## 2 Background
### Model Management
* Role-based access control: Participants are allocated distinct roles and permissions in accordance with their respective tasks inside the FLS. Implementing access controls guarantees that participants possess suitable levels of access, hence mitigating the risk of unauthorized activities and access to data. * Continuous authentication: The activities and behaviors of participants are continuously watched to identify any anomalies, ensuring that authenticated users maintain their authentication status. Including this feature enhances security measures by rapidly detecting and addressing any questionable behavior. * Symmetric encryption: In FLS, symmetric encryption plays a crucial role in maintaining data confidentiality and integrity. This method, utilizing the same key for both encryption and decryption, is particularly efficient for the large volumes of data typical in FLS. It ensures that sensitive information remains secure during transmission, as only model updates or insights are shared across the network, not the raw training data. This encryption method not only protects the data from potential eavesdroppers but also maintains their integrity, making any unauthorized alterations easily detectable. While symmetric encryption is central to preserving data privacy and consistency in FLS, it is typically complemented by other security measures, such as secure key management protocols, to provide a comprehensive security framework. The efficiency and effectiveness of symmetric encryption in these systems highlight its indispensability in the secure and efficient operation of FLS. The specific requirements of a particular FLS determine the most suitable authentication approach, taking into account aspects such as security, usability, scalability, and management complexity. These techniques can frequently be combined to achieve an efficient balance between security and usability. Table 4 provides a comparison of the main authentication mechanisms within FLSs. * Anonymous participants: When discussing FLSs, the term anonymous participants refers to the practice of protecting the participants' right to privacy and maintaining the confidentiality of their data and identities. Ensuring that users can participate in FLSs while maintaining anonymity is essential for protecting their data privacy. This objective is accomplished by using a variety of strategies and approaches. In FLSs, the following methods are frequently used by participants who wish to remain anonymous:
* Participant identity concealment: The concealment of participants' identities is a crucial measure in the FL process, as it guarantees the protection of their personal information from being disclosed. The preservation of user privacy fosters engagement from individuals and businesses who are apprehensive about the potential risks associated with data disclosure. * Data anonymization: In the context of FL, personal data undergo anonymization procedures prior to engagement, guaranteeing that even in the event of unauthorized access, the data cannot be directly associated with identifiable individuals. Methods such as differential privacy, k-anonymity, and data perturbation can be employed to achieve data anonymization
* Pseudonymization: During the FL process, participants are not required to reveal their true identities and instead employ pseudonyms or temporary IDs. The utilization of this technology affords a level of anonymity, making it more challenging to trace particular data contributions to specific individuals. * Blockchain-based identity management: The utilization of blockchain technology facilitates the management of participants' identities and transactions in a decentralized and tamper-proof manner. The elimination of a central authority and the provision of transparent and safe identity management contribute to the enhancement of security and privacy. The emphasis on preserving participant anonymity is pivotal for building trust, encouraging engagement, and safeguarding privacy within FLSs.