Financially Backed Covert Security

Sebastian Faust, Carmit Hazay, David Kretzler, Benjamin Schlosser

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

3 Scopus citations


The security notion of covert security introduced by Aumann and Lindell (TCC’07) allows the adversary to successfully cheat and break security with a fixed probability 1 - ϵ, while with probability ϵ, honest parties detect the cheating attempt. Asharov and Orlandi (ASIACRYPT’12) extend covert security to enable parties to create publicly verifiable evidence about misbehavior that can be transferred to any third party. This notion is called publicly verifiable covert security (PVC) and has been investigated by multiple works. While these two notions work well in settings with known identities in which parties care about their reputation, they fall short in Internet-like settings where there are only digital identities that can provide some form of anonymity. In this work, we propose the notion of financially backed covert security (FBC), which ensures that the adversary is financially punished if cheating is detected. Next, we present three transformations that turn PVC protocols into FBC protocols. Our protocols provide highly efficient judging, thereby enabling practical judge implementations via smart contracts deployed on a blockchain. In particular, the judge only needs to non-interactively validate a single protocol message while previous PVC protocols required the judge to emulate the whole protocol. Furthermore, by allowing an interactive punishment procedure, we can reduce the amount of validation to a single program instruction, e.g., a gate in a circuit. An interactive punishment, additionally, enables us to create financially backed covert secure protocols without any form of common public transcript, a property that has not been achieved by prior PVC protocols.

Original languageEnglish
Title of host publicationPublic-Key Cryptography - PKC 2022 - 25th IACR International Conference on Practice and Theory of Public-Key Cryptography, Proceedings
EditorsGoichiro Hanaoka, Junji Shikata, Yohei Watanabe
PublisherSpringer Science and Business Media Deutschland GmbH
Number of pages31
ISBN (Print)9783030971304
StatePublished - 2022
Event25th IACR International Conference on Practice and Theory of Public-Key Cryptography, PKC 2022 - Virtual, Online
Duration: 8 Mar 202211 Mar 2022

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume13178 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference25th IACR International Conference on Practice and Theory of Public-Key Cryptography, PKC 2022
CityVirtual, Online

Bibliographical note

Publisher Copyright:
© 2022, International Association for Cryptologic Research.


  • Covert Security
  • Financial Punishment
  • Multi-Party Computation (MPC)
  • Public Verifiability


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