# Blockchain Solutions for Enhancing Security and Privacy in Industrial IoT
## 4 Blockchain-Based Architecture and System Design
### System Entities and Interactions
Implemented using time series databases like InfluxDB, data is hashed using algorithms such as SHA-256 before storage, with each hash linked to its corresponding blockchain transactions. Access control mechanisms based on token authentication, such as JSON Web Token (JWT), enforce strict user permissions. To enhance availability and fault tolerance, the database is replicated across multiple trusted nodes, ensuring continuity even in the face of hardware failures or network disruptions. This component bridges the gap between operational technology (OT) and information technology (IT), enabling seamless integration with enterprise-level analytics tools and dashboards used for strategic decision making. The blockchain layer provides the foundation for decentralized trust, immutability, and tamper-proof logging of all system transactions. It plays a central role in secure identity management, creating audit trails, and executing smart contracts. Built on permissioned blockchain platforms like Ethereum, utilizing Proof-of-Stake (PoS) consensus, this layer stores the cryptographic hashes of sensor data, timestamps, and device identifiers rather than raw data, thereby preserving privacy and scalability. Smart contracts written in Solidity enforce the rules governing data access, device registration, and mitigation strategies for cyber threats such as DDoS attacks. Nodes within the blockchain layer are categorized into miners, transaction nodes, and light nodes, depending on their computational capabilities and assigned roles within the network. By leveraging the immutability of blockchain records, the system ensures the complete traceability of events, which is essential for forensic analysis, compliance reporting, and audit purposes. The end users represent the human operators or enterprise applications that interact with the system to retrieve data, monitor performance, and make informed decisions. These users access the system through web dashboards developed using modern front-end frameworks such as Vue.js. Through REST APIs exposed by the controller module, they query data from the database or blockchain, enabling real-time visibility into system operations. Authentication is enforced using multi-factor methods or biometric verification to prevent unauthorized access. The users receive alerts and notifications via email and push notifications triggered by predefined thresholds or anomalies detected through deep learning models analyzing network behavior. The design of user interfaces emphasizes real-time insights and historical trend analysis, supporting data-driven decision making and rapid response to system events. To address the high transaction throughput requirements of IIoT environments, the proposed system leverages edge computing to boost the processing capacity for blockchain mining tasks. By utilizing edge computing resources, the system can efficiently handle large transactions without compromising integrity or real-time performance. This approach ensures network security, device identity management, and safe, transparent data exchanges. Figure 4 illustrates the interaction and data flow across various components of the blockchain-integrated IIoT system architecture. The data flow begins with IoT devices collecting and transmitting encrypted data to secure hubs. These hubs forward the data to edge computing nodes, which perform preprocessing, filtering, and authentication. The validated data is then sent to the controllers, which manage the data flow, enforce security policies, and write transactions to the blockchain. The blockchain records all transactions, ensuring traceability and accountability. Finally, the end users interact with the system to access and analyze the validated data stored in the database. Each entity within the system performs a distinct and technologically defined role, contributing to the overall efficiency, scalability, and security of the blockchain-enhanced Industrial Internet of Things (IIoT) architecture.