Unbounded ABE via Bilinear Entropy Expansion, Revisited

Jie Chen (1) , Junqing Gong (2, 3) , Lucas Kowalczyk (4) , Hoeteck Wee (5, 6)

1 ECNU - East China Normal University [Shangaï]
2 ARIC - Arithmetic and Computing
3 LIP - Laboratoire de l'Informatique du Parallélisme
4 Columbia University [New York]
5 CASCADE - Construction and Analysis of Systems for Confidentiality and Authenticity of Data and Entities
6 PSL - Université Paris Sciences et Lettres

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.

Domaines: Informatique [cs]

Jie Chen, Junqing Gong, Lucas Kowalczyk, Hoeteck Wee. Unbounded ABE via Bilinear Entropy Expansion, Revisited. EUROCRYPT 2018 - Annual International Conference on the Theory and Applications of Cryptographic Techniques, Apr 2018, Tel Aviv, Israel. pp.503-534, ⟨10.1007/978-3-319-78381-9_19⟩. ⟨hal-01899901⟩