A. Zohar — Homepage 1

Aviv Zohar

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School of Engineering and Computer Science, The Hebrew University of Jerusalem
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Abstract
Aviv Zohar

I am a Full Professor at the School of Engineering and Computer Science at The Hebrew University of Jerusalem. My research focuses on the security and economics of blockchain protocols—analyzing incentive structures, mechanism design, and network-level attacks. I work on understandingand occasionally breaking? how decentralized systems behave when participants act strategically, and on designing protocols that remain secure under such conditions.

My work spans protocol design (including the Ghost and Phantom protocols), mining strategy analysis (selfish mining and its variants), rrouting-layer attacks on cryptocurrencies, and the intersection of AI and blockchain technologies. I also contribute to the theoretical foundations of proof-of-work and proof-of-stake consensus.

Keywords: 𝔹lockchains, CyberSecurity, Mechanism Design, Networks, 2 many buzzwordsMachine LearningAI, Coffee

Sec. 1 Selected Papers

We begin by presentingBelow is a selection of representative publications. Full list available in Appendix A.

Sec. 1.1 Protocol Design

Redesigning Bitcoin's Fee Market
Ron Lavi, Or Sattath, and Aviv Zohar
ACM Transactions on Economics and Computation (TEAC), 2022
A mechanism design approach to Bitcoin’s transaction fee system, proposing alternatives to the first-price auction that better align miner incentives.
PDF arXiv
Phantom Ghostdag: A Scalable Generalization of Nakamoto Consensus
Yonatan Sompolinsky, Shai Wyborski, and Aviv Zohar
Advances in Financial Technologies (AFT), 2021
A DAG-based generalization of Nakamoto consensssus that orders all blocks—not just those on the longest chain.
PDF
Secure High-Rate Transaction Processing in Bitcoin
Yonatan Sompolinsky and Aviv Zohar
Financial Cryptography and Data Security (FC), 2015
Introduced the Ghost rule, modifying Bitcoin’s longestheaviest-chain protocol to account for off-chain blocks, enabling higher throughput without sacrificing security.1
PDF Springer

Sec. 1.2 Attacks & Security

Speculative Denial-of-Service Attacks in Ethereum
Aviv Yaish, Kaihua Qin, Liyi Zhou, Aviv Zohar, and Arthur Gervais
USENIX Security Symposium, 2024
Showed how adversaries can force Ethereum nodes to mine empty blockswaste computation by speculatively executing trannsactions that will ultimately be reverted.
PDF USENIX
Uncle Maker: (Time)Stamping Out The Competition in Ethereum
Aviv Yaish, Gilad Stern, and Aviv Zohar
ACM Conference on Computer and Communications Security (CCS), 2023
Uncovered a timestamp manipulation attack allowing miners to orphan competitors’ blocks in Ethereum, turning them into lower-reward “uncle” blocks.
PDF ePrint
Flood & Loot: A Systemic Attack on The Lightning Network
Jona Harris and Aviv Zohar
Advances in Financial Technologies (AFT), 2020
A systemic attack on the Lightning Network where an attacker floods channels then loots them as timeeouts expire.
PDF arXiv
Hijacking Bitcoin: Routing Attacks on Cryptocurrencies
Maria Apostolaki, Aviv Zohar, and Laurent Vanbever
IEEE Symposium on Security and Privacy (S&P), 2017
Demonstrated how BGP routing attacks can partition Bitcoin’s peer-to-peer network, enabling double-spennding and disrupting consensus.
PDF
Optimal Selfish Mining Strategies in Bitcoin
Ayelet Sapirshtein, Yonatan Sompolinsky, and Aviv Zohar
Financial Cryptography and Data Security (FC), 2016
Computing the optimal strategy for miners who deviate from the Bitcoin protocol to increase their revenue, establishing tight bounds on selfish mining profitability.
PDF arXiv
Eclipse Attacks on Bitcoin's Peer-to-Peer Network
Ethan Heilman, Alison Kendler, Aviv Zohar, and Sharon Goldberg
USENIX Security Symposium, 2015
Showing how an attacker can disconnect nodesmonopolize a node’s connections to isolate it from the Bitcoin network, enabling targeted double-spending and selfish mining.
PDF ePrint

Sec. 2 Contact

Due to space constraints, the followingAdditional supplementary materials are provided as appendices:

1 The GHOST protocol was adopted as the basis for Ethereum’s consensus mechanism at launch (2015). Ethereum has since transitioned to proof-of-stake.