Onion routing and tor: Fundamentals and Anonymity
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Onion Routing and Tor: Fundamentals and anonymity discusses anonymity on the internet and how Tor works to provide anonymity. It explains that traditional IP addresses and browser tracking can be linked to a user's identity. Tor creates circuits through multiple relay nodes to hide a user's location and communications. Key features of Tor include using volunteer-run relay nodes, protecting against traffic analysis, and enabling hidden services to host anonymous websites. While Tor enhances anonymity, it cannot prevent all timing attacks if the start and end of a user's traffic can be observed.
Onion routing and tor: Fundamentals and Anonymity
- 1. Onion Routing and Tor: Fundamentals and anonymity Anurag Singh
- 3. What is Anonymity ? Anonymity is the state of being unidentifiable within a set of subjects. ◦ Hide your activities among others’ similar activities ◦ You cannot be anonymous by yourself! Unlinkability of action and identity Unobservability (hard to achieve) Observer cannot even tell whether a certain action took place or not
- 4. You Are Not Anonymous Your IP address can be linked directly to you ◦ ISPs store communications records ◦ Usually for several years (Data Retention Laws) ◦ Law enforcement can subpoena these records Your browser is being tracked ◦ Cookies, Flash cookies, E-Tags, HTML5 Storage ◦ Browser fingerprinting Your activities can be used to identify
- 5. Who Uses Anonymity Systems ? “If you’re not doing anything wrong, you shouldn’t have anything to hide.” • Implies that anonymous communication is for criminals The truth: who uses Tor? • Journalists • Business executives • Law enforcement • Military/intelligence • Human rights activists personnel • Normal people • Abuse victims Fact: Tor was/is developed by the Navy
- 6. Why Do We Need Anonymity ? To protect privacy ◦ Avoid tracking by advertising companies ◦ Viewing sensitive content Information on medical conditions Advice on bankruptcy Protection from prosecution ◦ Not every country guarantees free speech To prevent chilling-effects ◦ It’s easier to voice unpopular or controversial opinions if you are anonymous
- 7. Anonymity Layer Function: ◦ Hide the source, destination, and content of Internet flows from eavesdroppers Key challenge: ◦ Defining and quantifying anonymity ◦ Building systems that are resilient to deanonymization ◦ Maintaining performance Applicatio n Anonymity Presentatio Sesnsion Transport Network Data Link Physical
- 8. Related Work Chaum’s Mix-Net design ◦ Correspondence hiding between sender & receiver by wrapping messages in layers and relaying through “mix” routers. Babel ‘s Mix master and Mixminion ◦ Try to maximize anonymity at the cost of high latency. Anonymizer ◦ Single-hop proxy PipeNet ◦ Low-latency design giving user anonymity by shutting down the network by not sending.
- 9. Related Work P2P Tarzan and MorphMix designs ◦ Rely and generate traffic for other participating users and hide who originated or relayed a request. Hordes/Crowds ◦ Hides the initiator of traffic thorough multicast responses Freedom ◦ Supports session keys and address of the server in a circuit. Rennhard’s Anonymity Network ◦ Builds circuits in stages which helps to obtain perfect forward secrecy by extending them one hop at a time.
- 10. Threats to Anonymity Traffic Analysis ◦ Passive traffic analysis Infer from network traffic who is talking to whom To hide your traffic, must carry other people’s traffic! ◦ Active traffic analysis Inject packets or put a timing signature on packet flow. Compromised network nodes (routers) ◦ It is not obvious which nodes have been compromised Attacker may be passively logging traffic ◦ Better not to trust any individual node Assume that some fraction of nodes is good, don’t know which
- 11. How Traffic Analysis Work ? Internet data packets have two parts: ◦ a data payload Generally Encrypted traffic analysis still reveals a great deal about what you're doing and, possibly, what you're saying. because ◦ a header used for routing it focuses on the header, which discloses source, destination, size, timing, and so on. simple traffic analysis ◦ sitting somewhere between sender and recipient on the network, looking at headers. sophisticated traffic analysis Encryption does not help against these attackers, since it only hides the content of Internet traffic, not the headers.
- 12. Onion Routing (Original) A technique for anonymous communication over a computer network. Messages are repeatedly encrypted and then sent through several network nodes called onion routers. Like someone peeling an onion,each onion router removes a layer of encryption to uncover routing instructions, and sends the message to the next router where this is repeated. This prevents these intermediary nodes from knowing the origin, destination, and contents of the message.
- 13. Onion Router and Analogy
- 14. Tor (The Second Generation Onion Router) a distributed, anonymous network reduce the risks of both simple and sophisticated traffic analysis by distributing transactions over several places on the Internet. data packets on the Tor network take a random pathway through several relays. no observer at any single point can tell where the data came from or where it's going.
- 15. Tor (The Second Generation Onion Router) Basic design: a mix network with improvements ◦ Perfect forward secrecy ◦ Introduces guards to improve source anonymity ◦ Takes bandwidth into account when selecting relays Mixes in Tor are called relays ◦ Introduces hidden services Servers that are only accessible via the Tor overlay
- 16. Deployment and Statistics Largest, most well deployed anonymity preserving service on the Internet ◦ Publicly available since 2002 ◦ Continues to be developed and improved Currently, ~5000 Tor relays around the world ◦ All relays are run by volunteers ◦ It is suspected that some are controlled by intelligence agencies 500K – 900K daily users ◦ Numbers are likely larger now, thanks to Snowden
- 17. How Tor Works ? Courtesy: https://www.torproject.org/about/overview.html.en
- 18. How Tor Works ?...Circuit Setup Courtesy: https://www.torproject.org/about/overview.html.en
- 19. How Tor Works ?....new connection Courtesy: https://www.torproject.org/about/overview.html.en
- 20. Tor Enhancements over Previous Onion Routing applications Tor uses telescoping path-built design ◦ Previous designs allowed hostiles to record traffic and compromise successive nodes. Tor uses SOCKS proxy interface ◦ Previous designs required a separate application proxy for each application protocol. Tor is able to share one circuit for many TCP streams ◦ Previous designs required a separate circuit for each application level request. Which is a threat to anonymity. Leaky pipe circuit topology
- 21. Tor Enhancements over Previous Onion Routing applications Directory servers ◦ Previous designs resorted to flooding info on the network. Variable exit policies End-to-end integrity checks ◦ Previous designs had no integrity checks. Rendezvous points/hidden services ◦ Previous designs included replay onions. Congestion control: uses end-to-end acks ◦ Previous designs didn’t address traffic bottlenecks.
- 22. Hidden Services Tor is very good at hiding the source of traffic ◦ But the destination is often an exposed website What if we want to run an anonymous service? ◦ i.e. a website, where nobody knows the IP address? Tor supports Hidden Services ◦ Allows you to run a server and have people connect ◦ … without disclosing the IP or DNS name Many hidden services ◦ Tor Mail, Tor Char ◦ DuckDuckGo ◦ Wikileaks • The Pirate Bay • Silk Road (2.0)
- 23. Hidden Services Example: Creating a hidden Server Server creates circuits to “introduction points” Server gives intro points’ descriptors and addresses to service lookup directory Client obtains service descriptor and intro point address from directory
- 24. Using a Location Hidden Service Client sends address of the rendezvous point and any authorization, if needed, to server through intro point If server chooses to talk to client, connect to rendezvous point If server chooses to talk to client, connect to rendezvous point Client creates a circuit to a “rendezvous point”
- 25. Staying Anonymous Tor can't solve all anonymity problems. It focuses only on protecting the transport of data to protect your anonymity, be smart. Tor does not provide protection against end-to-end timing attacks: ◦ If your attacker can watch the traffic coming out of your computer, and also the traffic arriving at your chosen destination, he can use statistical analysis to discover that they are part of the same circuit.
- 26. The Future of Tor Providing a usable anonymizing network on the Internet today is an ongoing challenge. Recent activities like NSA snooping. More number of users attracted towards Tor. Each new user and relay provides additional diversity, enhancing Tor's ability to put control over your security and privacy back into your hands.
- 27. THANKYOU