Paper 2022/1762

On the impossibility of surviving (iterated) deletion of weakly dominated strategies in rational MPC

Johannes Blömer, Paderborn University
Jan Bobolz, Paderborn University
Henrik Bröcher, Paderborn University

Rational multiparty computation (rational MPC) provides a framework for analyzing MPC protocols through the lens of game theory. One way to judge whether an MPC protocol is rational is through weak domination: Rational players would not adhere to an MPC protocol if deviating never decreases their utility, but sometimes increases it. Secret reconstruction protocols are of particular importance in this setting because they represent the last phase of most (rational) MPC protocols. We show that most secret reconstruction protocols from the literature are not, in fact, rationally sound with respect to weak domination. Furthermore, we formally prove that (under certain assumptions) it is impossible to design a rationally sound secret reconstruction protocol if (1) shares are authenticated or (2) half of all players may form a coalition.

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Game TheoryRational Secret SharingMultiparty ComputationRational CryptographyWeakly Dominated Strategies
Contact author(s)
bloemer @ uni-paderborn de
jan bobolz @ uni-paderborn de
henrik broecher @ uni-paderborn de
2022-12-27: approved
2022-12-23: received
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      author = {Johannes Blömer and Jan Bobolz and Henrik Bröcher},
      title = {On the impossibility of surviving (iterated) deletion of weakly dominated strategies in rational MPC},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1762},
      year = {2022},
      note = {\url{}},
      url = {}
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