Paper 2018/834

Identity-based Encryption Tightly Secure under Chosen-ciphertext Attacks

Dennis Hofheinz, Dingding Jia, and Jiaxin Pan


We propose the first identity-based encryption (IBE) scheme that is (almost) tightly secure against chosen-ciphertext attacks. Our scheme is efficient, in the sense that its ciphertext overhead is only seven group elements, three group elements more than that of the state-of-the-art passively (almost) tightly secure IBE scheme. Our scheme is secure in a multi-challenge setting, i.e., in face of an arbitrary number of challenge ciphertexts. The security of our scheme is based upon the standard symmetric external Diffie-Hellman assumption in pairing-friendly groups, but we also consider (less efficient) generalizations under weaker assumptions.

Note: add the omitted proofs in appendix, we aslo give two instatiations of the construction

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Publication info
Published by the IACR in ASIACRYPT 2018
identity-based encryptionchosen-ciphertext securitytight security reductions
Contact author(s)
dennis hofheinz @ kit edu
jiadingding @ iie ac cn
jiaxin pan @ kit edu
2018-11-30: revised
2018-09-06: received
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      author = {Dennis Hofheinz and Dingding Jia and Jiaxin Pan},
      title = {Identity-based Encryption Tightly Secure under Chosen-ciphertext Attacks},
      howpublished = {Cryptology ePrint Archive, Paper 2018/834},
      year = {2018},
      note = {\url{}},
      url = {}
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