[Resource Topic] 2025/025: Chosen-Ciphertext Security for Inner Product FE: Mutli-Client and Multi-Input, Generically

Welcome to the resource topic for 2025/025

Title:
Chosen-Ciphertext Security for Inner Product FE: Mutli-Client and Multi-Input, Generically

Authors: Ky Nguyen

Abstract:

Functional Encryption is a powerful cryptographic primitive that allows for fine-grained access control over encrypted data. In the multi-user setting, especially Multi-Client and Multi-Input, a plethora of works have been proposed to study on concrete function classes, improving security, and more. However, the CCA-security for such schemes is still an open problem, where the only known works are on Public-Key Single-Client FE (Benhamouda, Bourse, and Lipmaa, PKC’17).
This work provides the first generic construction of CCA-secure Multi-Client FE for Inner Products, and Multi-Input FE for Inner Products, with instantiations from \mathsf{SXDH} and \mathsf{DLIN} for the former, and \mathsf{DDH} or \mathsf{DCR} for the latter. Surprisingly, in the case of secret key MIFE we attain the same efficiency as in the public key single-client setting. In the MCFE setting, a toolkit of CCA-bootstrapping techniques is developed to achieve CCA-security in its \mathit{secret~key} setting.

ePrint: https://eprint.iacr.org/2025/025

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