Key-dependent message security for division function: discouraging anonymous credential sharing

  • Authors:
  • Xianhui Lu;Bao Li;Qixiang Mei;Haixia Xu

  • Affiliations:
  • State Key Laboratory of Information Security, Graduate University of Chinese Academy of Sciences, Beijing, China;State Key Laboratory of Information Security, Graduate University of Chinese Academy of Sciences, Beijing, China;School of Information, Guangdong Ocean University, Zhanjiang, China;State Key Laboratory of Information Security, Graduate University of Chinese Academy of Sciences, Beijing, China

  • Venue:
  • ProvSec'11 Proceedings of the 5th international conference on Provable security
  • Year:
  • 2011

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Abstract

Key-dependent message (KDM) security means that the encryption scheme remains secure even encrypting f(sk), where f is an efficient computable function chosen by the adversary and sk = sk1,..., skn are private keys. We concentrate on a special case that the function f is a division function. Namely, the messages of the form ski/skj are encrypted. We prove that if a public key encryption (PKE) scheme is IND-CPA (chosen plaintext attacks) secure and has the properties of public-key blinding and secret-key homomorphism, then it is KDM secure for division function (KDM-div secure). For concrete scheme, we show that the hybrid ElGamal scheme is KDM-div secure based on the decisional Diffie-Hellman (DDH) assumption in the standard model. We show that KDM-div secure scheme is useful in the design of anonymous credential systems.