## 10 Blockchain
Through cryptographic techniques and consensus algorithms, a blockchain can verify the origin and validity of data, preventing tampering or unauthorized modification. * Secured identity management: Blockchain technology provides a robust framework for managing digital identities securely. Individuals and devices can verify and store their identities on a blockchain, ensuring that only authorized entities can access sensitive information or perform specific actions. * Enhanced IoT security: IoT devices, an integral part of smart cities, can introduce security vulnerabilities. A blockchain can establish a decentralized and secure network for IoT devices, eliminating the need for a central point of control and reducing the risk of cyberattacks. * Peer-to-peer transactions: A blockchain's inherent capabilities allow secure peer-to-peer transactions without intermediaries. This eliminates the need for trust in centralized authorities. * Data consent: Various stakeholders need access to specific data in a smart city ecosystem. Blockchain-based solutions can enable controlled data sharing with the use of smart contracts. Individuals or organizations can grant permission for data access, ensuring privacy while fostering collaboration. When deploying blockchain technology in smart cities, several challenges may arise. Addressing these challenges requires collaboration between technology providers, city governments, regulatory bodies, and the community. Table 16 presents the main challenges of deploying a blockchain for smart cities [114; 115; 116]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Challenge** & **Discussion** \\ \hline \multirow{3}{*}{Scalability} & Blockchain networks often face scalability challenges when dealing with many transactions and data, which may pose difficulties when trying to handle the scale and complexity of a smart city. \\ \cline{1-1}  & \\ \cline{1-1}  & \\ \cline{1-1}  & \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Challenges of deploying blockchain for smart cities. \begin{table}
\begin{tabular}{c c} \hline \hline
**Benefit** & **Blockchain-Based Smart City** \\ \hline \multirow{4}{*}{Citizen engagement and governance} & A blockchain can give citizens more control over their data, giving them transparency, privacy, and the ability to participate in decision-making. A blockchain can enable secure and transparent voting systems, ensuring integrity in the democratic processes within a smart city. It can also facilitate decentralized identity systems, allowing citizens to control their data while ensuring privacy and security. \\ \hline \multirow{3}{*}{Data sharing and interoperability} & A blockchain facilitates secure and decentralized data sharing between various stakeholders within a smart city ecosystem. It can promote interoperability and collaboration between different service providers and government agencies. \\ \cline{1-1}  & Adopting blockchain technology can attract investments, foster entrepreneur, and promote innovation within a smart city ecosystem. It can create new economic opportunities, attract tech startups, and enable the development of decentralized applications that cater to specific urban needs.