Paper 2018/116

Unbounded ABE via Bilinear Entropy Expansion, Revisited

Jie Chen, Junqing Gong, Lucas Kowalczyk, and Hoeteck Wee


We present simpler and improved constructions of unbounded attribute-based encryption (ABE) schemes with constant-size public parameters under static assumptions in bilinear groups. Concretely, we obtain: - a simple and adaptively secure unbounded ABE scheme in composite-order groups, improving upon a previous construction of Lewko and Waters (Eurocrypt '11) which only achieves selective security; - an improved adaptively secure unbounded ABE scheme based on the $k$-linear assumption in prime-order groups with shorter ciphertexts and secret keys than those of Okamoto and Takashima (Asiacrypt '12); - the first adaptively secure unbounded ABE scheme for arithmetic branching programs under static assumptions. At the core of all of these constructions is a "bilinear entropy expansion" lemma that allows us to generate any polynomial amount of entropy starting from constant-size public parameters; the entropy can then be used to transform existing adaptively secure "bounded" ABE schemes into unbounded ones.

Available format(s)
Public-key cryptography
Publication info
A major revision of an IACR publication in EUROCRYPT 2018
attribute-based encryption
Contact author(s)
junqing gong @ ens-lyon fr
2018-01-31: received
Short URL
Creative Commons Attribution


      author = {Jie Chen and Junqing Gong and Lucas Kowalczyk and Hoeteck Wee},
      title = {Unbounded ABE via Bilinear Entropy Expansion, Revisited},
      howpublished = {Cryptology ePrint Archive, Paper 2018/116},
      year = {2018},
      note = {\url{}},
      url = {}
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