Public Key Cryptography – PKC 2004

Volume 2947 of the series Lecture Notes in Computer Science pp 262-276

Identity-Based Threshold Decryption

  • Joonsang BaekAffiliated withSchool of Network Computing, Monash University
  • , Yuliang ZhengAffiliated withDept. Software and Info. Systems, UNC Charlotte


In this paper, we examine issues related to the construction of identity-based threshold decryption schemes and argue that it is important in practice to design an identity-based threshold decryption scheme in which a private key associated with an identity is shared. A major contribution of this paper is to construct the first identity-based threshold decryption scheme secure against chosen-ciphertext attack. A formal proof of security of the scheme is provided in the random oracle model, assuming the Bilinear Diffie-Hellman problem is computationally hard. Another contribution of this paper is, by extending the proposed identity-based threshold decryption scheme, to construct a mediated identity-based encryption scheme secure against more powerful attacks than those considered previously.