# Cybersecurity for Blockchain-Based IoT Systems: A Review
## 5 Discussion
### IoT Security and Blockchain  
The poor design and maintenance of IoT devices make them susceptible to malware attacks that can result in data theft, device hijacking, or operational disruptions. Furthermore, IoT devices often being situated in remote or unsecured locations makes them vulnerable to physical attacks, including theft, damage, or operational interference [37; 38]. As illustrated in Figure 5, IoT systems are vulnerable to several security threats, including:  
* Data breaches: IoT devices often collect and store sensitive data, such as user personal information, location data, and financial data. If these data are compromised, they could be used for identity theft, fraud, or other malicious activities. * Malware attacks: IoT devices are often poorly designed and maintained, making them vulnerable to malware attacks. Malware could be used to steal data, take control of devices, or disrupt operations. Figure 4: The Integration of IoT Devices with blockchain. * Physical attacks: IoT devices are often located in remote or unsecured locations, making them vulnerable to physical attacks. Attackers could steal or damage devices, or disrupt their operations. Blockchain technology offers multiple avenues to bolster the security of IoT systems. Firstly, through encryption, blockchain can safeguard the data stored on IoT devices by rendering it indecipherable to unauthorized individuals. Moreover, blockchain enables authentication mechanisms that verify the identities of users and devices, guaranteeing that only authorized entities gain access to the system. Access control is another vital aspect facilitated by blockchain, permitting precise control over data and device accessibility, thereby limiting potential risks [17; 38]. Additionally, blockchain's vulnerability management capabilities aid in identifying and addressing vulnerabilities within IoT systems, reducing their susceptibility to attacks. Furthermore, incorporating explainable artificial intelligence (XAI) techniques within blockchain-based IoT systems can provide additional benefits [39]. Based on our analysis, we find that blockchain technology can be used to improve the security of IoT systems in a number of ways:  
* Encryption: Blockchain can be used to encrypt data stored on IoT devices, making it more difficult for unauthorized users to access. * Authentication: Blockchain can be used to authenticate users and devices, ensuring that only authorized users have access to the system. * Access control: Blockchain can be used to control who has access to data and devices, and what they can do with it. * Vulnerability management: Blockchain can be used to identify and mitigate vulnerabilities in IoT systems, making them less susceptible to attack. * XAI: XAI techniques aim to explain the inner workings, decisions, and outcomes of complex AI systems in an interpretable and transparent manner. This is particularly valuable for blockchain-based IoT systems due to several reasons [40]:  
Figure 5: Vulnerabilities and Risks Associated with IoT Systems. * Enhancing accountability: By understanding how blockchain decisions are made, stakeholders can ensure the system is functioning correctly and accountable for its actions. This builds user trust. * Debugging issues: Interpretable explanations of the blockchain's behavior can help debug any issues within the system and identify potential vulnerabilities. * Adapting to changes: Explanations provide insight into how the system is performing, which can guide necessary changes and updates over time. * Deterring attacks: Increased transparency into the blockchain network's operations can act as a deterrent against potential attackers by making exploitation more difficult. Furthermore, we review some XAI techniques that could be applied to blockchain-based IoT systems [41; 42] including:  
* Model summarization: This technique condenses complex models into simpler, interpretable representations. This can be done by using natural language descriptions, decision trees, or other techniques.