# Blockchain Solutions for Enhancing Security and Privacy in Industrial IoT
## 3 Background
### Industrial Internet of Things (IIoT)  
The Industrial Internet of Things (IIoT) [19,25] refers to a network of interconnected devices, sensors, and systems deployed in various industrial settings, including manufacturing, energy, logistics, and critical infrastructure. These components interact in real time, enabling automation, predictive maintenance, and process optimization. The primary technical goal of the Industrial Internet of Things (IIoT) is to enhance operational efficiency, improve decision making, and minimize downtime through continuous data exchange and integration.  
In practice, the IIoT enables advanced capabilities such as real-time monitoring, data analytics, and machine learning. For instance, the IIoT integrates automated machines, sensors, and cloud-based platforms to facilitate smart factory operations in manufacturing environments. These systems can oversee production lines, monitor inventory, predict maintenance needs, and optimize workflows to enhance efficiency. The architecture of such systems typically involves edge computing for immediate data processing, cloud services for storage and advanced analysis, and communication protocols like MQTT (Message Queuing Telemetry Transport) or OPC-UA (Open Platform Communications Unified Architecture) to ensure seamless connectivity between devices [11].  
To support the adoption of the Industrial Internet of Things (IIoT), the Industrial Internet Consortium (IIC) developed the Industrial Internet Reference Architecture (IIRA) [12], based on the ISO/IEC/IEEE 42010:2011 standard. The IIRA provides a comprehensive framework for system design, categorizing IIoT systems into four primary viewpoints: business, use, functional, and implementation. Each viewpoint offers guidance on the various aspects of system architecture, including defining business objectives, outlining functional requirements, and detailing implementation steps for hardware, software, and network infrastructure.  
While the IIRA offers a scalable and adaptable framework, it does not provide specific technical details about individual technologies or protocols. To address this limitation, South Korea's Smart Factory Promotion Team introduced a smart factory reference model, which focuses on industry-specific requirements for smart factory systems [25,26]. This model defines the key terms and operational conditions of smart factories, presenting a layered approach that covers all phases of the manufacturing process--from order placement to production and shipment. Although the smart factory model does not delve deeply into technical implementations, it outlines the necessary automation and control systemsat various stages of the factory lifecycle, ranging from field automation to application system integration. Figure 1 illustrates the IIRA, smart factory reference models, and major cyberattacks targeting each architecture layer.  
As IIoT systems generate vast amounts of data, their architecture must ensure smooth and secure data flow across interconnected devices. However, the growing number of connected devices also expands the potential attack surface for cybersecurity threats. Each device represents an additional entry point for cyberattacks, making IIoT systems increasingly vulnerable to unauthorized access, data breaches, and operational disruptions. A PwC (PricewaterhouseCoopers) survey [6] revealed that 59% of organizations struggle to secure IoT devices, with vulnerabilities often stemming from legacy systems and inadequate security practices. These cybersecurity threats underscore the urgent need for robust cybersecurity frameworks to safeguard industrial data and maintain continuous operations, as even a single compromised component can result in widespread system failures.