International Association for Cryptologic Research

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Extractable Witness Encryption for KZG Commitments and Efficient Laconic OT

Authors:
Nils Fleischhacker , Ruhr University Bochum
Mathias Hall-Andersen , ZkSecurity
Mark Simkin , Independent Researcher
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Presentation: Slides
Conference: ASIACRYPT 2024
Abstract: We present a concretely efficient and simple extractable witness encryption scheme for KZG polynomial commitments. It allows to encrypt a message towards a triple $(\mathsf{com}, \alpha, \beta)$, where $\mathsf{com}$ is a KZG commitment for some polynomial $f$. Anyone with an opening for the commitment attesting $f(\alpha) = \beta$ can decrypt, but without knowledge of a valid opening the message is computationally hidden. Our construction is simple and highly efficient. The ciphertext is only a single group element. Encryption and decryption both require a single pairing evaluation and a constant number of group operations. Using our witness encryption scheme, we construct a simple and highly efficient laconic OT protocol, which significantly outperforms the state of the art in most important metrics.
BibTeX
@inproceedings{asiacrypt-2024-34799,
  title={Extractable Witness Encryption for KZG Commitments and Efficient Laconic OT},
  publisher={Springer-Verlag},
  author={Nils Fleischhacker and Mathias Hall-Andersen and Mark Simkin},
  year=2024
}