy is possible even when access to reference points is interrupted	It does not consider random errors in positioning	Integrating DNNs with blockchain and smart contracts to enhance and share location accuracy, eliminating the need for centralized management by utilizing mobile edge computing nodes and vehicles.
[50]	Audit	Blockchain—PoS	It reduces the need for processing power in vehicles	Stored feature policies are not dynamic and do not change.	Definition of quality characteristics stored in the blockchain network for evaluating and recording vehicle announcements. The blockchain safeguards nodes against alteration and tracking attacks.