Cryptology ePrint Archive: Report 2018/116

Unbounded ABE via Bilinear Entropy Expansion, Revisited

Jie Chen and Junqing Gong and Lucas Kowalczyk and Hoeteck Wee

Abstract: 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.

Category / Keywords: public-key cryptography / attribute-based encryption

Original Publication (with major differences): IACR-EUROCRYPT-2018

Date: received 31 Jan 2018, last revised 31 Jan 2018

Contact author: junqing gong at ens-lyon fr

Available format(s): PDF | BibTeX Citation

Version: 20180131:202538 (All versions of this report)

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