[Resource Topic] 2024/264: Extractable Witness Encryption for KZG Commitments and Efficient Laconic OT

Welcome to the resource topic for 2024/264

Title:
Extractable Witness Encryption for KZG Commitments and Efficient Laconic OT

Authors: Nils Fleischhacker, Mathias Hall-Andersen, Mark Simkin

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.

ePrint: https://eprint.iacr.org/2024/264

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