## 2 Literature Review  
To access the patient health record, URLs of the PHR are stored on the blockchain. However, the exiting approaches based on blockchain for patient health record or clinical record do not provide efficient access control for data search over the blockchain. As most of the recent research shows, blockchain is not search-friendly; looking up a specific record would be very slow with data increase. [PERSON] et al. [11] a novel method to manage blockchain-based human resource management. The method is based on the distributed ledger method (DL). The authors described the utilized privacy-preserving technique that is used to offer a transparent system while managing the human resource record. The public-private key pair was generated along with the organization ID, anonymity mapping, and hash [15]. The performances of the work were analyzed based on failure point identification, time, read-write latencies, and memory consumption. Meanwhile, it achieved better performance for all parameters except the time consumption. However, the execution is high. [PERSON] et al. [6] presented a novel deep blockchain-based trustworthy privacy-preserving secured structure (DBTPPS) to address the challenges such as privacy, trust, security, and centralization factors. The authors enclosed three modules: two-level privacy preservation module, trust management, and an anomaly detection module [16]. The first module was based on BC incorporated with autoencoder. The trustworthiness module composed a BC-based address reputation system. The last one was included in a deep neural network-based approach. The detection rate and accuracy of the presented work were 93.87 percent and 98.97 percent, respectively. However, they did not estimate the overall effectiveness of the proposed approach [17]. [PERSON] et al. stated a novel approach known as ant colony optimization (ACO) for privacy-preserving and for secure and reliable IoT data sharing; they adopted multi-kernel support vector machine along with elliptical curve cryptosystem (ECC). The protection and integrity were obtained by the blockchain. The experimental analysis depicted that the work attains better precision and recall and thus ensures security, privacy, confidentiality, and reliability. Nevertheless, the privacy of multiple components of encrypted datasets is difficult to attain. [PERSON] et al. [18] presented a novel method known as blockchain-based federated learning (BFL) approach to preserve privacy for the traffic flow prediction. The authors also described that the method can be used for the enabling of reliability and decentralized ad secured federate learning without the inclusion of a centralized model coordinator. The work provided better privacy protection and circumvented the data poisoning attacks. However, the communication overhead is a little higher in this approach. [PERSON] et al. [19] delineated a novel optimized trust model incorporated with a multilayer adaptive and trust-based weighting system. The authors presented numerical approaches to trust estimation clearly. The resiliency ad reliability of the method is maximum, however, the authors did not focus on the control-loop concept and their integration to achieve a decentralized IoT system. [PERSON] et al. [20] stated a novel blockchain-based trust management mechanism (BBTM) to provide better trustworthiness of the sensor nodes. The authors described better trust estimation and checked the estimation process. This work achieved better trust accuracy, resilience, and convergence against the attacks. However, there is no possibility for real-time application. In the traditional symmetric critical model, encryption is carried out using a symmetric key. The data owner divides data into some groups and then encrypts these groups using the symmetric key. Users who have private keys can decode the encrypted data. In this scheme, authorized users are listed in the ACL [21]. The major drawback of this scheme is that the number of keys grows linearly as the number of data groups increased.