# Smart Contract-Enabled Secure Sharing of Health Data for a Mobile Cloud-Based E-Health System
## 2 Related Work  
There are many traditional solutions to solve the issue of the secure sharing of healthcare data in a cloud environment, such as mandatory access control, role-based access control, and trust-based access control [8]. Public key infrastructure has been widely utilized to provide secure authentication for healthcare data. In addition, some researchers have achieved fine-grained access control using different attribute-based encryption (ABE) methods [8,12]. Several studies have investigated blockchain technology's applicability in providing secure e-health data sharing. In [9], the authors adopted blockchain technology in an electronic healthcare system, e-health, to provide security services which can be shared among various users. Although the system proposed in [9] provides detailed explanations of the proposed framework, it lacks practical implementation, which is necessary to evaluate the proposed framework in real-world scenarios. Thus, several critical aspects of EHR sharing, such as adaptability, scalability, and access control have been overlooked. Furthermore, a data-processing approach based on blockchain technology was presented in [10] to ensure secure EHR exchanges across healthcare users. An autonomous solution based on blockchain technology was presented [10] to address the storage concerns related to the massive size of healthcare data. In [13], the authors presented a novel method that addressed the challenge of exchanging health data through cloud vendors. Smart contracts enforce an access control policy designed to restrict data access across untrusted parties, detect unauthorized entry into EHR stores, and enable healthcare data authenticity and monitoring. The authors in [14] measured the solution layout on Ethereum's actual test platform. The results were evaluated using smart contract costing analyses and vulnerability analyses to indicate an increase in data administration, secure data searching impartiality, and privacy concerns. Studies in [15,16] designed systems that combined the IPFS platform with blockchain technology to offer information sharing in IoT scenarios to overcome the challenge of maintaining large datasets on the blockchain. These designs make it easier for IoT devices to communicate and share information in unreliable contexts. In [17], the authors proposed a secure access control platform to facilitate the monitoring of patients' vital signs generated by IoT devices. The proposed scheme utilizes smart contracts on the hyperledger fabric framework to authenticate users and securely share data in the blockchain network. Similarly, the scheme proposed in [18] utilizes blockchain technology to control access to an IoT network and assigns a penalty to a misbehaving user. Both [17] and [18] do not provide a full picture of where the data generated from numerous IoT devices are stored because the block size in any blockchain technology is limited. [PERSON] et al. [19] implemented blockchain technology in a virtualized environment to safely transport EHR data between authorized organizations. Blockchain technology is significant in such situations because it offers available data that can be disseminated to all businesses in the network. This method is contaminated because all health exchange information is recorded in blockchain technology as a hash function. [PERSON] et al. [20] used pairing-based cryptography to create tamper-proof accounts of EHRs and enable physicians to incorporate them into blockchain operations. This can render patients' EHRs indisputable and shield them from inappropriate access. Using blockchain-based decentralized applications, researchers will also create safe payment protocols that allow patients and hospitals to pay dependably for diagnosis and storage services. Our proposed approach is effective and ensures security with minimal computational complexity, as shown by the security assessment and performance analysis. [PERSON] et al.