International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Constant Ciphertext-Rate Non-Committing Encryption from Standard Assumptions

Zvika Brakerski
Pedro Branco
Nico Döttling
Sanjam Garg
Giulio Malavolta
Search ePrint
Search Google
Abstract: Non-committing encryption (NCE) is a type of public key encryption which comes with the ability to equivocate ciphertexts to encryptions of arbitrary messages, i.e., it allows one to find coins for key generation and encryption which ``explain'' a given ciphertext as an encryption of any message. NCE is the cornerstone to construct adaptively secure multiparty computation [Canetti et al. STOC'96] and can be seen as the quintessential notion of security for public key encryption to realize ideal communication channels. A large body of literature investigates what is the best message-to-ciphertext ratio (i.e., the rate) that one can hope to achieve for NCE. In this work we propose a near complete resolution to this question and we show how to construct NCE with constant rate in the plain model from a variety of assumptions, such as the hardness of the learning with errors (LWE), the decisional Diffie-Hellman (DDH), or the quadratic residuosity (QR) problem. Prior to our work, constructing NCE with constant rate required a trusted setup and indistinguishability obfuscation [Canetti et al. ASIACRYPT'17].
Video from TCC 2020
  title={Constant Ciphertext-Rate Non-Committing Encryption from Standard Assumptions},
  booktitle={Theory of Cryptography},
  author={Zvika Brakerski and Pedro Branco and Nico Döttling and Sanjam Garg and Giulio Malavolta},