,
Uri Meir
,
Debanuj Nayak
,
Sofya Raskhodnikova
Creative Commons Attribution 4.0 International license
A central challenge in property testing is verifying algebraic structure with minimal access to data. A landmark result addressing this challenge, the linearity test of Blum, Luby, and Rubinfeld (JCSS `93), spurred a rich body of work on testing algebraic properties such as linearity and its generalizations to low-degree polynomials and group homomorphisms. However, classical tests for these properties assume unrestricted, noise-free access to the input function - an assumption that breaks down in adversarial or dynamic settings. To address this, Kalemaj, Raskhodnikova, and Varma (Theory of Computing `23) introduced the online manipulation model, where an adversary erases or corrupts query responses over time, based on the tester’s past queries. We initiate the study of manipulation-resilient testing for group homomorphism in this online model. Our main result is an optimal tester that makes O(1/ε+log t) queries, where ε is the distance parameter and t is the number of function values the adversary can erase or corrupt per query. Our result recovers the celebrated O(1/ε) bound by Ben-Or, Coppersmith, Luby, and Rubinfeld (Random Struct. Algorithms `08) for homomorphism testing in the standard property testing model, albeit with a different tester. Our tester, Random Signs Test, lifts known manipulation-resilient linearity testers for 𝔽₂ⁿ → 𝔽₂ to general group domains and codomains by introducing more randomness: instead of verifying the homomorphism condition for a sum of random elements, it uses additions and subtractions of random elements, randomly selecting a sign for each element. We also obtain improved group-specific query bounds for key families of groups. Our results show that despite the challenges of online manipulation, group homomorphism - a fundamental algebraic property - is efficiently testable across a wide range of domains and codomains. Finally, we formalize a general framework for proving online resilience.
@InProceedings{kelman_et_al:LIPIcs.APPROX/RANDOM.2026.58,
author = {Kelman, Esty and Meir, Uri and Nayak, Debanuj and Raskhodnikova, Sofya},
title = {{Homomorphism Testing with Resilience to Online Manipulations}},
booktitle = {Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2026)},
pages = {58:1--58:24},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-449-9},
ISSN = {1868-8969},
year = {2026},
volume = {392},
editor = {Singh, Mohit and Gur, Tom},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX/RANDOM.2026.58},
URN = {urn:nbn:de:0030-drops-277753},
doi = {10.4230/LIPIcs.APPROX/RANDOM.2026.58},
annote = {Keywords: Property Testing, Sublinear Algorithms, Online Manipulation Resilience, Group Theory}
}