# Privacy-Preserving Data Sharing in Telehealth Services
## 2 Literature Review  
[PERSON] et al. developed a novel encryption scheme to enhance the security of electronic health records (EHRs) within telehealth systems. The proposed model utilizes a unique patient ID to facilitate encryption and decryption, aiming to secure sensitive patient information effectively against unauthorized access. The research introduces an ECG signal-based random key generator, which strengthens the encryption process and ensures that each encryption key is distinct and tied to individual patient data, thereby enhancing privacy protections [18]. [PERSON] et al. develop a robust framework for securely sharing personal health records (PHRS) in telemedicine using private permissioned blockchain technology. The authors implement this system on Hyperledger Fabric and integrate a Byzantine Fault Tolerance consensus mechanism to ensure data integrity and privacy. Their model utilizes the Interplanetary File System (IPFS) for efficient off-chain data storage, which helps reduce blockchain load while ensuring secure and quick data access. Additionally, they incorporate smart contracts to provide granular access control, allowing patients to manage access to their data effectively. The results demonstrate the potential of their architecture to enhance secure sharing and access control within telemedicine, offering a significant contribution to the management of sensitive healthcare data [19]. [PERSON] et al. [20] propose an innovative framework for managing healthcare data via a cloud-based multi-authority access control system utilizing attribute-based encryption (ABE). Their model emphasizes the need for flexible and secure data sharing among multiple user domains while preserving the privacy of both data and access policies. The proposed system stands out by integrating a strategy that ensures policy privacy by only revealing policy attributes and hiding their values, which is critical for preventing unauthorized data inference. Additionally, the model incorporates a robust encryption mechanism to secure electronic health records (EHRs) across various healthcare stakeholders, significantly enhancing the system's capability to handle sensitive health data securely and efficiently. The study's findings indicate the potential of this framework to provide a scalable and secure data sharing environment, supporting the demands of modern telemedicine applications. [PERSON] et al. develop an innovative infrastructure to enhance the secondary use of health data through privacy-preserving federated systems. Their study outlines the implementation of Health Data Space (HDS) nodes that facilitate the versatile use of health data across different systems while maintaining high data privacy and security standards. The model leverages a federated approach where data are pseudonymized and harmonized using the Observational Medical Outcomes Partnership (OMOP) Common Data Model, ensuring data remain secure and interoperable across various healthcare providers and researchers [21]. [PERSON] et al. propose [22] a robust framework to enhance data security in e-health systems. Their scheme integrates forward-secure signatures and time-lock puzzles to authenticate and maintain the privacy of transmitted health data. This method ensures that data remain secure during transmission and provides mechanisms for patients to deny data association, enhancing both privacy and compliance with regulatory standards. The efficacy of their approach is demonstrated through comprehensive security assessments and performance evaluations. [PERSON] et al. critically evaluate an existing authentication scheme designed for Telecare Medical Information Systems (TMISs). They identify several vulnerabilities, including susceptibility to impersonation, replay, and tracking attacks. The authors propose enhancements to the authentication and key agreement processes to overcome these issues, presenting an improved scheme that boosts security and computational efficiency.