Information theoretical analysis of two-party secret computation

  • Authors:
  • Da-Wei Wang;Churn-Jung Liau;Yi-Ting Chiang;Tsan-sheng Hsu

  • Affiliations:
  • Institute of Information Science, Academia Sinica, Taipei, Taiwan;Institute of Information Science, Academia Sinica, Taipei, Taiwan;Institute of Information Science, Academia Sinica, Taipei, Taiwan;Institute of Information Science, Academia Sinica, Taipei, Taiwan

  • Venue:
  • DBSEC'06 Proceedings of the 20th IFIP WG 11.3 working conference on Data and Applications Security
  • Year:
  • 2006

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Abstract

Privacy protection has become one of the most important issues in the information era. Consequently, many protocols have been developed to achieve the goal of accomplishing a computational task cooperatively without revealing the participants' private data. Practical protocols, however, do not guarantee perfect privacy protection, as some degree of privacy leakage is allowed so that resources can be used efficiently, e.g., the number of random bits required and the computation time. A metric for measuring the degree of information leakage based on an information theoretical framework was proposed in [2]. Based on that formal framework, we present a lower bound of the scalar product problem in this paper, and show that to solve the problem without the help of a third party, approximately half the private information must be revealed. To better capture our intuition about the secrecy of various protocols, we propose two more measurements: evenness and spread. The first measures how evenly the information leakage is distributed among the participants' private inputs. The second measures the size of the smallest set an adversary could use to obtain the same ratio of leaked information that could be derived in the worst case scenario.