- Title: Unbounded ABE via Bilinear Entropy Expansion, Revisited
- Venue: SEIEE 3-404
- Time: 2:00-3:00PM, March 5, 2019
- Speaker: Dr. Junqing Gong
- Affiliation: École Normale Supérieure
This talk presents simpler and improved constructions of unbounded attribute-based encryption (ABE) schemes with constant-size public parameters under static assumptions in bilinear groups. Concretely, we show:
- 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.
Based on joint work with Jie Chen, Lucas Kowalczyk, Hoeteck Wee.
Junqing Gong is a postdoc researcher of CNRS, ENS and PSL. Before that, he was a postdoc researcher at ENS de Lyon. He obtained his Ph.D. from Shanghai Jiao Tong University in 2016. His research interest is public-key cryptography, in particular, design and analysis of practical functional encryptions.