## 2 Literature Study
Bloom filter is probabilistic in nature, which means at times it can generate highly false-positive results. This issue is tackled by limiting the number of hash functions. Still, the processing time of hash functions is quite long in the proposed architecture, making it less effective, particularly for military networks. A privacy-preserving data sharing technique involving federated learning has been proposed based on blockchain [19]. The proposed system depends on machine learning to train a global data model. It is used for two types of transactions, i.e., retrieving data and sharing data. Because of storage limitations and computation resource restrictions, the original data is stored with the owners of the data while the identity of data providers is stored on the blockchain. The proposed system works effectively in data sharing but it does not reveal how the identity of data providers can be preserved. Limited efforts have been observed in the literature that propose security and privacy solutions based on blockchain. Automotive security and privacy framework using blockchain based on changeable private keys is proposed [20], but it relies heavily on the traditional encryption algorithm. An open platform for exchanging messages between service providers and drivers based on blockchain [21] has been proposed. A self-pseudonym generation technique is introduced. The pseudonyms are stored on the blockchain to ensure the security and privacy of the vehicular network [22], but the proposed system relies on the traditional Ring Algorithm, consuming a lot of time in computation. The privacy-preserving mechanism for multimedia sharing has been proposed based on blockchain that depends on pseudonyms for hiding the identities of vehicles, roadside units, and users [4], but it relies on the centralized trusted authority for the issuance of pseudonyms. A decentralized blockchain-based architecture for VANET has been proposed for tackling distrust among vehicles and infrastructure [23]. The proposed system uses a dynamic encryption technique known as threshold encryption and k-anonymity unit algorithms. The k-anonymity unit algorithm takes time to calculate sub-identities for vehicles, making the proposed system less effective in real-time scenarios. A blockchain-based authentication protocol has been proposed for the cooperative VANET utilizing the digital signature algorithm RSA-1024 [24]. The proposed system is claimed to ensure the confidentiality, integrity, non-repudiation, and privacy protection of IoVs. It successfully achieves privacy protection and the security of IoVs. However, the performance of the system becomes affected because of the use of a cooperative transmission protocol. The throughput of the system is reduced further if the number of vehicles continues to increase. Signatureless public key infrastructure has been implemented on the blockchain, relying on message ratings and credibility to mitigate network attacks [25]. The performance of the proposed system is quite a stack since the authentication process takes a lot of time. It requires authentication from different blockchains used within the proposed system. This reduces the communication setup and, hence, produces delays in valid communication. A privacy protection system has been proposed based on blockchain for IoV that has two-way authentication with a key agreement algorithm designed on random numbers [26]. It ensures the confidentiality of the security information. However, the proposed system relies on the PoW consensus algorithm, which consumes a lot of computing resources, forcing the system to create undesired delays in generating responses. A decentralized and location-aware traffic management system has been proposed for protecting data integrity and privacy using Zero-Knowledge Range Proof (ZKRP) based on multiple blockchain environments [27]. The proposed system introduces the concept of gateways, which reside in between two adjacent blockchains that help in switching the traveling vehicles from one blockchain to another.