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Bitcoins Transaction Processing Yonatan Sompolinsky joint work with Aviv Zohar.

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Presentation on theme: "Bitcoins Transaction Processing Yonatan Sompolinsky joint work with Aviv Zohar."— Presentation transcript:

1 Bitcoins Transaction Processing Yonatan Sompolinsky joint work with Aviv Zohar

2 Bitcoin hard to get easy to pass no authority, no money printing pseudonymous relatively secure ?high transaction volume decentralized cryptocurrency current protocol: conflict ghost protocol: in accord

3 Transactions in Bitcoin tx Bob Calvin ?irreversible tx

4 txs: block #81block #82 block #83 The Blockchain txs: ~ 10 min consistent grows in time kept locally at each node Time

5 A B2 B1 maintain one main chain only blocks discarded & txs cancelled Conflicting blockchains the longest chain rule delays => forks Time

6 Block tree vs Block chain λ:= block creation rate = 6 per hour β:= growth rate of main chain = 4 per hour efficiency:= β/λ=4/6<1 Time delays => forks => inefficiency

7 Block size, Delay & Efficiency analysis of data provided to us by Decker and Wattenhofer λ = block creation rate β = growth rate of main chain 0.95 Block Propagation Time

8 Throughput (TPS) Transactions Processed per Second = (block size) X (growth rate of the main chain) /600 TPS ~ 1736 TPS < 3.3 why?

9 Security - double spend attack tx Bob Calvin tx secret tx main chain publish !

10 Success of attack

11 Effect of increasing throughput efficiency security TPS delay

12 Security limitation on TPS attacker computational power (fraction) TPS Bitcoin today: secure but low throughput high TPS: more bandwidth needed secure TPS vulnerable TPS

13 Greedy Heaviest Observed Sub-Tree longest chain efficiency security

14 Greedy Heaviest Observed Sub-Tree B C1 A C2 C3 D1 D2 D3 E1 tx B tx main chain according to longest rule main chain according to ghost Time

15 GHOST throughput no security constraint hardware constraints, e.g., network congestion, limit the feasible TPS 8.5-fold increase of current bandwidth can withstand TPS = 2000 in pipeline: improvement of ghost, same bandwidth more TPS … security high transaction volume

16 https://eprint.iacr.org/2013/881.pdf


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