Welcome to the resource topic for 2023/668
Title:
Statement-Oblivious Threshold Witness Encryption
Authors: Sebastian Faust, Carmit Hazay, David Kretzler, Benjamin Schlosser
Abstract:The notion of witness encryption introduced by Garg et al. (STOC’13) allows to encrypt a message under a statement x from some NP-language \mathcal{L} with associated relation (x,w) \in \mathcal{R}, where decryption can be carried out with the corresponding witness w. Unfortunately, known constructions for general-purpose witness encryption rely on strong assumptions, and are mostly of theoretical interest. To address these shortcomings, Goyal et al. (PKC’22) recently introduced a blockchain-based alternative, where a committee decrypts ciphertexts when provided with a valid witness w. Blockchain-based committee solutions have recently gained broad interest to offer security against more powerful adversaries and construct new cryptographic primitives.
We follow this line of work, and propose a new notion of statement-oblivious threshold witness encryption. Our new notion offers the functionality of committee-based witness encryption while additionally hiding the statement used for encryption. We present two ways to build statement-oblivious threshold witness encryption, one generic transformation based on anonymous threshold identity-based encryption (A-TIBE) and one direct construction based on bilinear maps. Due to the lack of efficient A-TIBE schemes, the former mainly constitutes a feasibility result, while the latter yields a concretely efficient scheme.
ePrint: https://eprint.iacr.org/2023/668
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