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Towards Rational Consensus in Honest Majority

Series: Department Seminar

Speaker: Varul Shrivastava, PhD student, IIIT Hyderabad

Date/Time: Mar 13 14:30:00

Location: CSA Conference Room, (Room No. 101, Ground floor) - on Teams

Abstract:
Distributed consensus protocols reach agreement among ?? players in the presence of ?? adversaries; different protocols support different values of ?? . Existing works study this problem for different adversary types (captured by threat models). There are three primary threat models: (i) Crash fault tolerance (CFT), (ii) Byzantine fault tolerance (BFT), and (iii) Rational fault tolerance (RFT), each more general than the previous. Agreement in repeated rounds on both (1) the proposed value in each round and (2) the ordering among agreed-upon values across multiple rounds is called Atomic BroadCast (ABC). ABC is more generalized than consensus and is employed in blockchains. This work studies ABC under the RFT threat model. We consider ?byzantine and ?? rational adversaries among ?? players. We also study different types of rational players based on their utility towards (1) liveness attack, (2) censorship or (3) disagreement (forking attack). We study the problem of ABC under this general threat model in partially-synchronous networks. We show (1) ABC is impossible for ??/3 < (? + ??) < ??/2 if rational players prefer liveness or censorship attacks and (2) the consensus protocol proposed by Ranchal-Pedrosa and Gramoli cannot be generalized to solve ABC due to insecure Nash equilibrium (resulting in disagreement). For ABC in partially synchronous network settings, we propose a novel protocol pRFT(practical Rational Fault Tolerance). We show pRFT achieves ABC if (a) rational players prefer only disagreement attacks and (b) ? < ??/4 and (? + ??) < ??/2 . In pRFT, we incorporate accountability (capturing deviating players) within the protocol by leveraging honest players. We also show that the message complexity of pRFT is at par with the best consensus protocols that guarantee accountability.

Speaker Bio:
Varul Shrivastava is a PhD student at IIIT Hyderabad working with Prof. Sujit Gujar. He is interested in Game theory, Cryptography and Mechanism Design. Microsoft Teams Join the meeting now Meeting ID: 472 550 233 423 Passcode: CfSotE https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZjA3NzMyM2ItNjNiZS00ODhjLWFmMmQtNWNmMTExZTU4YTNk%40thread.v2/0?context=%7b%22Tid%22%3a%226f15cd97-f6a7-41e3-b2c5-ad4193976476%22%2c%22Oid%22%3a%221beaa166-3a14-437e-9106-75a2e2caebeb%22%7d

Host Faculty: Prof. Chaya Ganaesh