Constant-Rounds, Almost-Linear Bit-Decomposition of Secret Shared Values

  • Authors:
  • Tomas Toft

  • Affiliations:
  • CWI Amsterdam, The Netherlands and TU Eindhoven, The Netherlands

  • Venue:
  • CT-RSA '09 Proceedings of the The Cryptographers' Track at the RSA Conference 2009 on Topics in Cryptology
  • Year:
  • 2009

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Abstract

Bit-decomposition of secret shared values --- securely computing sharings of the binary representation --- is an important primitive in multi-party computation. The problem of performing this task in a constant number of rounds has only recently been solved. This work presents a novel approach at constant-rounds bit-decomposition. The basic idea provides a solution matching the big-$\mathcal{O}$-bound of the original while decreasing the hidden constants. More importantly, further solutions improve asymptotic complexity with only a small increase in constants, reducing it from $\mathcal O(\ell{\rm log}(\ell))$ to $\mathcal O({\ell}{\rm log}^*(\ell))$ and even lower. Like previous solutions, the present one is unconditionally secure against both active and adaptive adversaries.