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Game Authority for Robust and Scalable Distributed Selfish-Computer Systems Shlomi Dolev, BGU (Israel) Elad M. Schiller, Chalmers (Sweden) Paul G. Spirakis,

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Presentation on theme: "Game Authority for Robust and Scalable Distributed Selfish-Computer Systems Shlomi Dolev, BGU (Israel) Elad M. Schiller, Chalmers (Sweden) Paul G. Spirakis,"— Presentation transcript:

1 Game Authority for Robust and Scalable Distributed Selfish-Computer Systems Shlomi Dolev, BGU (Israel) Elad M. Schiller, Chalmers (Sweden) Paul G. Spirakis, CTI (Greece) Philippas Tsigas, Chalmers (Sweden)

2 The system designer Distributed computing assumes identical programs. How to design distributed algorithms for the wild internet? Let’s play the prisoner dilemma game. Use game theory for selfish- computer systems.

3 The system designer B A SilentBetray Silent Betray (+1,+1) (+3,–1) (–1,+3) ( 0, 0) John Nash Game theory predicts: selfish-computer choose betray ! Yes, I trust game theory. OK... Let’s play in a real system.

4 The system designer We need a distributed game authority. O.K., we should explicitly enforce the implicit rules of the game. In a real system, where I am the only authority… they would be free to escape!

5 The Society Moral Code Complete anarchy exists without moral codes Game authority founded over the moral majority –choose and enforces the rules of the game –promote freedom of choice for the society’s benefit We promote honestly selfish behavior for the sake of: end-point creativity motivation for success

6 The Society Moral Code Complete anarchy exists without moral codes Game authority founded over the moral majority –choose and enforces the rules of the game –promote freedom of choice for the society’s benefit Benefits End-point success that yields global success Provable scalability from the days of Greece Provable robustness, still

7 Technical Contributions Cost Reduction: We replace the higher price of anarchy with the lower price of stability!

8 Technical Contributions Cost Reduction: We replace the higher price of anarchy with the lower price of stability! Price of anarchy (PoA) Worst case ratio between: NE’s social cost, and the social optimum Koutsoupias & Papadimitriou STACS’99 Social optimum Worst NE PoA Good Bad

9 Technical Contributions Social optimum Best NE PoS Good Bad Price of stability (PoS) Best case ratio between: NE’s social cost, and the social optimum Anshelevich et al. FOCS'04 Worst NE PoA Cost Reduction: We replace the higher price of anarchy with the lower price of stability!

10 Game Authority Implementation Can we assume that all components are selfish? –im possible: Phy. layer game & Mac layer game &, …, & possible failures & imprecise utility how to bound the PoA ? Social optimum Best NE PoS Good Bad Honest and moral based middleware tolerating Byzantine faults transient faults Facilitates interaction among honestly selfish agents Worst NE PoA Explicit ∞ Moral Code Middleware: Game Authority Application-layer: Honestly selfish agents (majority)

11 Implementation (cont.) Byzantine agreement Cryptographic primitives Game theory analysis How to decide on the preferable game? How does the honest majority audit the game? How to preserve privacy in simultaneous plays?

12 Your attention is appreciated More details: Technical report number TR-2006:9 Computer Science and Engineering Chalmers University of technology, 2006 Also, technical report, DELIS, Accessible via

13 Rabbi Akiva said: All is foreseen, but freedom of choice is given. The world is judged in goodness, yet all is proportioned to one's work. (Mishnah Pirkei Avot, Chapter 3, 19) הכול צפוי, והרשות נתונה; ובטוב העולם נידון. והכול לפי רוב המעשה, אבל לא על פי המעשה. (פרקי אבות, ג` ט"ו)


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