Cryptology ePrint Archive: Report 2013/638

DFA-Based Functional Encryption: Adaptive Security from Dual System Encryption

Somindu C. Ramanna

Abstract: We present an adaptively secure functional encryption (FE) scheme based on deterministic finite automata (DFA). The construction uses composite-order bilinear pairings and is built upon the selectively secure DFA-based FE scheme of Waters (Crypto 2012). The scheme is proven secure using the dual system methodology under static subgroup decision assumptions. A dual system proof requires generating of semi-functional components from the instance. In addition, these components must be shown to be properly distributed in an attacker's view. This can be ensured by imposing a restriction on the automata and strings over which the scheme is built i.e., every symbol can appear at most once in a string and in the set of transition tuples of an automata. First a basic construction with the restrictions is obtained and proved to be adaptively secure. We then show how to extend this basic scheme to a full scheme where the restrictions can be relaxed by placing a bound on the number of occurrences of any symbol in a string and in the set of transitions. With the relaxed restrictions, our system supports functionality defined by a larger class of regular languages.

Category / Keywords: functional encryption (FE), deterministic finite automata, FE over regular languages, dual system encryption

Date: received 5 Oct 2013

Contact author: somindu_r at isical ac in

Available format(s): PDF | BibTeX Citation

Version: 20131005:134757 (All versions of this report)

Short URL: ia.cr/2013/638

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