# TrustShare: Secure and Trusted Blockchain Framework for Threat Intelligence Sharing
## 5 Security Analysis
### Threat Mitigation  
TrustShare uses a defense-in-depth approach, incorporating Ciphertext-Policy Attribute-Based Encryption (CP-ABE), Hyperledger Fabric's permissioned blockchain, and X.509 certificate-based identity management. These controls are implemented across the TrustShare workflow, as shown in Table 10.  
Below is a brief explanation of how each mitigation aligns with specific threats: \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Threat** & **Description** & **Mitigation Strategy** & **Enforced in Process** \\  & & & **Step(s)** \\ \hline \multirow{3}{*}{Sybil Attack} & \multirow{3}{*}{Adversary creates fake identities to subvert the system.} & Identity validation via MSP and CA-issued & \multirow{3}{*}{Pre-Step 1; Step 7} \\  & & X.509 certificates; verified at user & \\  & & registration (pre-Step 1) and & \\  & & transaction submission. & \\ \hline \multirow{3}{*}{Chaincode Poisoning} & \multirow{3}{*}{Injection of malicious or unauthorized chaincode.} & Multi-peer endorsement policies for & \multirow{3}{*}{Step 8} \\  & & chaincode invocation; secure CI/CD & \\  & & pipeline with version control and & \\ \cline{1-1}  & & audit logs. & \\ \hline \multirow{3}{*}{Identity Spoofing} & \multirow{3}{*}{Inpersonation of authorized users or nodes.} & Mutual TLS authentication and certificate & \multirow{3}{*}{Steps 10–12} \\  & & validation enforced during access and & \\  & & data retrieval. & \\ \hline \multirow{3}{*}{Replay Attack} & \multirow{3}{*}{Reuse of previously valid or fraudulent transactions.} & Hyperledger Fabric-native timestamps and & \multirow{3}{*}{Steps 7–9} \\  & & cryptographic nonces validated by & \\ \cline{1-1}  & & ordering service and peers. & \\ \hline \multirow{3}{*}{\begin{tabular}{c} Insider \\ Threats/Credential \\ Misuse \\ \end{tabular} } & \multirow{3}{*}{Malicious actions by legitimate users or credential compromise.} & CP-ABE encryption for fine-grained access & \multirow{3}{*}{Steps 4, 9, 12, and 15} \\  & & control; immutable blockchain audit trails & \\ \cline{1-1}  & & for accountability. & \\ \hline \multirow{3}{*}{Anomalous Behavior} & \multirow{3}{*}{\
\begin{tabular}{c} Suspicious or abnormal access \\ patterns indicating compromise. \\ \end{tabular} } &
\begin{tabular}{c} Planned SIEM integration for real-time \\ monitoring; rule-based and ML anomaly \\ detection on logs. \\ \end{tabular} & \multirow{3}{*}{Steps 1–3, 12–15} \\  & & detection of logs. & \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Threat mitigation mapping across TrustShare process steps. **Sybil Attacks (Pre-Step 1; Step 7):** Only identities validated via Hyperledger Fabric's MSP and trusted certificate authorities are allowed to register and submit transactions. 2. **Chaincode Poisoning (Step 8):** Chaincode deployment requires multi-peer endorsements and is secured through a CI/CD pipeline with auditing and version control. 3. **Identity Spoofing (Steps 10-12):** TrustShare uses mutual TLS to ensure endpoint authenticity during data access and retrieval. 4. **Replay Attacks (Steps 7-9):** Hyperledger Fabric-native timestamps and cryptographic nonces ensure message freshness, mitigating replay attempts. 5. **Insider Threats and Credential Misuse (Steps 4, 9, 12, and 15):** CP-AB enforces encryption-time access control, while blockchain audit logs provide tamper-evident traces. 6. **Anomalous Behavior (Steps 1-3, 12-15):** Planned integration with SIEM tools such as the ELK Stack and Splunk will support anomaly detection using rule-based and machine learning methods. _Future Work:_ While CP-AB enforces robust encryption under the Decisional Bilinear Diffie-Hellman (DBDH) assumption, future work will investigate post-quantum cryptographic alternatives to safeguard long-term confidentiality. SIEM integration will also be operationalized in the production release. This layered architecture, aligned with operational checkpoints and enforced at the protocol level, ensures TrustShare's resilience against common and advanced threat vectors while maintaining compliance and auditability.