privacy-preserving p2p data sharing with oneswarm -piggy
Post on 11-Jan-2016
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Privacy-Preserving P2P Data Sharing with OneSwarm
-Piggy
Outline
• Overview• Related Works• Data Sharing with OneSwarm• Protocol Design• Security Analysis• Evaluation
Overview
• P2P file sharing is efficient and common• Most P2P application allow third parties to
monitor users behaviour• Privacy
-the protection of information from unauthorized disclosure
• Attackers can get some privacy information by observing user behaviourex: using BitTorrent to download security patch
Related Works
• BitTorrentA common P2P file sharing protocol with high efficiency but without privacy protection
• TorUses onion routing techniques to anonymize request via a set of relay nodes
• FreenetUses an anonymous P2P publishing system
Data Sharing with OneSwarm
• An exmaple
Data Sharing with OneSwarm
• Public distribution• Everyone in the network can download file freely• All data need not be private• Serves as a fully backwards compatible BitTorrent
client
Data Sharing with OneSwarm
• With permission• Only users with permission can download files• Uses persistent identities to define per-file
permission• Allows all permitted users to recognize one
another and engage in swarming downlod
Data Sharing with OneSwarm
• Without attribution• Depends on obscuring attribution of source
and/or destination• Instead of directly advertise data, it uses privacy-
preserving keyword search• Data is relayed through unknown number of
intermediaries• Apprpriate for sensitive material
Protocol Design
• Two major tasks• Defining and maintaining the overlay topology• Locating and transferring data objects
• Topology• Define overlay links by exchanging public keys• Peers are either trusted or untrusted
Protocol Design
• Transport• The mesh defined by the web of trust among users is ued to
locate and transfer data• Inspired by existing P2P swarming systems e.g., BitTorrent• Restrics direct communication to a small number of
persistent contacts• Locates distant data source by flooding through the overlay• Data transfers occur over the reverse search path• Obscuring the identities of sender and receiver when
sharing data without attribution
Protocol Design
• Linking Peers with Trust relationships• 1024 bit RSA public/private key pair, public key
serves as its identity (persistent) among its peers• Key exchange• Discover and exchange over local area network• Piggy-back on existing social network e.g., Google Talk• By email invitations
Protocol Design
• Managing Groups and Trusted Peers• Private Community Server• Maintains a list of registered users• Provides authorized subscibers with a current set of
public keys
• Public Community Server• Allows new users to easily obtain a set of untrusted
peers
Protocol Design
• Identity and Connectivity• Long-term identities are linked to transient IP and
port number via DHT• DHT entries are encrypted with public key• ID->{IP, Port}• Various key exchange + DHT => overlay mesh
Protocol Design
• Naming and Locating Data• Between connected peers => exchange file list• Naming• 160 bit SHA-1 hash of name and content• Low order 6 bit => file ID in search message
• Congestion Aware Search• Tradeoff between overhead and performance• Shortest path• Management of propagation of searches
Protocol Design
• Naming and Locating Data• Congestion Aware Search• Search message don’t have time-to-live• Maintaining a set of rotating Bloom filter and forward
search message if the forwarder had idle cpacity and hasnot yet forwrded it• Forward to untrusted peer probabilistically• Delay 150ms before forwarding• Terminate with search cancel message
Protocol Design
• Naming and Locating Data• Path Setup• Search message matched => search reply (delayed)• Search identifier• Path identifier
Protocol Design
• Swarming Data Transfer• Keep alive message refresh path• Tunnels BitTorrent traffic through overlay paths• Dicover new path by periodically flooding search
message• Enhance load balance and efficiency
Protocol Design
• Incentives• Client maintain tansfer statistics for each peer• Retain tic-for-tac in BitTorrent• Contention => weight decided by ratio of
contribution and net consumption• Forwarding is sum to 0
Security Analysis
• Goal• Improve privacy by allowing users to control
information disclosure• Resistent to the disclosure of user behaviour to an
attacker with control over a limited # of overlay nodes
Security Analysis
• Attacks and Defenses• Persistent peering relationship limit monitoring
power• Heterogeneity of trust relationship foils timing
attacks• Lack of source routing limits correlation attacks• Constrained reandomness frustrates statistical
attacks• Network dynamics limit value of historical data
Security Analysis
• Timming Attacks
Security Analysis
• Collusion Attacks
Evaluation
• Overlay structure
Evaluation
• Multiple-path Transfer
Evaluation
• Comparison with existing systems
Evaluation
• Overhead
Evaluation
• Utilization
Conclusion
• Strength• Data collected from real world
• Weakness• Not well organized
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