Cryptology ePrint Archive: Report 2012/671

Fully Secure Unbounded Inner-Product and Attribute-Based Encryption

Tatsuaki Okamoto and Katsuyuki Takashima

Abstract: In this paper, we present the first inner-product encryption (IPE) schemes that are unbounded in the sense that the public parameters do not impose additional limitations on the predicates and attributes used for encryption and decryption keys. All previous IPE schemes were bounded, or have a bound on the size of predicates and attributes given public parameters fixed at setup. The proposed unbounded IPE schemes are fully (adaptively) secure and fully attribute-hiding in the standard model under a standard assumption, the decisional linear (DLIN) assumption. In our unbounded IPE schemes, the inner-product relation is generalized, where the two vectors of inner-product can be different sizes and it provides a great improvement of efficiency in many applications. We also present the first fully secure unbounded attribute-based encryption (ABE) schemes, and the security is proven under the DLIN assumption in the standard model. To achieve these results, we develop novel techniques, indexing and consistent randomness amplification, on the (extended) dual system encryption technique and the dual pairing vector spaces (DPVS).

Category / Keywords: public-key cryptography / functional encryption, attribute-based encryption, predicate encryption, unboundedness

Publication Info: This is a full version of a paper appearing in Asiacrypt 2012.

Date: received 27 Nov 2012

Contact author: Takashima Katsuyuki at aj MitsubishiElectric co jp

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Version: 20121128:174449 (All versions of this report)

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