Paper 2022/1532

Function-Hiding Decentralized Multi-Client Functional Encryption for Inner Products

Ky Nguyen, DIENS, École normale supérieure, CNRS, Inria, PSL University, Paris, France
David Pointcheval, DIENS, École normale supérieure, CNRS, Inria, PSL University, Paris, France
Robert Schädlich, DIENS, École normale supérieure, CNRS, Inria, PSL University, Paris, France
Abstract

Decentralized Multi-Client Functional Encryption (DMCFE) extends the basic functional encryption to multiple clients that do not trust each other. They can independently encrypt the multiple inputs to be given for evaluation to the function embedded in the functional decryption key. And they keep control on these functions as they all have to contribute to the generation of the functional decryption keys. As any encryption scheme, all the FE schemes provide privacy of the plaintexts. But the functions associated to the functional decryption keys might be sensitive too (e.g. a model in machine learning). The function-hiding property has thus been introduced to additionally protect the function evaluated during the decryption process. But it was not properly defined for previous definitions of DMCFE. In this paper, we provide a formal definition of DMCFE with complete function-hiding security game. We thereafter propose a concrete construction of function-hiding DMCFE for inner products, with strong security guarantees: the adversary is allowed to adaptively query multiple challenge ciphertexts and multiple challenge keys. Previous constructions were proven secure for a single challenge ciphertext only, in the selective setting (i.e. provided before the setup).

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Preprint.
Keywords
Functional Encryption Inner Product Function-Hiding
Contact author(s)
ky nguyen @ ens fr
david pointcheval @ ens fr
Robert Schaedlich @ ens fr
History
2022-11-07: approved
2022-11-05: received
See all versions
Short URL
https://ia.cr/2022/1532
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2022/1532,
      author = {Ky Nguyen and David Pointcheval and Robert Schädlich},
      title = {Function-Hiding Decentralized Multi-Client Functional Encryption for Inner Products},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1532},
      year = {2022},
      note = {\url{https://eprint.iacr.org/2022/1532}},
      url = {https://eprint.iacr.org/2022/1532}
}
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