Having fun with p2p
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Having Fun with P2P. Keith W. Ross Polytechnic University http://cis.poly.edu/~ross. Many Apps Migrating Client-Server to P2P. File sharing File and patch distribution Live video streaming Video on demand VoIP Hybrid CDN/P2P. Today’s Talk. P2P security Is BitTorrent Unstoppable?

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Having Fun with P2P

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Having Fun with P2P

Keith W. Ross

Polytechnic University

http://cis.poly.edu/~ross


Many Apps Migrating Client-Server to P2P

  • File sharing

  • File and patch distribution

  • Live video streaming

  • Video on demand

  • VoIP

  • Hybrid CDN/P2P


Today’s Talk

  • P2P security

    • Is BitTorrent Unstoppable?

  • Survey of P2P video streaming research

    • Creating an open P2P video streaming ecosystem

Research supported by: NSF, Microsoft, Movie Labs, Huawei, Verizon, Panasonic, Len Shustek


Why study P2P Security?

  • P2P is potentially more vulnerable than client server.

  • Need to understand the security issues for architecting future P2P apps

  • Attacks from entertainment industry reveal weak spots in P2P


Security work joint with:

Jian Liang

Naoum Naoumov

Rakesh Kumar

Prithula Dhungel

Xiaojun Hei

Di Wu


Earlier work onKazaa and eDonkey

  • FastTrack/Kazaa

    • Unstructured P2P network

  • Overnet/Kad

    • Structured (DHT) P2P network

    • Part of eDonkey/eMule


File Pollution: Infocom 05

original content

polluted content

pollution

company


File Pollution

pollution

server

pollution

company

file sharing

network

pollution

server

pollution

server

pollution

server


File Pollution

Unsuspecting users

spread pollution !


File Pollution

Unsuspecting users

spread pollution !

Yuck


Index Poisoning: Infocom 06

index titlelocationbigparty 123.12.7.98smallfun 23.123.78.6heyhey 234.8.89.20

23.123.78.6

123.12.7.98

file sharing

network

234.8.89.20


Index Poisoning

index titlelocationbigparty 123.12.7.98smallfun 23.123.78.6heyhey 234.8.89.20

index titlelocationbigparty 123.12.7.98smallfun 23.123.78.6heyhey 234.8.89.20bighit 111.22.22.22

23.123.78.6

123.12.7.98

234.8.89.20

111.22.22.22


FastTrack Copies


Overnet Copies


Is BitTorrent Unstoppable?

(IPTPS 2008; extended version available)

  • How can record/movie companies limit piracy in BitTorrent?

    • Suing companies?

    • Suing users?

    • Internet attacks?

  • How vulnerable is BitTorrent to attacks?


BitTorrent

torrent: group of

peers exchanging

chunks of a file

tracker: tracks peers

in torrent; providestracker list

trading

chunks

torrent index server:search for torrents;provides .torrent file

peer


BitTorrent Ecosystem

  • Open protocol

    • 50+ client implementations

    • Dozens of tracker implementations

    • Dozens of torrent location sites

  • 5 million simultaneous users & growing

  • Evolving:

    • Peer discovery: DHTs, gossiping

    • Proprietary protocols, private torrents


Seeds and leechers

File divided into 256KB pieces. Each piece is 16 blocks.

Download blocks and assemble pieces

Hash piece to check integrity

Peers advertise pieces they have to neighbors

Peer sends blocks to four neighbors currently sending it data at the highest rate

And also to one random neighbor

BitTorrent Basics


Classes of BitTorrent Attacks

Attacks against an existing torrent

  • against leechers

  • against initial seed

  • against peer discovery

  • against peer discover

    Decoy attacks: attacker creates own torrent

  • Seeding a polluted file

  • Seeding a file and delivering only 99%


Fake Block Attack

  • Attacker establishes TCP connections with legitimate peers

  • Peer downloads one fake block from attacker

    • and 15 good blocks from legit peers

    • Hash failure – download is prolonged

Acknowledgment: Thanks to Vishal Misra for bringing this attack to our attention.


Simple analysis of fake block attack

What is the probability of a hash failure?

  • n = # neighbors advertising piece

  • m = attack nodes (m < n)

  • k = # neighbors from which it is downloading the 16 blocks


70% failure requires 20% attack neighbors

γ increases for rare pieces and in end game

Probability of a clean piece


Connection attack

  • Attacker establishes many TCP connections to each target peer.

    • Doesn’t upload any blocks

    • Chatty peer: keeps connection active with repeated BT handshake messages


Passive Measurements

  • Collect traces while downloading

    • Azureus and uTorrent

    • DSL and Ethernet

    • 54 downloads of “Foo Fighters” (108 MB)

  • Developed parser to analyze BT trace

  • To estimate download time without attack:

    • Obtain blacklist from torrentfreak.com

    • Use Peer Guardian to prevent connections to blacklisted peers


Azureus results

  • Download is NOT being prolonged by more than 50% for DSL


Zoom in one Azureus trace

Chatty-peers make upa major fraction of the useful peers.


Handshake messages sent by chatty peers


uTorrent


Zoom in on uTorrent trace


Passive Measurement Conclusions

  • Anti-P2P companies applying different strategies for different BT clients

  • Largely ineffective for Ethernet clients

  • For DSL, download time increases by 30-60%


Active Measurements

  • Crawl peers in torrent and identify

    • Fake-block attack peers

    • Chatty peers

  • Looked at 8 box-office movie torrents

    • Some under attack; some not

  • Crawler speaks Azureus protocol to Azureus peers

    • and conventional protocol to all other peers


Active Measurement Conclusions

  • Several, but not all, top-box movies are under attack

  • Published blacklists do not cover all the attackers in a torrent

  • Most attackers enter through gossiping


Seed Attack

  • “Nip in the bud”

  • Make many connections to seed, download at high rate

  • Rationale: Conventional algo gives all its bandwidth to 5 highest downloaders


Planet Lab experiments

  • Put 30 leechers on PL nodes; upload capacity capped at 512 kbps

  • Seed upload capacity 160 kbps

    • Azureus and uTorrent

  • 0-60 attack peers

  • Start seed, start 5 leechers, start attack peers, start 25 leechers


Seed attack results

delay

attacker bandwidth


BitTorrent Conclusions

  • Attacks against leechers can prolong downloads

    • But is 50% enough?

    • Blacklists are helpful; adaptive blacklist is needed

  • Seed is surprisingly resilient to attacks

  • Attacks must be tailored to client types

  • BitTorrent ecosystem is difficult to stop!


Today’s Talk

  • P2P security

    • Is BitTorrent Unstoppable?

  • Survey of P2P video streaming research

    • Creating an open P2P video streaming ecosystem

Research supported by: NSF, Microsoft, Movie Labs, Huawei, Verizon, Panasonic, Len Shustek


Live Streaming: Faculty Collaborators

ProfessorYong Liu

Professor

Shiv Panwar

Professor

Yao Wang

and Professor Nitsesh Saxena (CS)


obtain list

of peers

peer

Basic idea P2P live streaming

tracker

trade

chunks

Source

of video


PPLive: Chinese New Year 2006


@ Polytechnic

  • Infrastructure for measuring P2P live video systems

    • Xiaojun Hei, Jian Liang, Yong Liu

  • Stochastic modeling of P2P live streaming

    • Rakesh Kumar, Yong Liu

  • Incentives and scalable video for live P2P streaming

    • Zhengye Liu, Yanming Shen, Shiv Panwar, Yao Wang

  • Security of P2P live streaming systems

    • Prithula Dhungel, Xiaojun Hei, Nitesh Saxena

  • P2P VoD, Hybrid P2P-CDN

    • Angela Wang, MSR colleagues

  • Developing our own live P2P video system

    • Master’s students


Open P2P Live Streaming

  • Create an ecosystem for live streaming

  • Need incentives

    • The more you upload the better the quality

  • Layered video

    • Chunk-based

    • Substream-based

  • Accommodate user generated content


Thank You !


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