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Scalable Onion Routing with Torsk

Scalable Onion Routing with Torsk. Presented by Huabo Lu. Images of Torsk. For v isual learning, here is how Torsk looks like:. Scalable Onion Routing with Torsk. Onion Routing Tor Scalable Onion Routing Tor would not scale.

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Scalable Onion Routing with Torsk

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  1. Scalable Onion Routing with Torsk Presented by Huabo Lu

  2. Images of Torsk For visual learning, here is how Torsk looks like:

  3. Scalable Onion Routing with Torsk • Onion Routing • Tor • Scalable Onion Routing • Tor would not scale. • Scale is important: large number of users is a must for anonymity. • Torsk: P2P & DHT lookup mechanism for relay nodes selection and communication circuit construction. • P2P: Peer to Peer • DHT: Distributed Hash Table

  4. The problem: TOR would not scale • General framework for anonymous networking: • Centralized schemes: • All traffic flows over a small, constant routes, • Trivial relay discovery, • Limited # of users. • P2P: • Relay and client • More scalable • Unstable service • Various attack, due to imperfect knowledge.

  5. The problem: TOR would not scale • TOR is a hybrid of: • (Centralized) trusted directory servers • Maintain a good list of active relays. • (P2P) all nodes (freely) can join as a relay or client • Available bandwidth increases as more nodes (relay) join • Seems all right since: • You know which relay to trust, • You have more bandwidth as more relays joins. As of 2009: 10K simultaneous users,2K relay nodes.

  6. The problem: TOR would not scale • A closer look: • Each client needs to know the all relays info to select relays, periodically. • Relay info: status docs, router descriptors(pubic key, exit policy…) … • And all these request are filled by trusted directory servers! • Directory servers (DS) may overload. • Even if we have sufficient DS, the whole Tor network is flooded with relay info.

  7. The prolem: TOR would not scale

  8. The problem: TOR would not scale • Let’s quantify: • Bandwidth needed for relay info O(nr), • n: # of users • r: # of relays • Bandwidth provided by relay: O(r)

  9. The solution: TORSK • Introducing TORSK: • A new design for a low-latency anonymous networking scheme • Better scalability • Introduces no new attack • Incrementally deployable: relays can serve both Tor and Torsk. • O(n log r): bandwidth spent on relay selection (relay info)

  10. The solution: TORSK • How: • By using NA BS DHT • NA: Neighborhood Authority • BS: Buddy Support • DHT: Distributed Hash Table

  11. The solution: TORSK • Background: TOR • Providing anonymity by using encrypted circuit for traffic. • (Default) circuit length = 3, • Entry node .. Knows sender, but not receiver • Intermediate node .. Knows entry/exit nodes • Exit node .. Knows receiver, but not sender • Three types of node: • OP: onion proxy, client • OR: onion router, relay • DS: directory server,

  12. The solution: TORSK • Background: DHT • Each node holds a piece of hash table • A look up process: • A node wants to file look up request, s/he must know where this request can be served. • Some nodes may provide routing info, so the initializer node knows where to send the look up request. • The node sends look up request to the right node, so that a look up can be done there. • What is the benefit of “a piece of hash table”? • Well, e.g. Wichita’s post office does not need New York’s street addr. • O(nr) vs. O(n log r)

  13. The solution: TORSK • Background: DHT • Attacks to DHT: • Misrouting • Passive logging • Selective dropping • Route fingerprinting • … • That is why we need NABSDHT • NA: Neighborhood Authority • BS: Buddy Support

  14. The solution: TORSK • We do have NA DHT: Myrmic • Myrmic: • Issues certificate (relatively long term) to each node • Node’s neighbors keep eyes on each other • So a node can hardly claim something incorrect • Myrmicsolves: • Misrouting • Selective dropping

  15. The solution: TORSK • Everything set? Not really. • E.g., “Hi, I am writing to you to verify that …” • What you verified exposed your interest/node/circuit. • Also, looking up a node is kind of multicast. • You send to multiple nodes to do the look up.

  16. The solution: TORSK • OK, since looking up and verifying are exposing, how about we delegate these jobs to someone else? • That is NA BS DHT • BS: buddy support • More stranger than buddy • Perform random walk to select a buddy

  17. The solution: TORSK

  18. The solution: TORSK

  19. The solution: TORSK • That is general idea of Torsk. • Does it work? • According to the author, yes. • Tons of technique details. • E.g.

  20. Thank you!

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