How Fair is your Protocol? A Utility-Based Approach to Protocol Optimality
summary
Defines a utility-based fairness metric that assigns values gamma_{1,0}, gamma_{0,1}, gamma_{1,1}, etc., then models protocol design as a zero-sum meta-game and proves an absolute subgame-perfect equilibrium. Builds a two-party protocol that uses an unfair SFE subprotocol to output a random index and authenticated shares, yielding outcomes where the adversary fully wins in ~50% of cases and both get outputs in ~50% (50% full win), and proves this payoff is optimal via a simulator-min payoff argument and simulation-based ideal functionality. Extends to multi-party monotone payoff curves and area-optimality.
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chapters (15)
- 0:00Intro
- 0:20Question
- 6:36Relaxed Fairness
- 8:03Duration of Protocol Design
- 9:17Functionality
- 12:30Events
- 13:00Payoff
- 15:10Proof
- 19:15An adversary strategy
- 21:18Proof idea
- 23:03Multiparty case
- 24:11Standard SFE
- 26:10Rational SFE
- 27:45Protocol Design Framework
- 28:46Rational Commitment
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