Detection of Cheaters in Vector Space Secret Sharing Schemes

  • Authors:
  • Carles Padro;Germán Sáez;Jorge Luis Villar

  • Affiliations:
  • -;-;Departament de Matemàtica Aplicada i Telemàtica, Universitat Politècnica de Catalunya, Modul C3, Campus Nord, c/Jordi Girona, 1-3, 08034 Barcelona, Spain

  • Venue:
  • Designs, Codes and Cryptography
  • Year:
  • 1999

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Abstract

Aperfect secret sharing scheme is a method of distributing sharesof a secret among a set P of participants in sucha way that only qualified subsets of P can reconstructthe secret from their shares and non-qualified subsets have absolutelyno information on the value of the secret. In a secret sharingscheme, some participants could lie about the value of theirshares in order to obtain some illicit benefit. Therefore, thesecurity against cheating is an important issue in the implementationof secret sharing schemes. Two new secret sharing schemes inwhich cheaters are detected with high probability are presentedin this paper. The first one has information rate equal to 1/2and can be implemented not only in threshold structures, butin a more general family of access structures. We prove thatthe information rate of this scheme is almost optimal among allschemes with the same security requirements. The second schemewe propose is a threshold scheme in which cheaters are detectedwith high probability even if they know the secret. The informationrate is in this case 1/3. In both schemes, the probabilityof cheating successfully is a fixed value that is determinedby the size of the secret.