## 5 Fuzzy Logic Approaches in Trust Management
### Effective Metrics and Comparative Analysis of Methods Based on These Metrics
#### 5.2.1 Comparative Analysis Based on Metrics
The research study in [40] examined various factors crucial to evaluating trust, such as availability, privacy, scalability, integrity, and dynamicity:  
* Scalability: The scheme incorporates a lazy update and dynamic storage structures to support the mobility of on-board units (OBUs), which can enhance scalability by reducing the computational overhead for road-side units (RSUs). * Integrity: By utilizing fuzzy theory and behavioral big data for trust evaluation, the scheme aims to ensure the integrity of the trustworthiness assessment in VANETs, enhancing the reliability of communication and message authenticity. * Availability: The mutual authentication process and incentive mechanisms in the scheme contribute to ensuring the availability of trust evaluation services in VANETs and promoting continuous and reliable communication among participants. * Privacy: The scheme provides mutual authentication with conditional anonymity between the RSU and OBU, protecting the privacy of participants while maintaining traceability in the case of disputes, thus addressing privacy concerns in trust evaluation. * Dynamicity: The scheme considers the mobility of vehicles in VANETs and incorporates mechanisms such as lazy updates and dynamic storage structures to adapt to the dynamic nature of the network, enhancing the system's ability to handle changes and updates efficiently. Several important variables in assessing trust were covered in the article in [46], including context awareness, scalability, integrity, availability, privacy, and dynamicity. * Scalability: TrustBlock's use of a double-layer blockchain architecture and adaptive historical trust weight demonstrates considerations for scalability by providing a framework for managing trust values at the network scale. * Integrity: The use of blockchain technology in TrustBlock ensures the integrity of the trust data, providing tamper-proof and irrefutable storage of trust values, which contributes to maintaining the integrity of the trust evaluation process. * Availability: TrustBlock's approach to trust evaluation, utilizing blockchain for secure and effective trust value storage and sharing, contributes to ensuring the availability of trust-related information in SDN. * Privacy: While this article primarily focuses on trust evaluation and security aspects, the use of blockchain technology in TrustBlock can potentially contribute to privacy preservation through secure and authenticated data storage and sharing. * Dynamicity: TrustBlock's adaptive historical trust weight and comprehensive evaluation model reflect considerations for dynamic trust assessment, allowing for the adjustment of trust values over time based on node behavior and interactions. * Context Awareness: The trust evaluation model in TrustBlock considers the context of node interactions and behaviors, incorporating direct, indirect, and historical trust perspectives to provide a comprehensive assessment of node trustworthiness within the context of SDN networks. Scalability, integrity, availability, privacy, and dynamicity are critical factors in evaluating trust and were included in the study [47]:
* Scalability: Although the scalability aspect is not explicitly mentioned in the provided excerpts, the use of fuzzy trust calculations and the consideration of online and offline information suggest a scalable approach to managing trust and privacy in a network with a large number of users. * Integrity: The Trust2 Privacy mechanism focuses on preserving the integrity of users' information by allowing them to set privacy levels and encrypt sensitive data according to their preferences. This approach ensures that users have control over the integrity of their personal information even after it is shared on social platforms. * Availability: Using cryptographic tools to protect different levels of sensitive information, the mechanism aims to balance privacy preservation with the availability of information for users. * Privacy: Privacy preservation is a central aspect of the Trust2 Privacy mechanism.