# Towards Tamper-Proof Trust Evaluation of Internet of Things Nodes Leveraging IOTA Ledger
## 1 Introduction
In contrast, decentralized trust evaluation approaches eliminate reliance on a single authority by distributing trust computation and decision-making across participating nodes. This distribution enhances system resilience, improves scalability, and better preserves privacy. Decentralized models are inherently more robust against targeted attacks, such as trust manipulation or data interception, as trust is derived from local observations and peer consensus. However, they introduce challenges related to synchronization, latency, and the need for efficient consensus protocols [16]. Despite these trade-offs, the comparative advantages of decentralization, particularly in terms of fault tolerance and data integrity, underscore the urgent need for a paradigm shift toward decentralized and tamper-resistant trust evaluation frameworks tailored to the dynamic nature of IoT environments. A key requirement for any decentralized trust evaluation framework is the prevention of fraudulent trust scores [19]. In a decentralized system, it is crucial that no node manipulates its own trust score or the scores of other nodes to present a fake trust value. This ensures the reliability and integrity of the trust evaluation process. Leveraging distributed ledger technologies, such as IOTA, can address this challenge by providing a secure and immutable record of trust scores [20]. Each transaction is cryptographically secured and recorded on the ledger, making it tamper-proof. This immutability ensures that once a trust score is assigned, it cannot be altered or forged by any node to maintain the authenticity of the trust evaluation process. Such a robust mechanism is essential for building a secure and trustworthy IoT ecosystem, where each node's behavior can be accurately assessed and monitored. To address these pressing concerns, this paper proposes a novel approach to trust evaluation within IoT networks, aimed at mitigating the vulnerabilities inherent in centralized architectures. Our approach decentralizes the trust assessment process, distributing the responsibility of trust evaluation across multiple nodes. Central to our approach is the development of mechanisms to ensure the integrity and confidentiality of sensitive trust data stored on IoT nodes. We leverage IOTA Tangle to create an immutable and secure repository for trust scores to ensure that once trust data are recorded, they cannot be tampered with or altered by malicious actors. This cryptographic security fortifies the overall security posture of the system, as trust scores remain authentic and reliable. Additionally, by decentralizing the storage and management of trust data, the proposed scheme minimizes the risk of privacy breaches. Each node contributes to the trust evaluation process without needing to disclose sensitive information to a central authority, thereby preserving the privacy of individual nodes and preventing a single point of failure. The proposed framework also incorporates both direct and indirect trust metrics, providing a comprehensive and nuanced assessment of each node's trustworthiness. Direct metrics include the node's own behavior and historical performance, while indirect metrics are derived from feedback and interactions with other nodes in the network. In addition, the framework introduces a third dimension: IOTA-based behavioral metrics, including Transaction Confirmation Rate (TCR), Reattachment Frequency (RF), Cumulative Weight Contribution (CWC), and Cumulative Transaction Contribution (CTC). By integrating these diverse metrics, we achieve a more accurate and holistic evaluation of trust, enhancing the network's ability to detect and isolate malicious or unreliable nodes. This multi-faceted approach not only strengthens security but also ensures the system's robustness and reliability. This paper contributes the following:  
* Development of a decentralized trust evaluation framework utilizing IOTA technology to mitigate risks associated with centralized trust evaluation methods, such as single points of failure and privacy breaches.