Paper 2007/100

Practical Identity-Based Encryption (IBE) in Multiple PKG Environments and Its Applications

Shengbao Wang and Zhenfu Cao


Identity-based encryption (IBE) schemes are usually used in multiple-PKG environments --- on the one hand, each administrative domain (e.g., a relatively small and close organization) maintains its own private key generator (PKG); on the other hand, encryption across domains becomes a prevalent requirement. In this paper, we present a new IBE scheme using bilinear pairings. Compared with the famous IBE scheme of Boneh and Franklin, we show that ours is more practical in the multiple-PKG environment. We prove that our scheme meets chosen ciphertext security in the random oracle model, assuming the intractability of the standard Bilinear Diffie-Hellman (BDH) problem. As an application of our IBE scheme, we also propose an escrowed ElGamal scheme which possesses certain good properties in practice.

Note: Thanks to a novel technique for simulating the H_1 oracle (due to Lal and Sharma, on page 6 of [LS07], which is adapted in our proof for Lemma 2) the IND-ID-CCA security of the full M-IBE scheme is now reduced to the standard BDH problem.

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Published elsewhere. In submission
identity-based encryption (IBE)multiple-PKG environmentspublic key encryption (PKE)escrowed ElGamalbilinear pairings
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shengbaowang @ gmail com
2007-11-26: last of 2 revisions
2007-03-22: received
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      author = {Shengbao Wang and Zhenfu Cao},
      title = {Practical Identity-Based Encryption (IBE) in Multiple PKG Environments and Its Applications},
      howpublished = {Cryptology ePrint Archive, Paper 2007/100},
      year = {2007},
      note = {\url{}},
      url = {}
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