Time-selective convertible undeniable signatures

  • Authors:
  • Fabien Laguillaumie;Damien Vergnaud

  • Affiliations:
  • ,France Telecom Research and Development, Caen Cedex 4, France;Laboratoire de Mathématiques Nicolas Oresme, Université de Caen, Caen Cedex, France

  • Venue:
  • CT-RSA'05 Proceedings of the 2005 international conference on Topics in Cryptology
  • Year:
  • 2005

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Abstract

Undeniable signatures were introduced in 1989 by Chaum and van Antwerpen to limit the self-authenticating property of digital signatures. An extended concept – the convertible undeniable signatures – proposed by Boyar, Chaum, Damgård and Pedersen in 1991, allows the signer to convert undeniable signatures to ordinary digital signatures. We present a new efficient convertible undeniable signature scheme based on bilinear maps. Its unforgeability is tightly related, in the random oracle model, to the computational Diffie-Hellman problem and its anonymity to a non-standard decisional assumption. The advantages of our scheme are the short length of the signatures, the low computational cost of the signature and the receipt generation. Moreover, a variant of our scheme permits the signer to universally convert signatures pertaining only to a specific time period. We formalize this notion as the time-selective conversion.