We use the EasyCrypt proof assistant to formalize the adversarial approach to proving lower bounds for computational problems in the query model. This is done using a lower bound game between an algorithm and adversary, in which the adversary answers the algorithm’s queries in a way that makes the algorithm issue at least the desired number of queries. A complementary upper bound game is used for proving upper bounds of algorithms; here the adversary incrementally and adaptively realizes an algorithm’s input. We prove a natural connection between the lower and upper bound games, and apply our framework to three computational problems, including searching in an ordered list and comparison-based sorting, giving evidence for the generality of our notion of algorithm and the usefulness of our framework.
@InProceedings{stoughton_et_al:LIPIcs.ITP.2022.30, author = {Stoughton, Alley and Chen, Carol and Gaboardi, Marco and Qu, Weihao}, title = {{Formalizing Algorithmic Bounds in the Query Model in EasyCrypt}}, booktitle = {13th International Conference on Interactive Theorem Proving (ITP 2022)}, pages = {30:1--30:21}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-252-5}, ISSN = {1868-8969}, year = {2022}, volume = {237}, editor = {Andronick, June and de Moura, Leonardo}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2022.30}, URN = {urn:nbn:de:0030-drops-167399}, doi = {10.4230/LIPIcs.ITP.2022.30}, annote = {Keywords: query model, lower bound, upper bound, adversary argument, EasyCrypt} }
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