## 3 Security Implications and Fundamental Approaches of Blockchain-Based Data Storage Methods
### Blockchain-Based Data Integrity and Traceability Solutions
#### 3.5.3 Achieving Flexibility with Hybrid Storage Solutions
Its integration with existing hospital management systems has shown significant improvements in data accessibility and integrity, and the adoption of standardized frameworks may enhance real-time data sharing while maintaining patient privacy, facilitating hybrid integration [151; 166; 168; 152]. Additionally, advanced security technologies such as homomorphic encryption are further strengthening health record security [110; 135]. In the financial sector, transaction accuracy and data integrity are paramount. On-chain solutions, using distributed ledger technology (DLT) and advanced cryptographic security mechanisms, ensure the protection of financial transactions. Platforms like Hyperledger Fabric enable immutable storage of credit histories and transaction records within the decentralized finance (DeFi) ecosystem, but complex regulatory requirements and high transaction costs limit widespread adoption [43; 100]. A practical implementation of this is found in JPMorgan's Quorum blockchain, which enables secure interbank set \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Reference Number** & **Sector** & **Recommended Storage Method** & **Application Domains** & **Security Need** & **Security Advantages** & **Disadvantages** & **Sample Projects** \\ \hline
[151; 170] & Healthcare & Hybrid (Blockchain + IPFS and Smart & Patient data, Deffix and Smart (EHR) & High electronic health records & Ensures privacy and security, legal data protection & Integration challenges & MedRec, FHIRChain \\ \hline
[43; 100] & Finance & On-chain (DLT and Cryptography) & Credit history, transaction records & Medium & Provides data integrity and immutability & Costly and slow transaction speeds & Hyperledger Fabric \\ \hline
[7; 49; 174] & Education & Off-chain (Blockchain + IPFS) & Sharing certificates, and diploma, and degree & Low & Cost effectiveness, high data access speed & Dependency on centralized systems & IPFS Education Projects \\ \hline
[103; 171; 172] & Supply Chain (Blockchain + IoT) & Hybrid (Blockchain + IoT) & Product traceability, traecability, logistics management & High & Traceability, fast data processing & Complex configuration & IBM Food Trust \\ \hline
[104; 175; 105] & Public Sector & On-chain (Self-Sovereign Identity and Digital ID Management) & Authentication, records & High & Transparency, secure access & High transaction cost and speed limitations & Civic cost and speed limitations & \\ \hline
[50; 51] & Internet of Things (IoT) & Hybrid (Blockchain + Cryptographic Authentication) & Sensor data, location data Authentication & Medium & Efficiency, low cost & Lack of data integrity and traceability & Helium Network \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Sectoral perspective on data security and applications of on-chain, off-chain, and hybrid data storage methods. tlements and cross-border transactions by leveraging permissioned DLT. This showcases how blockchain enhances security in financial data storage while overcoming traditional banking inefficiencies. Future Layer-2 solutions may help reduce scalability and transaction cost concerns, promoting broader blockchain adoption in finance [19; 20; 97]. Optimistic Rollup and ZK-Rollup technologies will enhance transaction speeds and efficiency in DeFi ecosystems [95; 96]. In education, blockchain ensures the immutability of academic certificates and diplomas, helping to combat fraud and enhance reliability in recruitment processes. Off-chain solutions, integrating IPFS-based education projects, enable secure document storage while allowing authorized users to access encrypted records [7; 49]. However, integration with centralized education systems and long-term storage costs present challenges [7; 174]. The University of Nicosia, one of the first institutions to adopt blockchain for academic credentials, has successfully issued digital diplomas that are verifiable via blockchain explorers.