,
Yunqi Li
,
Prashant Nalini Vasudevan
Creative Commons Attribution 4.0 International license
We study the implications of the existence of weak Zero-Knowledge (ZK) protocols for worst-case hard languages. These are protocols that have completeness, soundness, and zero-knowledge errors (denoted ε_c, ε_s, and ε_z, respectively) that might not be negligible. Under the assumption that there are worst-case hard languages in NP, we show the following:
1) If all languages in NP have NIZK proofs or arguments satisfying ε_c+ε_s+ε_z < 1, then One-Way Functions (OWFs) exist. This covers all possible non-trivial values for these error rates. It additionally implies that if all languages in NP have such NIZK proofs and ε_c is negligible, then they also have NIZK proofs where all errors are negligible. Previously, these results were known under the more restrictive condition ε_c+√{ε_s}+ε_z < 1 [Chakraborty et al., CRYPTO 2025].
2) If all languages in NP have k-round public-coin ZK proofs or arguments satisfying ε_c+ε_s+(2k-1)⋅ε_z < 1, then OWFs exist.
3) If, for some constant k, all languages in NP have k-round public-coin ZK proofs or arguments satisfying ε_c+ε_s+k⋅ε_z < 1, then infinitely-often OWFs exist.
@InProceedings{chatterjee_et_al:LIPIcs.ITC.2026.5,
author = {Chatterjee, Rohit and Li, Yunqi and Vasudevan, Prashant Nalini},
title = {{Weak Zero-Knowledge and One-Way Functions}},
booktitle = {7th Conference on Information-Theoretic Cryptography (ITC 2026)},
pages = {5:1--5:21},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-426-0},
ISSN = {1868-8969},
year = {2026},
volume = {385},
editor = {Dodis, Yevgeniy},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2026.5},
URN = {urn:nbn:de:0030-drops-270987},
doi = {10.4230/LIPIcs.ITC.2026.5},
annote = {Keywords: One-way functions, zero-knowledge}
}