Title | On the Impossibility of Post-Quantum Black-Box Zero-Knowledge in Constant Rounds |

Publication Type | Journal Article |

Year of Publication | 2021 |

Authors | Chia, N-H, Chung, K-M, Liu, Q, Yamakawa, T |

Date Published | 3/20/2021 |

Abstract | We investigate the existence of constant-round post-quantum black-box zero-knowledge protocols for NP. As a main result, we show that there is no constant-round post-quantum black-box zero-knowledge argument for NP unless NP⊆BQP. As constant-round black-box zero-knowledge arguments for NP exist in the classical setting, our main result points out a fundamental difference between post-quantum and classical zero-knowledge protocols. Combining previous results, we conclude that unless NP⊆BQP, constant-round post-quantum zero-knowledge protocols for NP exist if and only if we use non-black-box techniques or relax certain security requirements such as relaxing standard zero-knowledge to ϵ-zero-knowledge. Additionally, we also prove that three-round and public-coin constant-round post-quantum black-box ϵ-zero-knowledge arguments for NP do not exist unless NP⊆BQP. |

URL | https://arxiv.org/abs/2103.11244 |