In active traffic-analysis method, the attacker alters the timings of the packets of a flow according to a specific pattern and looks for that pattern on the other side of the network therefore, the attacker can link the flows in one side to the other side of the network and break the anonymity of it. In passive traffic-analysis method, the attacker extracts features from the traffic of a specific flow on one side of the network and looks for those features on the other side of the network. Traffic-analysis attack There are two methods of traffic-analysis attack, passive and active. In 2012, LASTor proposed a method to predict a set of potential ASes on these two segments and then avoid choosing this path during path selection algorithm on client side. Eavesdropping Autonomous system (AS) eavesdropping If an (AS) exists on both path segments from a client to entry relay and from exit relay to destination, such an AS can statistically correlate traffic on the entry and exit segments of the path and potentially infer the destination with which the client communicated. Researchers from the developed a network scanner allowing identification of 86% of live Tor 'bridges' with a single scan. However some protocols like and required a large amount of data before HTTP packets were identified.
Website fingerprinting yielded greater than 90% accuracy for identifying packets on conventional VPN protocols versus Tor which yielded only 2.96% accuracy. The reason for this is conventional single-hop protocols do not need to reconstruct packet data nearly as much as a multi-hop service like Tor or JonDonym. In spite of known weaknesses and attacks listed here, a 2009 study revealed Tor and the alternative network system (Java Anon Proxy, JAP) are considered more resilient to website fingerprinting techniques than other. Furthermore, to the recipient it appears that the last Tor (called the exit node), rather than the sender, is the originator of the communication. Because the of the sender and the recipient are not both in at any hop along the way, anyone eavesdropping at any point along the communication channel cannot directly identify both ends. Furthermore, by keeping some of the entry relays (bridge relays) secret, users can evade that relies upon blocking public Tor relays. That anonymity extends to the hosting of censorship-resistant content by Tor's anonymous hidden service feature. These onion routers employ in a multi-layered manner (hence the onion metaphor) to ensure between relays, thereby providing users with anonymity in network location. It is an implementation of, which encrypts and then randomly bounces communications through a network of relays run by volunteers around the globe. Tor aims to conceal its users' identities and their online activity from surveillance and traffic analysis by separating identification and routing.
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