Tor the onion router

• 1. Tor The Onion Router Presented ByAshly Liza PhilipS5 MCARoll No. 06MACE

2. Privacy in public networks Internet is designed as a public network. Routing information is public. Encryption does not hide identities. Prone to traffic analysis 3. Contd..Internet data packetHeader DatapayloadSource,Whatever being sentdestination, timeEncryption cant Hidden by hideencryption 4. What is Anonymity? State of being not identifiable within a set ofsubjects. Unlink-ability of action and identity Unobserve-ability (hard to achieve) 5. Applications of Anonymity Privacy Untraceable electronic mail Law enforcement and intelligence Anonymous electronic voting Censorship-resistant publishing 6. Anonymous networks PipeNet Garlic Routing Onion Routing Anonymizer Crowds Java Anon Proxy 7. Onion Routing By David Goldschlag, Michael Reed, Paul Syverson ONION; special data structure. Uses public key cryptography Hides source and destination Anonymize TCP-based applications Protects anonymity of a user over network Resistant to eavesdropping and traffic analysis 8. Working of Onion Routing Uses an Onion Proxy Routes data randomly A router knows only its predecessor and successor No correspondence between data layers Different onion at each hop 9. RR4 R R R3 R1RR Alice R2 R Bob Sender chooses a random sequence of routers -Some routers are honest, some controlled by attacker -Sender controls the length of the path slide 9 10. Decrypting an Onion 11. Contd.. 12. Tor Implementation of Onion Routing TOR stands for The Onion Router. Second generation onion router. Low-latency anonymous network By Paul Syverson, Nick Mathewson, RogerDingledine in 2004 Maintained by Free Haven Project Hundreds of nodes on all continents 13. Contd.. Easy-to-use client proxy Freely available Supports only TCP Uses SOCKS interface No observer can tell where data comes from/going 14. Advancements over Onion RoutingPerfect forward secrecyVariable exit policiesDirectory serversLeaky-pipe circuit topologyEnd-to-end integrity checkingSOCKS interface 15. How Tor works? Same as Onion Routing Uses Diffie-Hellman key exchange Distributes data over several places Takes random pathway Used with Privoxy 16. Tor Circuit Each circuit shared by multiple TCP streams Circuit created preemptively Can recover from failure 17. Circuit setup Built from entry point one step at a timeCircuit ID is chosen randomly Diffie-Hellman process initiated Negotiate a symmetric session key Circuit extension and Relay packet 18. Tor Circuit setup(1)Client proxy establish a symmetric session key and circuit withOnion Router #1 19. Tor Circuit setup(2) Circuit extension 20. Tor Circuit setup(3)Client proxy extends the circuit by establishing a symmetricsession key with Onion Router #3 21. Using circuit 22. Cells in Tor Cell (512bytes) HeaderPayloadCircID Data Command 23. Contd.. Based on commands in cells:-Control cells Relay cellsCells 24. Commands in cells Control cells Relay Cells -padding - relay data -create/created -relay begin -destroy -relay end -relay connected -relay teardown -relay connected -relay extend/extended -relay truncate/truncated 25. E.g. Fetching a webpage 26. Congestion controlOR keeps track of PACKAGE WINDOW &DELIVERY WINDOW Window initialized to 1000cells Decremented accordingly Circuit throttling Forward nothing on reaching 0 Window initialized to 500cells Use relay sendme cells Stream throttling Incremented on receiving relaysendme 27. Hidden services Allow location hidden services Both end-points remain anonymous Both parties connect via a third party, the rendezvouspoint Introduction points act as contact points Server can be operated from inside a firewall 28. Creating and connecting to aLocation hidden service 29. Attacks on TorPassive attacksActive attacksAttacks against RendezvouspointsDirectory attacks 30. Users of TorLaw Militaries enforcement Bloggersofficers Journalists High profileActivistsand audience people NGOs 31. Weaknesses End-to-end Slow network Illegal use correlation 32. Real world deployment The Tor download page. 33. The Tor/Privoxy installer.Tor in the Windows system tray. 34. Setting up a proxy for Internet ExplorerThe Tor detector 35. Future enhancements Usability and Integration Scalability Caching at exit nodes 36. Conclusion Tor becomes most widely used anonymous networkwith its speed Tor supports mutual anonymity with the help ofRendezvous Point Tor resists local adversary effectively Tor anonymizes TCP streams, providing a high-throughput and low-latency network compared to theonion routing