Sliding Window Challenge Process for Congestion Detection

Ayelet Lotem*, Sarah Azouvi, Patrick McCorry, Aviv Zohar

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


Many prominent smart contract applications such as payment channels, auctions, and voting systems often involve a mechanism in which some party must respond to a challenge or appeal some action within a fixed time limit. This pattern of challenge-response mechanisms poses great risks if, during periods of high transaction volume, the network becomes congested. In this case, fee market competition can prevent the inclusion of the response in blocks, causing great harm. As a result, responders are allowed long periods to submit their response and overpay in fees. To overcome these problems and improve challenge-response protocols, we suggest a secure mechanism that detects congestion in blocks and adjusts the deadline of the response accordingly. The responder is thus guaranteed a deadline extension should congestion arise. We lay theoretical foundations for congestion signals in blockchains and then proceed to analyze and discuss possible attacks on the mechanism and evaluate its robustness. Our results show that in Ethereum, using short response deadlines as low as 3 h, the protocol has >99% defense rate from attacks even by miners with up to 33 % of the computational power. Using shorter deadlines such as one hour is also possible with a similar defense rate for attackers with up to 27 % of the power.

Original languageAmerican English
Title of host publicationFinancial Cryptography and Data Security - 26th International Conference, FC 2022, Revised Selected Papers
EditorsIttay Eyal, Juan Garay
PublisherSpringer Science and Business Media Deutschland GmbH
Number of pages19
ISBN (Print)9783031182822
StatePublished - 2022
Event26th International Conference on Financial Cryptography and Data Security, FC 2022 - Saint George, Grenada
Duration: 2 May 20226 May 2022

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume13411 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference26th International Conference on Financial Cryptography and Data Security, FC 2022
CitySaint George

Bibliographical note

Publisher Copyright:
© 2022, International Financial Cryptography Association.


  • Challenge-response
  • Congestion


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