## 1 Introduction
In addition, this protocol has a lower degree of decentralization which will change the nature of ITS-VANETs. Another example is interoperability: when it comes to transportation, the DLT system should be compatible with a wide range of systems, technologies, and platforms to ensure that data are shared effectively among all parties involved. With the absence of Layer 0 in the crypto-networks and due to the importance of interoperability to an ITS system, the choice of a certain ledger should be based on the requirement of ITS. Security and Privacy: Data integrity and confidentiality must always be maintained by the system to prevent any unwanted changes or disclosures to private information. Strong encryption, access restriction, and other privacy-protecting measures fall under this category. For example, Ethereum provides strong cryptography and a medium latency which is acceptable. However, with the growth of VANETs, the network will encounter some throughput and routing issues due to time adjustment (used in Bitcoin) and the huge amount of operations which take place in Ethereum to reach agreement. In [25], a Blockchain-based Conditional Privacy-Preserving Authentication (BCPPA) protocol employs key derivation and blockchain technology to enhance VANET authentication and privacy. BCPPA utilizes Ethereum smart contracts to secure vehicle communication over VANET. The costly Elliptic Curve Digital Signature Algorithm (ECDSA) can be replaced with a modified version or another Public Key Infrastructure (PKI)-based signature with bulk verification to increase efficiency. Using blockchain technology, the BCPPA protocol provides conditional privacy-preserving authentication and decentralized, tamper-proof VANET communication. Even though smart contracts are hosted in a secure blockchain, limiting the process of securing the communication to a programmable transaction will centralize the process in addition to the centralization level of Ethereum. Latency: Traffic management, navigation, and V2V communication are just a few examples of real-time ITS applications that require low latency. Transactions and data exchange on the DLT system must be rapid. The nature of ITS-VANETs is direct and rapid communication. When using a DLT-based framework, the latency must be taken into account. In [26], the primary contribution of this work is to propose a secure 5G-ITS through the use of blockchain technology to evaluate trust against potential attacks. To accomplish hierarchical trust evaluations and protect the privacy of users, federated deep learning is used to evaluate the trust of ITS users and task distributers. In order to guarantee the efficay and accuracy of trust evaluation, hierarchical incentive mechanisms are also designed to implement reasonable and fair rewards and punishments. Hyperledger is used to implement frameworks and is well known for its power consuming and high resource usage. The nature of DLT-based IoV is decentralization while ensuring fairness and decentralization. In [27], a Public, Special, and Supreme framework is presented. The \"Public\" blockchain server is responsible for service-related data transmission, verification, and storage. It is a shared blockchain server with limited storage capacity. Once the public blockchain's memory is complete, it will replace its own data within the blockchain. Similarly to the public blockchain server, the \"Special\" blockchain server displays dynamic features. Specifically, the \"Supreme\" blockchain server is used to store all network-participating vehicle information. Each data transmission detail of the intelligent vehicle is securely preserved and processed in the supreme blockchain. The nature of the required operation for DLT usage is not satisfied, since the three servers reduce the decentralization and increase the vulnerability toward Single-Point Failure (SPF). Consensus Mechanism: Security, decentralization, and performance are all factors that should be considered while deciding on a consensus process.