Annual International Conference on the Theory and Applications of Cryptographic Techniques

EUROCRYPT 2008: Advances in Cryptology – EUROCRYPT 2008 pp 527-544

David and Goliath Commitments: UC Computation for Asymmetric Parties Using Tamper-Proof Hardware

  • Tal Moran
  • Gil Segev
Conference paper

DOI: 10.1007/978-3-540-78967-3_30

Volume 4965 of the book series Lecture Notes in Computer Science (LNCS)

Abstract

Designing secure protocols in the Universal Composability (UC) framework confers many advantages. In particular, it allows the protocols to be securely used as building blocks in more complex protocols, and assists in understanding their security properties. Unfortunately, most existing models in which universally composable computation is possible (for useful functionalities) require a trusted setup stage. Recently, Katz [Eurocrypt ’07] proposed an alternative to the trusted setup assumption: tamper-proof hardware. Instead of trusting a third party to correctly generate the setup information, each party can create its own hardware tokens, which it sends to the other parties. Each party is only required to trust that its own tokens are tamper-proof.

Katz designed a UC commitment protocol that requires both parties to generate hardware tokens. In addition, his protocol relies on a specific number-theoretic assumption. In this paper, we construct UC commitment protocols for “David” and “Goliath”: we only require a single party (Goliath) to be capable of generating tokens. We construct a version of the protocol that is secure for computationally unbounded parties, and a more efficient version that makes computational assumptions only about David (we require only the existence of a one-way function). Our protocols are simple enough to be performed by hand on David’s side.

These properties may allow such protocols to be used in situations which are inherently asymmetric in real-life, especially those involving individuals versus large organizations. Classic examples include voting protocols (voters versus “the government”) and protocols involving private medical data (patients versus insurance-agencies or hospitals).

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Copyright information

© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • Tal Moran
    • 1
  • Gil Segev
    • 1
  1. 1.Department of Computer Science and Applied MathematicsWeizmann Institute of ScienceRehovotIsrael