# TOAR: Toward Resisting AS-Level Adversary Correlation Attacks Optimal Anonymous Routing
## 7 Related Works  
Research work related to this paper includes anonymous communication routing algorithms, inter-domain routing, and software-defined networks.  
By manipulating the underlying routing, AS-level adversaries increase their chances of executing correlation attacks, leading to the proposal of various AS-aware path selection schemes for Tor [9; 10; 24; 25; 26]. [PERSON] provided the first work [14] considering attacks from the perspective of an AS-level adversary. To counter the risk of AS-level adversary attacks, LASTor [24] modifies the Tor routing algorithm and designs and implements a new Tor client, which achieves probabilistic path selection by predicting Internet routes between onion nodes and end hosts to avoid ASes that may be subjected to an attack at the AS level. Counter-RAPTOR [12] proposed the Tor guard node selection algorithm and designed two monitoring frameworks for monitoring BGP to detect control plane attacks and monitoring trace routes to detect data plane anomalies in order to minimize and detect AS-level routing attacks. However, overlay AS-aware path selection schemes provide partial routing information to infer the underlying network path between two endpoints on the Internet. The most direct method for detecting the ASs at both ends of a Tor connection is to use tools similar to traceroute to analyze the network path from the client to the selected entry node and from the exit node to the destination. These inferences may be inaccurate.  
SDN is a promising way to re-architect the Internet, and the transition from traditional networks to SDN is an important issue. RouteFlow [27] is one of the earliest methods to implement IP routing on OpenFlow switches. Another BGP-based solution is SDN-IP [28], which focuses on solving the problem of seamless interconnection between SDN domains and traditional domains. Some new routing protocols [19; 29; 30; 31; 32; 33] have been proposed to address the Internet routing scalability and source-controlled routing to provide flexible end-to-end routing schemes, but do not focus on identity privacy in communication.  
Some new network-level high-speed anonymous systems [20; 23; 34; 35; 36; 37; 38; 39] have been proposed, but have not focused on routing computations. These studies inspire us to tackle the problem of anonymity degradation in Tor by AS adversary association attacks, focusing on AS routing in SDN networks. However, these studies assume that inter-domain shortcuts provided by the underlying network architecture already exist and adequately address routing computation issues. Both from the viewpoint of network-layer anonymous  
Figure 13: Throughput of route forwarding.  
communication and in supporting the overlay anonymous such as Tor in AS-aware relay node selection, there are inherent challenges in routing computation.  
This paper takes a different approach than overlay solutions by proposing a method focused on end-to-end routing control within an SDN architecture. It aims to identify inter-domain routing paths that balance performance--specifically, the speed of low-latency anonymous communication--and security, represented by the probability of paths being compromised by adversaries. Differing from existing SDN-based network-layer anonymity solutions, this paper extends anonymous communication from intra-domain control to inter-domain control within SDN networks, ultimately supporting anonymity as a service for users on a broader scale.