Vassilis Zikas

Purdue University
Computer Science Department

email: vzikas cs.purdue.edu  


My research interests include:

  • Cryptography
  • Computer Security
  • Blockchain Technologies
  • Cryptocurrencies
  • Game Theory
  • Distributed Computing

Latest news:
  • Our paper on how to circumvent limitation of the mediated model was accepted to CSF 2022.
  • Excited to have our paper on do's and don'ts when using a global (ledger) functionality accepted at TCC 2021.
  • Tune in for my invited talk at the Workshop on Distributed Ledger and Economics.
  • Excited about our paper on rational-crypto analysis of 51% attacks that was accepted at CRYPTO 2021.
  • Our paper on blockchain-based synchronizers was accepted at EUROCRYPT 2021.


Professional Activities


Teaching and Advising


Publications

Michele Ciampi, Yun Lu, and Vassilis Zikas
Collusion-Preserving Computation without a Mediator
IEEE Computer Security Foundations Symposium —CSF 2022 (to appear).
A preliminary full version is available here: [ PDF ]


Christian Badertscher, Yun Lu, and Vassilis Zikas
A Rational Protocol Treatment of 51% Attacks
Advances in Cryptology — CRYPTO 2021 (to appear).
A preliminary full version is available here: [ PDF ]


Christian Badertscher, Peter Gazi, Aggelos Kiayias, Alexander Russell, and Vassilis Zikas
Dynamic Ad Hoc Clock Synchronization via Proof of Stake
Advances in Cryptology — EUROCRYPT 2021 (to appear).
A preliminary full version is available here: [ PDF ]


Christian Badertscher, Julia Hesse, and Vassilis Zikas
On the (Ir)Replaceability of Global Setups, or How (Not) to Use a Global Ledger
Theory of Cryptography Conference — TCC 2021, (to appear).
A preliminary full version is available here: [ PDF ]


Christian Badertscher, Ran Canetti, Julia Hesse, Björn Tackmann, and Vassilis Zikas
Universal Composition with Global Subroutines: Capturing Global Setup within Plain UC
Theory of Cryptography Conference — TCC 2020, LNCS, Springer, vol 12552, pp 1–30, 2020.
A preliminary full version is available here: [ PDF ]


Ao Liu, Yun Lu, Lirong Xia, and Vassilis Zikas
How Private Is Your Voting? A Framework for Comparing the Privacy of Voting Mechanisms
Uncertainty in Artificial Intelligence — UAI 2020, AUAI Press, PMLR vol 124, 2020. Preliminary version appeared at WADE 2018.
A preliminary full version is available here: [ PDF ]


Ran Cohen, Juan Garay, and Vassilis Zikas
Broadcast-Optimal Two-Round MPC
Advances in Cryptology — EUROCRYPT 2020, LNCS, Springer, vol 12106, pp 428–858, 2020.
A preliminary full version is available here: [ PDF ]


Juan Garay, Aggelos Kiayias, Rafail Ostrovsky, Giorgos Panagiotakos, and Vassilis Zikas
Resource-Restricted Cryptography: Revisiting MPC Bounds in the Proof-of-Work Era
Advances in Cryptology — EUROCRYPT 2020, LNCS, Springer, vol 12106, pp 129–158, 2020.

A preliminary full version is available here: [ PDF ]


Michele Ciampi, Aydin Kheirbakhsh Abadi, Aggelos Kiayias, and Vassilis Zikas
Timed Signatures and Zero-Knowledge Proofs: Timestamping in the Blockchain Era
Applied Cryptography and Network Security — ACNS 2020, LNCS, Springer, vol 12146, pp 335–354, 2020.
A preliminary full version is available here: [ PDF ]


Leonard Kleinrock, Rafail Ostrovsky, and Vassilis Zikas
Proof-of-Reputation Blockchain with Nakamoto Fallback
INDOCRYPT 2020 (to appear).
A preliminary full version is available here: [ PDF ]


Muhammad Ishaq, Ana Milanova, and Vassilis Zikas
Efficient MPC via Program Analysis: A Framework for Efficient Optimal Mixing
ACM Conference on Computer and Communications Security — CCS 2019, ACM, pp 1539–1556, 2019.
A preliminary full version is available here: [ PDF ]


Thomas Kerber, Markulf Kohlweiss, Aggelos Kiayias, and Vassilis Zikas
Ouroboros Crypsinous: Privacy-Preserving Proof-of-Stake
IEEE Symposium on Security and Privacy — S&P 2019, IEEE, pp 157–174, 2019.
A preliminary full version is available here: [ PDF ]


Maksim Tsikhanovich, Malik Magdon-Ismail, Muhammad Ishaq, and Vassilis Zikas
PD-ML-Lite: Private Distributed Machine Learning from Lightweight Cryptography

Information Security Conference ISC 2019, LNCS, Springer, vol 11723, pp 149–167, 2019..
A preliminary full version is available here: [ PDF ]


Christian Badertscher, Peter Gazi, Aggelos Kiayias, Alexander Russell, and Vassilis Zikas
Ouroboros Genesis: Composable Proof-of-Stake Blockchains with Dynamic Availability
ACM Conference on Computer and Communications Security — CCS 2018, ACM, pp. 913–930, 2018.
A preliminary full version is available here: [ PDF ]

Ran Gelles, Anat Paskin-Cherniavsky, and Vassilis Zikas
Secure Two-Party Computation over Unreliable Channels
Security and Cryptography for Networks — SCN 2018, LNCS, Springer, vol 11035, pp 445–463, 2018.
A preliminary full version is available here: [ PDF ]

Christian Badertscher, Juan Garay, Ueli Maurer, Daniel Tschudi, and Vassilis Zikas
But Why does it Work? A Rational Protocol Design Treatment of Bitcoin
Advances in Cryptology — EUROCRYPT 2018, LNCS, Springer, vol 10821, pp 445–463, 2018.
A preliminary full version is available here: [ PDF ]

Christian Badertscher, Daniel Tschudi, Ueli Maurer, and Vassilis Zikas
Bitcoin as a Transaction Ledger: A Composable Treatment
Advances in Cryptology — CRYPTO 2017, LNCS, Springer, vol 10401, pp 324–356, 2017.
A preliminary full version is available here: [ PDF ]

Juan Garay, Yuval Ishai, Rafail Ostrovsky, and Vassilis Zikas
The Price of Low Communication in Secure Multi-Party Computation
Advances in Cryptology — CRYPTO 2017, Lecture Notes in Computer Science, Springer, vol 10401, pp 420–446, 2017.
A preliminary full version is available here: [ PDF ]

Ran Cohen, Sandro Coretti, Juan Garay, and Vassilis Zikas
Round-Preserving Parallel Composition of Probabilistic-Termination Protocols
International Colloquium on Automata, Languages and Programming — ICALP 2017, Leibniz Intl. Proc. in Informatics, pp. 37:1–37:15, 2017.
A preliminary full version is available here: [ PDF ]

Sandro Coretti, Juan Garay, Martin Hirt, and Vassilis Zikas
Constant-Round Asynchronous Multi-Party Computation
Advances in Cryptology — ASIACRYPT 2016, LNCS, Springer, vol 10032, pp 998–1021, 2016.
A preliminary full version is available here: [ PDF ]

Martin Hirt, Ueli Maurer, Daniel Tschudi, and Vassilis Zikas
Network-Hiding Communication and Applications to Multi-Party Protocols
Advances in Cryptology — CRYPTO 2016, LNCS, Springer, vol 9816, pp 335–365, 2016.
A preliminary full version is available here: [ PDF ]

Ran Cohen, Sandro Coretti, Juan Garay, and Vassilis Zikas
Probabilistic Termination and Composability of Cryptographic Protocols
Advances in Cryptology — CRYPTO 2016, LNCS, Springer, vol 9816, pp 240–269, 2016.
A preliminary full version is available here: [ PDF ]

Aggelos Kiayias, Hong-Sheng Zhou, and Vassilis Zikas
Fair and Robust Multi-Party Computation using a Global Transaction Ledger
Advances in Cryptology — EUROCRYPT 2016, LNCS, Springer, vol 9666, pp 281–290, 2016.
A preliminary full version is available here: [ PDF ]

Richard J. Lipton, Rafail Ostrovsky, and Vassilis Zikas
Provably Secure Virus Detection: Using The Observer Effect Against Malware
International Colloquium on Automata, Languages and Programming — ICALP 2016, Leibniz Intl. Proc. in Informatics, pp. 32:1–32:14, 2016.

Juan Garay, Bjoern Tackmann, and Vassilis Zikas
Fair Distributed Computation of Reactive Functions
International Symposium on Distributed Computing — DISC 2015, pp 497–512, 2015.
A preliminary full version is available here: [ PDF ]

Joël Alwen, Rafail Ostrovsky, Hong-Sheng Zhou, and Vassilis Zikas
Incoercible Multi-Party Computation and Universally Composable Receipt-Free Voting
Advances in Cryptology — CRYPTO 2015, LNCS, Springer, vol 9216, pp 763–780, 2015.

Juan Garay, Jonathan Katz, Bjoern Tackmann, and Vassilis Zikas
How Fair is Your Protocol? A Utility-based Approach to Protocol Optimality
ACM Symposium on Principles of Distributed Computing — PODC 2015, pp 281–290, 2015.
A preliminary full version is available here: [ PDF ]

Nishanth Chandran, Wutichai Chongchitmate, Juan A. Garay, Shafi Goldwasser, Rafail Ostrovsky, and Vassilis Zikas
The Hidden Communication Graph Model: 
Achieving Communication Locality and Optimal Resilience in the Presence of Adaptive Faults

Innovations in Theoretical Computer Science — ITCS 2015, pp 153–162, 2015.
A preliminary full version is available here: [ PDF ]


Yuval Ishai, Rafail Ostrovsky, and Vassilis Zikas
Secure Multi-Party Computation with Identifiable Abort
Advances in Cryptology — CRYPTO 2014, LNCS, Springer, vol 8617, pp 369–386, 2014.
A preliminary full version is available here: [ PDF ]

Seung Geol Choi, Jonathan Katz, Alex J. Malozemoff, and Vassilis Zikas
Efficient Three-Party Computation from Cut-and-Choose
Advances in Cryptology — CRYPTO 2014, LNCS, Springer, vol 8617, pp 513–530, 2014.
A preliminary full version is available here: [ PDF ]

Jonathan Katz, Aggelos Kiayias, Hong-Sheng Zhou, and Vassilis Zikas
Distributing the Setup in Universally Composable Secure Multi-Party Computation
ACM Symposium on Principles of Distributed Computing – PODC 2014, pp 20–29, 2014.

Juan Garay, Jonathan Katz, Ueli Maurer, Bjoern Tackmann, and Vassilis Zikas
Rational Protocol Design: Cryptography Against Incentive-Driven Adversaries
IEEE Symposium on Foundations of Computer Science — FOCS 2013, pp 648–657, 2013.
A preliminary full version is available here: [ PDF ]

Jonathan Katz, Ueli Maurer, Bjoern Tackmann, and Vassilis Zikas
Universally Composable Synchronous Computation
Theory of Cryptography Conference — TCC 2013, LNCS, Springer, vol 7785, pp 477–498, 2013.
A preliminary full version is available here: [ PDF ]

Jonathan Katz, Serge Fehr, Fang Song, Hong-Sheng Zhou, and Vassilis Zikas
Feasibility and Completeness of Cryptographic Tasks in the Quantum World
Theory of Cryptography Conference — TCC 2013, LNCS, Springer-Verlag, vol 7785, pp 281-296, 2013.
An extended abstract of this work was also presented at ICITS 2012, workshop track.

Joël Alwen, Jonathan Katz, Ueli Maurer, and Vassilis Zikas
Collusion-Preserving Computation
Advances in Cryptology — CRYPTO 2012, LNCS, Springer, vol 7417, pp 124-143, 2012.
A preliminary full version is available here: [ PDF ]

Adam Groce, Jonathan Katz, Aishwarya Thiruvengadam, and Vassilis Zikas
Byzantine Agreement with a Rational Adversary
International Colloquium on Automata, Languages and Programming — ICALP 2012, LNCS, Springer, vol. 7392, pp. 561–572, 2012.
Available files: [ PDF ]

Martin Hirt and Vassilis Zikas
Player-Centric Byzantine Agreement
International Colloquium on Automata, Languages and Programming — ICALP 2011, LNCS, Springer, vol. 6755, pp. 281–292, 2011.
Available files: [ PDF ]

Martin Hirt and Vassilis Zikas
Adaptively Secure Broadcast
Advances in Cryptology — EUROCRYPT 2010, LNCS, Springer, vol. 6110, pp. 466–485, 2010.
Available files: [ PDF ]

Sarah Hauser, Ueli Maurer, and Vassilis Zikas
Realistic Failures in Secure Multi-party Computation
Theory of Cryptography Conference — TCC 2009, LNCS, Springer, vol. 5444, pp. 274-293, 2009.
Available files: [ PDF ]

Martin Hirt, Ueli Maurer, and Vassilis Zikas
MPC vs. SFE: Unconditional and Computational Security
Advances in Cryptology — ASIACRYPT 2008, LNCS, Springer, vol. 5350, pp. 1–18, 2008.
Available files: [ PDF ]

Zuzana Beerliova-Trubiniova, Matthias Fitzi, Martin Hirt, Ueli Maurer, and Vassilis Zikas
MPC vs. SFE: Perfect Security in a Unified Corruption Model
Theory of Cryptography Conference — TCC 2008, LNCS, Springer, vol. 4948, pp. 231–250, 2008.
Available files: [ PDF ]

Journals, Posters, Pre-prints, and Manuscripts 


Christian Badertscher, Peter Gazi, Aggelos Kiayias, Alexander Russell, and Vassilis Zikas
Consensus Redux: Distributed Ledgers in the Face of Adversarial Supremacy
Manuscript.


Michele Ciampi, Rafail Ostrovsky, Hendrik Waldner, and Vassilis Zikas
Round-Optimal and Communication-Efficient Multiparty Computation
Manuscript.
A preliminary full version is available here: [ PDF ]


Ran Cohen, Sandro Coretti, Juan A. Garay, and Vassilis Zikas
Round-Preserving Parallel Composition of Probabilistic-Termination Cryptographic Protocols
Journal of Cryptology 34(2): 12, 2021


Ran Cohen, Sandro Coretti, Juan A. Garay, and Vassilis Zikas
Probabilistic Termination and Composability of Cryptographic Protocols
Journal of Cryptology 32(3): 690-741, 2019


Kai-Min Chung, Marios Georgiou, Ching-Yi Lai, and Vassilis Zikas
Cryptography with Disposable Backdoors

Special Issue on Quantum Cryptography and Cyber Security, Cryptography 2019, 3(3), 22; https://doi.org/10.3390/cryptography3030022.
A preliminary full version is available here: [ PDF ]


Yun Lu, Konstantinos Mitropoulos, Rafail Ostrovsky, Avraham Weinstock, and Vassilis Zikas
Cryptographically Secure Detection of Injection Attacks
ACM CCS 2018 (poster).

Books


Secure Multi-Party Computation (invited chapter)
Editors: Manoj Prabhakaran and Amit Sahai
Cryptology and Information Security Series, vol.10, IOS Press, Amsterdam, ISBN 978-1-61499-168-7, 2012.

Generalized Corruption Models in Secure Multi-Party Computation (PhD thesis)
ETH Series in Information Security and Cryptography, Hartung-Gorre Verlag, ISBN 3-86628-338-5, 2010.