Unconditional Byzantine Agreement and Multi-party Computation Secure against Dishonest Minorities from Scratch

  • Authors:
  • Matthias Fitzi;Nicolas Gisin;Ueli M. Maurer;Oliver von Rotz

  • Affiliations:
  • -;-;-;-

  • Venue:
  • EUROCRYPT '02 Proceedings of the International Conference on the Theory and Applications of Cryptographic Techniques: Advances in Cryptology
  • Year:
  • 2002

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Abstract

It is well-known that n players, connected only by pairwise secure channels, can achieve unconditional broadcast if and only if the number t of cheaters satisfies t n/3. In this paper, we show that this bound can be improved - at the sole price that the adversary can prevent successful completion of the protocol, but in which case all players will have agreement about this fact. Moreover, a first time slot during which the adversary forgets to cheat can be reliably detected and exploited in order to allowfor future broadcasts with t n/2. This even allows for secure multi-party computation with t n/2 after the first detection of such a time slot.