Vassilis Zikas

Vassilis Zikas

Georgia Tech
School of Cybersecurity and Privacy
School of Computer Science (by courtesy)
CODA S0919
Atlanta, GA 30308

email: vzikas gatech.edu  


My research interests include:

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

I am looking for motivated PhD students with interest in cryptography, blockchain technologies, security, and/or fault-tolerant distributed computing. If you are already a student at Purdue send me an email. Otherwise, if you are interested in working with me please apply through the official Georgia Tech process and make sure you include the above areas and my name in your application.
Latest news:
  • Excited to have three papers accepted at TCC 2024.
  • Our paper on blockchain security against adversaries with temporary majority control of the underlying resourse was accepted at CSF 2024.
  • Our paper on adaptor sibnagures was accepted at ASIACRYPT 2024.
  • Our paper on black-box differential privacy estimators was accepted at S&P 2024.
  • Excited and honored to be awarded an AnlytiXIN Fellowship!
  • Our paper on concurrent round-preserving composition of asynchronous Byzantine agreement was accepted at TCC 2023.
  • Excited to have my paper on MPC optimization via vectorization accepted at ACM CCS 2023.
  • The blockchain lab had two papers accepted at CRYPTO 2023.
  • Proud to be the recepient of the 2023 Leadership Award from the Purdue College of Science

Professional Activities

Teaching and Advising

Publications

Nishanth Chandran, Juan Garay, Ankit Misra, Rafail Ostrovsky, and Vassilis Zikas
Adaptive Security, Erasures, and Network Assumptions in Communication-Local MPC
Theory of Cryptography Conference — TCC 2024 (to appear).
A preliminary full version is available here: [ PDF ]

Jaspal Singh, Yu Wei, and Vassilis Zikas
Information-Theoretic Multi-Server Private Information Retrieval with Client Preprocessing
Theory of Cryptography Conference — TCC 2024 (to appear).
A preliminary full version is available here: [ PDF ]

Konstantinos Brazitikos and Vassilis Zikas
General Adversary Structures in Byzantine Agreement and Multi-Party Computation with Active and Omission Corruption
Theory of Cryptography Conference — TCC 2024 (to appear).
A preliminary full version is available here: [ PDF ]

Xiangyu Liu, Ioannis Tzannetos, and Vassilis Zikas
Adaptor Signatures: New Security Definition and A Generic Construction for NP Relations
Advances in Cryptology — ASIACRYPT 2024 (to appear).
A preliminary full version is available here: [ PDF ]

Timothé Albouy, Davide Frey, Ran Gelles, Carmit Hazay, Michel Raynal, Elad Michael Schiller, François Taïani, and Vassilis Zikas
Near-Optimal Communication Byzantine Reliable Broadcast under a Message Adversary
Conference on Principles of Distributed Systems — OPODIS 2024 (to appear).
A preliminary full version is available here: [ PDF ]

Yun Lu, Malik Magdon-Ismail, Yu Wei, and Vassilis Zikas
Eureka: A General Framework for Black-box Differential Privacy Estimators
IEEE Symposium on Security and Privacy — S&P 2024, IEEE, pp 913–931, 2024.
A preliminary full version is available here: [ PDF ]

Christian Badertscher, Peter Gazi, Aggelos Kiayias, Alexander Russell, and Vassilis Zikas:
Consensus Redux: Distributed Ledgers in the Face of Adversarial Supremacy
IEEE Computer Security Foundations Symposium —CSF 2024, IEEE, pp 143–158, 2024.
A preliminary full version is available here: [ PDF ]

Ran Cohen, Pouyan Forghani, Juan Garay, Rutvik Patel, and Vassilis Zikas
Concurrent Asynchronous Byzantine Agreement in Expected-Constant Rounds, Revisited
Theory of Cryptography Conference — TCC 2023, LNCS, Springer, vol 14372, pp 422–451, 2023.
A preliminary full version is available here: [ PDF ]

Lindsey Kennard, Muhammad Ishaq, Benjamin Levy, Ana Milanova, Ben Sherman, and Vassilis Zikas.
COMBINE: COMpilation and Backend-INdependent vEctorization for Multi-Party Computation
ACM Conference on Computer and Communications Security — CCS 2023, ACM, pp 2531–2545, 2023.
A preliminary full version is available here: [ PDF ]

Ran Cohen, Juan Garay, and Vassilis Zikas.
Completeness Theorems for Adaptively Secure Broadcast
Advances in Cryptology — CRYPTO 2023, LNCS, Springer, vol 14081, pp 3–38, 2023
A preliminary full version is available here: [ PDF ]

Michele Ciampi, Rafail Ostrovsky, Hendrik Waldner, and Vassilis Zikas
Round-Optimal and Communication-Efficient Multiparty Computation
Advances in Cryptology — EUROCRYPT 2022, LNCS, Springer, vol 13275, pp 65–95, 2022.
A preliminary full version is available here: [ PDF ]

Michele Ciampi, Yun Lu, and Vassilis Zikas
Collusion-Preserving Computation without a Mediator
IEEE Computer Security Foundations Symposium —CSF 2022, IEEE, pp 211–226, 2022.
A preliminary full version is available here: [ PDF ]

John Andrews, Michele Ciampi, and Vassilis Zikas
Etherless Ethereum Tokens: Simulating Native Tokens in Ethereum
Symposium on Cyber Security, Cryptology and Machine Learning —CSCML 2022, LNCS, Springer, vol 13301, pp 388–407, 2022.
(Best Paper Award)
A preliminary full version is available here: [ PDF ]

Michele Ciampi, Muhammad Ishaq, Malik Magdon-Ismail, Rafail Ostrovsky and Vassilis Zikas
FairMM: A Fast and Frontrunning-Resistant Crypto Market-Maker
Symposium on Cyber Security, Cryptology and Machine Learning —CSCML 2022, LNCS, Springer, vol 13301, pp 428–466, 2022.
A preliminary full version is available here: [ PDF ]

Nishanth Chandran, Pouyan Forghani, Juan A. Garay, Rafail Ostrovsky, Rutvik Patel, and Vassilis Zikas
Universally Composable Almost-Everywhere Secure Computation.
Conference on Information-Theoretic Cryptography —ITC 2022, LIPIcs, vol 230, pp 14:1–14:25, 2022.
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, LNCS, Springer, vol 12827, pp 3–32, 2021.
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, LNCS, Springer, vol 12698, pp 399–428, 2021.
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, LNCS, Springer, vol 13043, pp 626–657, 2021.
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 

Nishanth Chandran, Juan Garay, Rafail Ostrovsky, and Vassilis Zikas
On Adaptive Security, Erasures and Network Assumptions in MPC with Polylogarithmic Communication Locality
Manuscript.

Yun Lu, Malik Magdon-Ismail, Yu Wei, and Vassilis Zikas
Privacy-Utility Tradeoff of OLS with Random Projections
Manuscript.

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

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.