Privacy-Preserving P2P Data Sharing with OneSwarm

1. Privacy-Preserving P2P Data Sharing with OneSwarm Authors: Tomas Isdal, Michael Piatek, Arvind Krishnamurthy, Thomas Anderson Published In: ACM SIGCOMM, September 2010 Presented By: Muhammad` Faisal Amjad

2. Acknowledgement • Sources of figures / graphs / tables: • The paper being presented • http://oneswarm.cs.washington.edu/ • http://www.bittorrent.com/

3. Outline • Introduction to P2P file sharing • The Issue of Privacy in P2P file sharing • Overview of OneSwarm file sharing System • OneSwarm Protocol Design • Security Analysis • Contributions • Weaknesses • Suggested Improvements

4. Introduction to P2P file sharing Download from a single Source

5. Introduction to P2P file sharing Multiple Computers download the same file from a single Source

6. Introduction to P2P file sharing Torrent File Every Computer becomes part of a network of sources of the same file

7. Introduction to P2P file sharing From where to get different pieces of the file ?

8. Introduction to P2P file sharing A “Tracker” gives info about various sources called “Peers”, for the file

9. Privacy ???

10. The Issue of Privacy in P2P file sharing • Protocols like BitTorrent offer high performance and robustness but participants can easily be monitored by anyone who cares • Anonymization networks e.g. Tor and FreeNet offer privacy but at the cost of performance • Available P2P file sharing systems offer an un-attractive choice between privacy and performance

11. OneSwarm File Sharing System

12. Overview • Central to the design is the notion of “flexible privacy” and “friend-to-friend sharing”. • Instead of relying only on a directory service such as a “Tracker” to discover peers, OneSwarm builds trusted links through social network peers • Users are free to control the tradeoff between performance and privacy by managing the level of trust in peers.

14. Overview of OneSwarm file sharing System - Search Searching for a file through a chain of friends OR Peers

15. Overview of OneSwarm file sharing System - Response File is sent on the reverse path

16. Overview of OneSwarm file sharing System - Anonymity Receiver’s perspective of the source of file

17. Overview of OneSwarm file sharing System - Anonymity Sender’s perspective of the destination of file

18. Protocol Design • OneSwarm protocol supports two tasks: • Defining and maintaining the overlay topology • Locating and transferring data objects

19. Protocol Design - Tasks • 1) Defining and maintaining the overlay topology • Bootstrapping the mesh network: Exchange of encryption keys • Social Network Import – Email, Social NW or LAN • Community Servers • Manually • Name resolution: Distributed Hash Table is maintained by every user serves as the name resolution service. Contains encrypted IDs and their mapping for IP / Port

20. Protocol Design - Tasks • 2) Locating and transferring data objects • Congestion-aware Search: Controlled flooding of search queries to locate data and construct forwarding paths without overwhelming the network or exposing endpoints. • Swarming Data Transport: Data is split into blocks, with active downloaders redistributing completed blocks. Transfers use multiple paths and multiple sources, if available. • Long Term History: Each client maintains transfer volumes for each peer, using these to prioritize service during periods of congestion.

21. So… How does OneSwarm Provide Privacy

22. Privacy Levels provided by OneSwarm • Public Distribution – Same as BitTorrent* • Without Attribution • Multi-hop (chain of friends) instead of direct P2P transfer • Changing source + destination IP addresses & Ports at every hop • With Permission – Peer identities and resource names are shared only through Public/Private key combinations • *All OneSwarm transfers are encrypted

23. Privacy Levels provided by OneSwarm

24. Security Analysis – Attacks & Defenses • Timing Attack – Search queries and responses are forwarded after adding a random delay to inhibit calculation of RTT to infer proximity • Correlation Attack – Peers have limited view of the overlay and cannot control path setup beyond directly connected neighbors. Attackers could use this to correlate performance with ongoing transfers • Collusion Attack - Search queries and responses are forwarded probabilistically, making it very hard for directly connected colluding peers to infer source of data or monitor habits

25. Performance Evaluation • File Size – 20 MB • 120 PlanetLab machines • To limit overhead, Tor was modified to create 10 new paths every 10 seconds • instead of every 10 minutes

26. Contributions • A new system that provides flexibility for the user to manage the level of privacy for file sharing • Incorporation of social network for building p2p file sharing network

27. Weaknesses • Evaluation of Protocol in “Privacy-Preserving” modes • No details are provided regarding the implementation / functioning of community servers • Manual bootstrapping of mesh topology has not been explained

28. Improvements • Capability to import friends from other social networks

29. Questions