# Towards Secure Searchable Electronic Health Records Using Consortium Blockchain
###### Abstract  
There are significant data privacy implications associated with Electronic Health Records (EHRs) sharing among various untrusted healthcare entities. Recently, a blockchain-based EHRs sharing system has provided many benefits. Decentralized, anonymity, unforgeability, and verifiability are all unique properties of blockchain technology. In this paper, we propose a secure, blockchain-based EHR sharing system. After receiving the data owner's authorization, the data requester can use the data provider's keyword search to discover relevant EHRs on the EHR consortium blockchain and obtain the re-encryption ciphertext from the proxy server. To attain privacy, access control and data security, the proposed technique uses asymmetric searchable encryption and conditional proxy re-encryption. Likewise, proof of permission serves in consortium blockchains as the consensus method to ensure the system's availability. The proposed protocol can achieve the specified security goals, according to the security analysis. In addition, we simulate basic cryptography and put the developed protocol into practice on the Ethereum platform. The analysis results suggest that the developed protocol is computationally efficient. consortium blockchain model; EHRs; searchable encryption; proxy re-encryption Article  
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M.M. * Increasing massive data at high speeds: Medical information is large and annually increases in volumes by 20-40%. The challenges include not only how to obtain such a large amount of data from established IT systems but also how to maintain its privacy and protect its integrity while keeping third-party users highly accessible;
* Interoperability of cross-institutional data: To escape external attacks and threats, most existing healthcare systems are constructed in a closed area with a network security perimeter. Furthermore, the lack of medical information data interoperability presents a barrier for medical analytics that would require a great deal of clinical information. Besides, it poses drawbacks for patients who pursue improved care plans because their records are spread across many hospitals. In terms of sharing and access through EHRs, emerging technology based on breakthroughs and blockchain can bring encouraging solutions to secure patient data. Blockchain requires robust safety and privacy mechanisms for the interoperability, authentication, and exchange of health information in healthcare applications to follow the stringent legal requirements of the 1996 Health Insurance Portability and Accountability Act [2]. Blockchain was revealed in 2018 [4] to facilitate life in many areas with its distributed, safe and unchangeable structure. Many countries have had great success combining blockchain technology with eHealth systems. This technology has gained significant attention in recent years in the healthcare industry especially as a solution against a single point of failure problem. Smart contracts can make only authorized devices or users connect or access documented EHR data with multiple signatures between patients and service providers. This function ensures that patients can check the validity of EHR data while preserving their actual identity confidentiality. Even so, blockchain technology is not the best option for solving any problems in the industrial sector because it protects data integrity and availability, but it does not protect the confidentiality of data sharing. Therefore, cryptography is an appropriate solution for a secure data sharing-based blockchain, but it has a disadvantage with latency because when trying to encrypt all the data stored in the blockchain we need to decrypt it completely whenever we need specific data. To solve this problem many studies have proposed different solutions; one of them is Searchable Encryption (SE), which enables users to securely search for encrypted data without the need to decrypt all data [5].