Generally speaking, Tor aims to solve three privacy problems:įirst, Tor prevents websites and other services from learning your location, which they can use to build databases about your habits and interests. Similarly, servers in the Internet just see that they are being contacted by Tor nodes. Note that all your local ISP can observe now is that you are communicating with Tor nodes. More details on this process can be found in this visualization. Your communication is encrypted in multiple layers and routed via multiple hops through the Tor network to the final receiver. The aim of Tor is to improve your privacy by sending your traffic through a series of proxies. In addition, every server in the Internet that can see any of the packets can profile your behavior. In particular, your local ISP is in the position to build a complete profile of your Internet usage. Thus, every router between sender and receiver learns that the sender is communicating with the receiver. The way from sender to receiver involves multiple hops of routers, where each router inspects the destination IP address and forwards the packet closer to its destination. Internet communication is based on a store-and-forward model that can be understood in analogy to postal mail: Data is transmitted in blocks called IP datagrams or packets.Įvery packet includes a source IP address (of the sender) and a destination IP address (of the receiver), just as ordinary letters contain postal addresses of sender and receiver. Perhaps even run separate Tor clients for these applications. In most countries, the suspicion required to obtain a warrant already carries more weight than timing correlation would provide.įurthermore, since Tor reuses circuits for multiple TCP connections, it is possible to associate non anonymous and anonymous traffic at a given exit node, so be careful about what applications you run concurrently over Tor. In a more limited sense, note that if a censor or law enforcement agency has the ability to obtain specific observation of parts of the network, it is possible for them to verify a suspicion that you talk regularly to your friend by observing traffic at both ends and correlating the timing of only that traffic.Īgain, this is only useful to verify that parties already suspected of communicating with one another are doing so. Tor does not defend against such a threat model. As mentioned above, it is possible for an observer who can view both you and either the destination website or your Tor exit node to correlate timings of your traffic as it enters the Tor network and also as it exits.

Tor project success