Paper 2019/058

Tightly secure hierarchical identity-based encryption

Roman Langrehr and Jiaxin Pan


We construct the first tightly secure hierarchical identity-based encryption (HIBE) scheme based on standard assumptions, which solves an open problem from Blazy, Kiltz, and Pan (CRYPTO 2014). At the core of our constructions is a novel randomization technique that enables us to randomize user secret keys for identities with flexible length. The security reductions of previous HIBEs lose at least a factor of Q, which is the number of user secret key queries. Different to that, the security loss of our schemes is only dependent on the security parameter. Our schemes are adaptively secure based on the Matrix Diffie-Hellman assumption, which is a generalization of standard Diffie-Hellman assumptions such as k-Linear. We have two tightly secure constructions, one with constant ciphertext size, and the other with tighter security at the cost of linear ciphertext size. Among other things, our schemes imply the first tightly secure identity-based signature scheme by a variant of the Naor transformation.

Available format(s)
Public-key cryptography
Publication info
A major revision of an IACR publication in PKC 2019
hierarchical identity-based encryptiontight securityaffine message authentication codes
Contact author(s)
roman langrehr @ inf ethz ch
jiaxin pan @ ntnu no
2020-02-27: last of 2 revisions
2019-01-25: received
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      author = {Roman Langrehr and Jiaxin Pan},
      title = {Tightly secure hierarchical identity-based encryption},
      howpublished = {Cryptology ePrint Archive, Paper 2019/058},
      year = {2019},
      note = {\url{}},
      url = {}
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