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Auction-based Model of BitTorrent

Auction-based Model of BitTorrent. Seminar in Distributed Computing 2010 ETH Zurich Yu Li. What is BitTorrent. How to download using BitTorrent. STEP 1: Select Torrent File. STEP 2: Download Torrent. How to download using BitTorrent. STEP 3: Configuration. STEP 4: Download File.

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Auction-based Model of BitTorrent

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  1. Auction-based Model of BitTorrent Seminar in Distributed Computing 2010 ETH Zurich Yu Li

  2. What is BitTorrent

  3. How to download using BitTorrent STEP 1: Select Torrent File STEP 2: Download Torrent

  4. How to download using BitTorrent STEP 3: Configuration STEP 4: Download File

  5. Downloading procedure • Individuals View • Seed • Leecher

  6. Downloading procedure • System View • I upload and download at the same time … … Me

  7. Auction-based Model[D. Levin, K. LaCurts, 2008] "BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives" (Q1) Do I upload to everyone? … … … … Me Me

  8. Auction-based Model (Q2) Do I treat every peer equally? … … … … 2 6 4 2 4 2 6 1 3 2 2 2 Me (6Mbps) Me (6Mbps)

  9. Auction-based Model (Q3) Do I ignore others? … … … … 0.1 0.2 6 4 2 4 2 6 2 2 2 0.2 1.5 1.5 0.1 1.5 1.5 Me (6Mbps) Me (6Mbps)

  10. Auction-based Model • Bids are uploads of round n-1 • Auction clearing 1 random peer Highest S-1 18 12 3 2 1 18 12 3 2 1 W/S W/S W/S W/S Me (Bandwidth W) Me (Bandwidth W) Round n Round n-1 Select S peers (S=4)

  11. Sybil Attack • Normal Bidder “Red” bidder gets 18Mbps n-1 round 18 12 3 2 1 n round 18Mbps 18Mbps 18Mbps 18Mbps Auctioneer (Me) provides 72Mbps bandwidth in total

  12. Sybil Attack • Selfish Bidder 12 “Red” bidder sybil gets 2×18Mbps n-1 round 18 4 4 4 3 2 1 n round 18Mbps 18Mbps 18Mbps 18Mbps Auctioneer (Me) provides 72Mbps bandwidth in total

  13. Review of Question 2 • (Q2) Do I treat every peer equally? … … … … 2 6 4 2 4 2 6 1 3 2 2 2 Me (6Mbps) Me (6Mbps)

  14. Countermeasure:Proportional share auction • Proportional share “Red” bidder gets 24Mbps n-1 round 18 12 3 2 1 n round 6 36Mbps 24Mbps 4 2

  15. Countermeasure:Proportional share auction • Sybil attack resilient “Red” bidder sybil gets 3×8=24Mbps 12 18 4 4 4 3 2 1 n-1 round n round 6 8Mbps 36Mbps 8Mbps 8Mbps 4 2

  16. Comparison of Auction-based &Propshare • Propshare is Sybil proof

  17. Under-reporting • Which one is better for me? X Y X Y X X Y Y A B A B Under-reporting X Y X Y X Y X Y A B Me Me X Y X Y Y X X X Y Y Me A B A B X X X X Y Y Me Me

  18. Under-reporting • Under-reporting algorithm • Run algr. when peer is about to lose interest. • Determine the most common piece among available X Y Z X Y Z X X X Y Y Y Z Z Z Alice Tom Peer 1 Peer 3 Peer 2 X X X Y Y Y Z X Z Z X Y Y Z Z Peer 1 Peer 3 Tom Alice Peer 2

  19. Under-reporting

  20. Y Z X Countermeasure: Gossiping Me A X Y Z Z Costs overhead B

  21. Countermeasure: TrInc[D.Levin, J.R. Douceur 2009] "TrInc: Small Trusted Hardware for Large Distributed Systems" • TrInc (Trusted Incrementer) • Prevents lying • Decreases overhead • TPM (Trusted Platform Module) by Intel

  22. Countermeasure: TrInc • System equipped with TrInc

  23. Countermeasure: TrInc • Individual equipped with TrInc

  24. Countermeasure: TrInc • How does TrInc work? BitField New Counter Value New Counter Value Encryption Old Counter Value BitField + New Counter Value + Old Counter Value

  25. Countermeasure: TrInc • Input • New Counter Value • BitField • Output • Attestation • Sample Output A D Y Z B C … A D Y Z B C  … G A D E F B C 34

  26. Countermeasure Me A X Y Z Z Y Z X B

  27. X X X X X X X Y Y Y Y Y Y Y Z Z Z Z Z Z Z T T T T T T T Nonce Nonce 1  2 1  2 0  1 0  1 2  3 2  3 2  3 3  3 3  3 Countermeasure: TrInc D Bitfield Request Nonce C Piece Providing Z Me B Piece Providing Y A Piece Providing X

  28. Countermeasure: TrInc • Individual equipped with TrInc

  29. Auction-based Model • TrInc • Q & A

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