Paper 2023/668

Statement-Oblivious Threshold Witness Encryption

Sebastian Faust, Technical University of Darmstadt
Carmit Hazay, Bar-Ilan University
David Kretzler, Technical University of Darmstadt
Benjamin Schlosser, Technical University of Darmstadt

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.

Note: This is the full version of the paper of the same name published at CSF 2023.

Available format(s)
Public-key cryptography
Publication info
Published elsewhere. CSF 2023
Threshold Witness EncryptionStatement ObliviousnessCommittee-Based DecryptionThreshold Tag-Based Encryption
Contact author(s)
david kretzler @ tu-darmstadt de
benjamin schlosser @ tu-darmstadt de
2023-05-11: approved
2023-05-11: received
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Creative Commons Attribution


      author = {Sebastian Faust and Carmit Hazay and David Kretzler and Benjamin Schlosser},
      title = {Statement-Oblivious Threshold Witness Encryption},
      howpublished = {Cryptology ePrint Archive, Paper 2023/668},
      year = {2023},
      note = {\url{}},
      url = {}
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