Statement-Oblivious Threshold Witness Encryption

Sebastian Faust; Carmit Hazay; David Kretzler; Benjamin Schlosser

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

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 $L$ with associated relation , where decryption can be carried out with the corresponding witness . 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.

Metadata

Available format(s): PDF
Category: Public-key cryptography
Publication info: Published elsewhere. CSF 2023
Keywords: Threshold Witness Encryption Statement Obliviousness Committee-Based Decryption Threshold Tag-Based Encryption
Contact author(s): david kretzler @ tu-darmstadt de
benjamin schlosser @ tu-darmstadt de
History: 2023-05-11: approved; 2023-05-11: received; See all versions
Short URL: https://ia.cr/2023/668
License: CC BY

BibTeX

@misc{cryptoeprint:2023/668,
      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},
      url = {https://eprint.iacr.org/2023/668}
}