# Securing Wireless Sensor Networks Using Machine Learning and Blockchain: A Review
## 10 BC-ML Integration
### Related Work  
Integrating the technologies of ML and BC to secure WSNs has been considered in the literature in several different directions, namely, secure routing, secure authentication, malicious nodes detection, and trust mechanism, as outlined in Table 4. \begin{table}
\begin{tabular}{c c c c} \hline \hline BC Type & Ref. & Security Threat & Study Highlights \\ \hline \multirow{4}{*}{[129]} & Injection, data tampering, firmware modification, listening to traffic & Proposes a new consensus algorithm model to reduce mining time. \\ \cline{2-4}  & \multirow{2}{*}{Routing attacks} & Utilizes BC as a shared memory for route determination to avoid untrusted nodes \\ \cline{2-4}  & & Relies on BC block technology to protect the flow routing tables at the nodes against routing attacks in an SDN-enabled WSN \\ \hline \multirow{4}{*}{[148]} & \multirow{2}{*}{Internal attacks} & Uses a subjective probability measure as a reputation level model for peer trust \\ \cline{2-4}  & & & \\ \cline{1-1} \cline{2-4}  & & & \\ \end{tabular}
\end{table} 
Table 3: Cont. \begin{table}
\begin{tabular}{l l l l l} \hline \hline \multicolumn{1}{l}{BC} & \multicolumn{1}{l}{ML} & \multicolumn{1}{l}{**Ref.**} & \multicolumn{1}{l}{**Attack**} & \multicolumn{1}{l}{**Study Highlights**} \\ \hline \multirow{8}{*}{Public} & \multirow{2}{*}{Deep CNN} & \multirow{2}{*}{[151]} & \multirow{2}{*}{Internal} & Trusted distributed routing using BC while avoiding routing paths with congestion and malicious nodes using DL-CNN \\  & & & & \\ \cline{2-5}  & Hidden Markov Model & [137] & Sybil & Trust model for identifying Sybil nodes; trust value is evaluated via HMM, and the trust values are then added to the BC \\ \cline{2-5}  & & & & \\ \cline{2-5}  & Histogram & & & BC-based authentication mechanism in which IPFS is integrated with BC for data storage, and HGB detection module to mitigate DoS attacks \\ \cline{2-5}  & & Isolated forest algorithm & [153] & Internal & Isolated forest algorithm for anomaly detection in the BC \\ \cline{2-5}  & Genetic Algorithm (GA)-based SVM and GA-based DT & [154] & Grayhole, mistreatment, and MITM & ML models for malicious node detection and registration along with authentication mechanism and data storage routing using BC \\ \hline \multirow{8}{*}{Consortium} & \multirow{2}{*}{RL} & \multirow{2}{*}{[155]} & \multirow{2}{*}{Blackhole} & Trusted routing with the use of BC and reinforcement learning \\  & & & & \\ \cline{2-5}  & DNN & & & \\ \cline{2-5}  & & & & \\ \cline{2-5}  & & & & \\ \hline \multirow{8}{*}{Hybrid} & \multirow{2}{*}{Gaussian NB} & \multirow{2}{*}{[122]} & \multirow{2}{*}{Internal} & BC-based identity management and secure authentication mechanism with Gaussian NB detection module to mitigate DoS attacks \\ \cline{2-5}  & & & & \\ \cline{2-5}  & & & & \\ \cline{2-5}  & & & & \\ \cline{2-5}  & & & & \\ \cline{2-5}  & & & & \\ \cline{2-5}  & & & & \\ \hline \multirow{8}{*}{N/A} & Generative Adversarial Networks (GAN) & [157] & Network layer & Authentication and validation of current routing data using a Generative Adversarial Network-based BC-enabled secured routing protocol \\ \cline{1-1} \cline{2-5}  & & & & \\ \cline{1-1} \cline{2-5}  & & & & \\ \cline{1-1} \cline{2-5}  & & & & \\ \cline{1-1} \cline{2-5}  & & & & \\ \cline{1-1} \cline{2-5}  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Existing research works on BC and ML integration for securing WSNs (N/A means not available). Securing WSN routing protocols using an integrated BC-ML approach has been considered in [151; 155; 156; 157]. The proposed framework in [155] relies on the BC network to securely record the routing information via the use of a registration contract, token contract, and token transactions, as well as to preserve data integrity by the use of PoA due to its high processing efficiency. The routing protocol of the proposed framework in [155] exploits a reinforcement learning algorithm to dynamically provide trusted routes.