International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Unconditionally Secure Rational Secret Sharing in Standard Communication Networks

Zhifang Zhang
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Abstract: Rational secret sharing protocols in both the two-party and multi-party settings are proposed. These protocols are built in standard communication networks and with unconditional security. Namely, the protocols run over standard point-to-point networks without requiring physical assumptions or simultaneous channels, and even a computationally unbounded player cannot gain more than $\epsilon$ by deviating from the protocol. More precisely, for the $2$-out-of-$2$ protocol the $\epsilon$ is a negligible function in the size of the secret, which is caused by the information-theoretic MACs used for authentication. The $t$-out-of-$n$ protocol is $(t-1)$-resilient and the $\epsilon$ is exponentially small in the number of participants. Although secret recovery cannot be guaranteed in this setting, a participant can at least reduce the Shannon entropy of the secret to less than $1$ after the protocol. When the secret-domain is large, every rational player has great incentive to participate in the protocol.
  title={Unconditionally Secure Rational Secret Sharing in Standard Communication Networks},
  booktitle={IACR Eprint archive},
  keywords={cryptographic protocols / rational secret sharing, $\epsilon$-Nash equilibrium, unconditional security},
  note={ 14852 received 30 Aug 2010},
  author={Zhifang Zhang},