# Privacy-Preserving Data Sharing in Telehealth Services
## 3 Method
* f: computation function that can be performed on encrypted data. * R: encrypted result of the computation. **Step 4: Access Control and Permission Management**  
Using smart contracts on the blockchain, access permissions Pi are checked before any function f can be executed on data, enforcing strict compliance with the patient's preferences  
* **Equation**: if (Pi) then execute (f)
* **Explanation**:  
* Pi: permission set by the patient. * f: function or access request. **Step 5: Data Integrity and Auditing**  
Each transaction Bt on the blockchain is auditable, and its integrity can be verified, ensuring the data have not been tampered with, and access patterns are transparent. * **Equation**: verify(Bt)
* **Explanation**:  
* Bt: blockchain transaction. * Verify: this function checks the integrity of blockchain transactions. **Step 6: Compliance and Reporting**  
Smart contracts can be programmed to automatically ensure that all transactions B comply with specified rules, such as the HIPAA or the GDPR, and can facilitate automated reporting to regulatory bodies. * **Equation**: comply(B, rules)
* **Explanation**:  
* B: entire blockchain ledger. * rules: set of regulatory compliance rules. Figure 1 illustrates the comprehensive algorithm for secure healthcare data management within telemedicine systems. This sequence diagram systematically maps out the interactions among various actors--patient, healthcare provider, blockchain, smart contract, SMPC Engine, Audit Module, Regulatory Body, and Compliance System. Each actor's role is precisely defined, ensuring a seamless data flow and decision-making processes. The patient, as the primary data owner, initiates the sequence by encrypting their health information before sharing it with healthcare providers. This encryption ensures that the data remain protected at all stages of the interaction, maintaining privacy from the outset. The healthcare provider is responsible for accessing and utilizing patient data within the constraints set by the patient and regulatory requirements. Data access is facilitated through smart contracts, which are deployed on the blockchain network. These smart contracts automate the enforcement of predefined rules for data access, ensuring that only authorized parties can retrieve and interact with sensitive information. The use of blockchain not only decentralizes data management but also adds a layer of immutability, ensuring that all transactions and modifications to the data are permanently recorded and can be traced back if necessary. This provides transparency, accountability, and trust in the system. The SMPC (secure multi-party computation) Engine plays a critical role in allowing computations on encrypted data without revealing the underlying information. This enables various healthcare providers or researchers to collaborate on patient data analysis while maintaining the confidentiality of the patient's personal health information (PHI). This is particularly important in research and diagnostic scenarios, where insights can be derived without violating privacy. In addition to the core actors, the Audit Module continuously monitors the system's transactions, verifying that all actions comply with the security protocols. This module conducts regular checks to ensure that all data exchanges and computations follow the required encryption standards and that no unauthorized access attempts occur. The auditing process is crucial for identifying any potential vulnerabilities or breaches early on, allowing healthcare providers to respond proactively. Moreover, it offers a way to document compliance with data protection laws, making it easier to demonstrate adherence to regulatory standards during audits by external bodies. The Regulatory Body plays a key oversight role by periodically reviewing the system's operations to ensure compliance with healthcare regulations such as the HIPAA, the GDPR, and other jurisdiction-specific laws.