Paper 2003/164

Identity-Based Threshold Decryption

Joonsang Baek and Yuliang Zheng


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.

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Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. A short version of this paper is to appear in the proceedings of PKC 2004.
Contact author(s)
joonsang baek @ infotech monash edu au
2003-12-24: last of 6 revisions
2003-08-11: received
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      author = {Joonsang Baek and Yuliang Zheng},
      title = {Identity-Based Threshold Decryption},
      howpublished = {Cryptology ePrint Archive, Paper 2003/164},
      year = {2003},
      note = {\url{}},
      url = {}
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