Paper 2009/355

Asynchronous Distributed Private-Key Generators for Identity-Based Cryptography

Aniket Kate and Ian Goldberg


An identity-based encryption (IBE) scheme can greatly reduce the complexity of sending encrypted messages over the Internet. However, an IBE scheme necessarily requires a private-key generator (PKG), which can create private keys for clients, and so can passively eavesdrop on all encrypted communications. Although a distributed PKG has been suggested as a way to mitigate this problem for Boneh and Franklin's IBE scheme, the security of this distributed protocol has not been proven and the proposed solution does not work over the asynchronous Internet. Further, a distributed PKG has not been considered for any other IBE scheme. In this paper, we design distributed PKG setup and private key extraction protocols in an asynchronous communication model for three important IBE schemes; namely, Boneh and Franklin's IBE, Sakai and Kasahara's IBE, and Boneh and Boyen's BB1-IBE. We give special attention to the applicability of our protocols to all possible types of bilinear pairings and prove their IND-ID-CCA security in the random oracle model. Finally, we also perform a comparative analysis of these protocols and present recommendations for their use.

Note: This is an extended version of our paper appearing in 7th Conference on Security and Cryptography for Networks (SCN 2010).

Available format(s)
Public-key cryptography
Publication info
Published elsewhere. Unknown where it was published
Asynchronous communication modelIdentity-based encryption (IBE)Private-key generator (PKG)Distributed key generation (DKG)
Contact author(s)
akate @ cs uwaterloo ca
2010-07-23: last of 3 revisions
2009-07-21: received
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      author = {Aniket Kate and Ian Goldberg},
      title = {Asynchronous Distributed Private-Key Generators for Identity-Based Cryptography},
      howpublished = {Cryptology ePrint Archive, Paper 2009/355},
      year = {2009},
      note = {\url{}},
      url = {}
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