## 4 SSHies: An Era of Research
### Blockchain and Smart Contracts-Based Techniques in HIE Systems: A Background  
In [75], the authors proposed a mechanism using blockchain and IPFS (InterPlanetary File System), which disperses data among nodes, making health records tamper-free. The model must be patient-centric, allowing patients to grant and revoke access to records, share live data with doctors using wearable IoT devices in a protected environment, and store patient data in IPFS for immutability. The authors created an intermediate platform called Medical Health Record Chain (MHR Chain), where patients register and add medical record details, including PDF or image files, to the platform. This approach eliminates the need for third-party management for data storage, as data are stored in \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ref.** & **Year** & **Method** & **Data Set** & **Performance** \\ \hline
[58] & 2019 & \
\begin{tabular}{c} Gem Health Network, \\ OmniPHR, PSN) system, \\ Virtual resources, MeDshare \\ \end{tabular} & 70 papers &
\begin{tabular}{c} Discussion of \\ advantages and limitations \\ of healthcare blockchain \\ \end{tabular} \\ \hline
[59] & 2022 &
\begin{tabular}{c} PRISMA \\ \end{tabular} & 410 papers & Not available \\ \hline
[43] & 2021 & \
\begin{tabular}{c} Smart contract mechanism, \\ Permission-less and \\ Permissioned blockchain, \\ Consensus algorithms \\ \end{tabular} & Not available &
\begin{tabular}{c} Access control, \\ authentication and \\ authorization, storage \\ \end{tabular} \\ \hline
[60] & 2021 & \
\begin{tabular}{c} Groups of antecedents \\ \end{tabular} & 357 individuals &
\begin{tabular}{c} Patient attitude, \\ privacy and security \\ \end{tabular} \\ \hline
[61] & 2022 & \
\begin{tabular}{c} Blockchain, IOT, \\ Smart contract, Federated \\ learning \\ \end{tabular} & NA &
\begin{tabular}{c} Advantages evaluation of \\ blockchain traceability \\ \end{tabular} \\ \hline
[41] & 2022 & \
\begin{tabular}{c} Screening of \\ blockchain papers \\ \end{tabular} & 22 papers &
\begin{tabular}{c} Quality: high (3/22), \\ moderate (9/22), \\ low (10/22) \\ \end{tabular} \\ \hline
[42] & 2020 & Qualitative synthesis & 70 papers &
\begin{tabular}{c} Improvement of \\ patient engagement, \\ information access \\ \end{tabular} \\ \hline
[73] & 2023 & \
\begin{tabular}{c} Design science \\ research methodology \\ \end{tabular} & AWS &
\begin{tabular}{c} Throughput = 115 T/s \\ VS 10-20 Bitcoin; \\ Latency = 118 ms \\ VS 10.12 mn Bitcoin \\ \end{tabular} \\ \hline
[74] & 2021 & \
\begin{tabular}{c} Blockchain-based \\ techniques analysis \\ \end{tabular} & NA &
\begin{tabular}{c} Latency = 133 ms \\ Vs 10 mn Ethereum \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Integration of blockchain technology into HIE systems: a summary. IPFS, a distributed ledger, and the hash is stored in the blockchain, ensuring resistance to manipulation. The authors of [76] devised a blockchain architecture comprising four modules: a creation module for NFT creation, a linkage module to connect local patients' accounts with their NFTs, an authentication module enabling patients to authorize healthcare providers to access their tokens, and an exchange module for facilitating the HIE process and token validation via SSI. They opted for the Quorum blockchain, leveraging its Raft-based consensus mechanism to enhance scalability and efficiency. All sites must furnish a blockchain node, which runs blockchain services and necessitates permission from the blockchain originator. The approach proposed in [77] involves a combined encryption and decryption architecture (CEDA) employing a hybrid double encryption mechanism utilizing AES and RSA algorithms to encrypt medical records, resulting in secured encrypted medical records (SMeR). A blockchain architecture was employed to store the hash value of the encrypted EMR and to verify its accuracy using a triple encryption mechanism.