Cryptanalysis of a forward secure blind signature scheme with provable security

  • Authors:
  • Shuhong Wang;Feng Bao;Robert H. Deng

  • Affiliations:
  • School of Information Systems, SMU, Singapore;Institute for Infocomm Research (I2R), Singapore;School of Information Systems, SMU, Singapore

  • Venue:
  • ICICS'05 Proceedings of the 7th international conference on Information and Communications Security
  • Year:
  • 2005

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Abstract

A forward secure blind signature scheme was proposed by Duc, Cheon and Kim, in ICICS 2003. The security of the scheme was proved to be equivalent to the strong RSA assumption in the random oracle model. In this paper we present an attack to the scheme by forging valid signatures with public keys only. The attack is so efficient that forging a valid signature needs less computation than legally generating a signature, even considering only the user side. Our result implies that the security proof of the scheme must be invalid. Furthermore we point out the fault of the proof and explain why it invalidates the proof.