# Blockchain-Enabled Privacy-Preserving Ecosystem for DNA Sequence Sharing
## 4 Evaluation
### Security Vulnerabilities and Mitigation Strategies  
Although blockchain technology strengthens data integrity and transparency, it is not immune to security vulnerabilities, especially in biomedical data applications. We analyze potential threats to our system and the mitigation strategies in place:  
* Blockchain Endpoint Security: One well-known vulnerability is at the user endpoint--if an attacker compromises a user's device or wallet, they could steal private keys and impersonate that user [27]. In our system, this risk is mitigated by the use of trusted wallet software (MetaMask ([[https://metamask.io/](https://metamask.io/)]([https://metamask.io/](https://metamask.io/)), accessed on 17 February 2025)) for identity transactions and by encouraging users to keep their Fabric private keys secure (e.g., downloaded keys are protected by passwords). We assume users follow best practices; in future work, hardware wallets or multi-factor authentication could be integrated for additional safety. * Smart Contract Vulnerabilities: Bugs or logic flaws in smart contracts/chaincode can lead to exploits. We addressed this by keeping the chaincode logic simple and rigorously testing each function. For example, identity contracts only allow trusted authorities to create new identities, and the Fabric chaincode checks that transactions are properly signed by certified entities. We also benefit from Hyperledger Fabric's en dorsement policies that require multiple peers' approval for transactions, reducing the risk of a single malicious peer affecting the ledger. Nevertheless, we remain aware that smart contract vulnerabilities in healthcare blockchain systems have been reported [28]. As a precaution, our contracts were audited for common issues (reentrancy, overflow, improper access control) and deployed on test networks before production. * Network Attacks: Public blockchains face 51% attacks or Sybil attacks on their peer-to-peer networks [27]. In our consortium blockchain, membership is permissioned--all nodes are known organizations--which largely prevents Sybil attacks (bogus identities cannot simply join). The Ethereum identity chain is public, but identity contracts cannot be created or modified without Ministry approval, limiting the damage a 51% attack could do (an attacker could reorder or censor transactions on Ethereum but not forge a valid identity without the Ministry's key). Fabric's ordering service is operated by trusted parties, preventing any single entity from controlling the ledger history. We also implement TLS encryption for all network communications in the Fabric network to prevent eavesdropping or man-in-the-middle attacks between consortium nodes. * Data Confidentiality and Privacy: All personal data stored on the identity chain are encrypted with users' public keys, and DNA access tickets on-chain are encrypted, so even if the blockchain ledger is publicly accessible, the sensitive content remains unintelligible to unauthorized viewers. Off-chain DNA files are protected by hospital security measures and are only retrieved using access tickets that are issued via on-chain permission checks. If an adversary somehow obtains an access ticket without authorization, the ticket by itself is encrypted and time-limited, rendering it difficult to misuse. To further reduce exposure, our access tickets could be implemented as one-time tokens that are invalidated after use. Additionally, by not storing raw DNA sequences on-chain, we avoid the irreversible exposure of genomic data; if a data breach is detected off-chain, the data can be removed or its link updated, and the blockchain tickets can be revoked, an approach consistent with recommended privacy protection mechanisms [16]. * Integrating Institutional Security: Some security aspects fall outside the blockchain scope. For example, we assume hospitals properly secure their databases and that the governmental authorities managing the certificates remain uncompromised.