Decentralized Multi-Client Functional Encryption for Inner Product

Jérémy Chotard (1, 2, 3, 4) , Edouard Dufour Sans (1, 2, 4) , Romain Gay (1, 2, 4) , David Pointcheval (1, 2, 4) , Duong Hieu Phan (3)

1 CASCADE - Construction and Analysis of Systems for Confidentiality and Authenticity of Data and Entities
2 DI-ENS - Département d'informatique - ENS Paris
3 XLIM-MATHIS - Mathématiques & Sécurité de l'information
4 PSL - Université Paris sciences et lettres

We consider a situation where multiple parties, owning data that have to be frequently updated, agree to share weighted sums of these data with some aggregator, but where they do not wish to reveal their individual data, and do not trust each other. We combine techniques from Private Stream Aggregation (PSA) and Functional Encryption (FE), to introduce a primitive we call Decentralized Multi-Client Functional Encryption (DMCFE), for which we give a practical instantiation for Inner Product functionalities. This primitive allows various senders to \emph{non-interactively} generate ciphertexts which support inner-product evaluation, with functional decryption keys that can also be generated \emph{non-interactively}, in a distributed way, among the senders. Interactions are required during the setup phase only. We prove adaptive security of our constructions, while allowing corruptions of the clients, in the random oracle model.

Mots clés: Functional Encryption; Multi-Client; Decentralized; Function-Hiding; Inner Product

Domaines: Cryptographie et sécurité [cs.CR]

Jérémy Chotard, Edouard Dufour Sans, Romain Gay, David Pointcheval, Duong Hieu Phan. Decentralized Multi-Client Functional Encryption for Inner Product. ASIACRYPT '18 - 24th Annual International Conference on the Theory and Application of Cryptology and Information Security, Dec 2018, Brisbane, Australia. ⟨10.1007/978-3-030-03329-3_24⟩. ⟨hal-01668020⟩