In this work, we reexamine the vulnerability of Payment Channel Networks (PCNs) to bribing attacks, where an adversary incentivizes blockchain miners to deliberately ignore a specific transaction to undermine the punishment mechanism of PCNs. While previous studies have posited a prohibitive cost for such attacks, we show that this cost can be dramatically reduced (to approximately $125), thereby increasing the likelihood of these attacks. To this end, we introduce Bribe & Fork, a modified bribing attack that leverages the threat of a so-called feather fork which we analyze with a novel formal model for the mining game with forking. We empirically analyze historical data of some real-world blockchain implementations to evaluate the scale of this cost reduction. Our findings shed more light on the potential vulnerability of PCNs and highlight the need for robust solutions.
@InProceedings{avarikioti_et_al:LIPIcs.AFT.2024.11, author = {Avarikioti, Zeta and K\k{e}dzior, Pawe{\l} and Lizurej, Tomasz and Michalak, Tomasz}, title = {{Bribe \& Fork: Cheap PCN Bribing Attacks via Forking Threat}}, booktitle = {6th Conference on Advances in Financial Technologies (AFT 2024)}, pages = {11:1--11:22}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-345-4}, ISSN = {1868-8969}, year = {2024}, volume = {316}, editor = {B\"{o}hme, Rainer and Kiffer, Lucianna}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2024.11}, URN = {urn:nbn:de:0030-drops-209473}, doi = {10.4230/LIPIcs.AFT.2024.11}, annote = {Keywords: Blockchain, Payment Channels Networks, Timelock Bribing, Feather Forking} }
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