Cryptology ePrint Archive: Report 2020/197

Dynamic Decentralized Functional Encryption

Jérémy Chotard and Edouard Dufour-Sans and Romain Gay and Duong Hieu Phan and David Pointcheval

Abstract: We introduce Dynamic Decentralized Functional Encryption (DDFE), a generalization of Functional Encryption which allows multiple users to join the system dynamically, without relying on a trusted third party or on expensive and interactive Multi-Party Computation protocols. This notion subsumes existing multi-user extensions of Functional Encryption, such as Multi-Input, Multi-Client, and Ad Hoc Multi-Input Functional Encryption. We define and construct schemes for various functionalities which serve as building-blocks for latter primitives and may be useful in their own right, such as a scheme for dynamically computing sums in any Abelian group. These constructions build upon simple primitives in a modular way, and have instantiations from well-studied assumptions, such as DDH or LWE. Our constructions culminate in an Inner-Product scheme for computing weighted sums on aggregated encrypted data, from standard assumptions in prime-order groups in the Random Oracle Model.

Category / Keywords: public-key cryptography / Dynamic, Decentralized, Functional Encryption, Inner Product.

Original Publication (with minor differences): IACR-CRYPTO-2020

Date: received 16 Feb 2020, last revised 6 Sep 2020

Contact author: e dufoursans at gmail com,romain rgay@gmail com,david pointcheval@ens fr

Available format(s): PDF | BibTeX Citation

Version: 20200906:211801 (All versions of this report)

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