Given the visibility of the tunnel creation phase within tunnel-based anonymity structures, an entity’s traffic can be segregated based on the relay selection mechanism employed. Hence, the global attacker’s capability to detect communications and undermine the anonymity of entities is heightened. Another factor that can aid the attacker in identifying the tunnels is the improper combination of created tunnels and variations in the positioning of a combined relay within those tunnels. One potential solution to address these issues is to combine tunnels traffic by restricting the list of selectable relays. This can be accomplished by taking into account the choices made by tunnel owners and the network structure, as well as ensuring that the common selected relays occupy the same positions within the tunnels. We propose a clustering structure with routing capabilities to establish an infrastructure for creating combined tunnels. Our method has two key pillars. Firstly, both the tunnel creation packets and data packets follow the same pattern, making it difficult for the attacker to differentiate tunnel creation traffic from regular network traffic. Secondly, by allowing entities to join different clusters and maintaining a high ratio of entities to the number of interfaces within each cluster, the probability of combining traffic from senders within the same cluster is significantly increased. These interfaces within the proposed structure are referred to as permanent relays. Given the hierarchical nature of the proposed structure, the positions of relays within the tunnels of a cluster remain consistent. To assess the effectiveness of the proposed structure, we employ the average degree of anonymity metric, which relies on the Shannon entropy concept. Simulation results demonstrate a substantial increase in the degree of anonymity achieved by the proposed structure in comparison to previous approaches.
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