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Documents authored by Avarikioti, Zeta

Document
DOI: 10.4230/LIPIcs.AFT.2026.1
BitVM: Quasi-Turing Complete Computation on Bitcoin

Authors: Lukas Aumayr, Zeta Avarikioti, Robin Linus Woll, Matteo Maffei, Andrea Pelosi, Christos Stefo, and Alexei Zamyatin

Published in: LIPIcs, Volume 395, 8th Conference on Advances in Financial Technologies (AFT 2026)

Abstract
A long-standing question in the blockchain community is which class of computations is efficiently expressible in cryptocurrencies with limited scripting languages, such as Bitcoin Script. Such languages expose a reduced trusted computing base, thereby being less prone to hacks and vulnerabilities, but have long been believed to support only limited classes of payments. In this work, we confute this long-standing belief by showing for the first time that arbitrary computations can be encoded in today’s Bitcoin Script without introducing any language modification or additional security assumptions, such as trusted hardware, trusted parties, or committees with an honest majority. We present BitVM, a two-party protocol that realizes a generic virtual machine by combining cryptographic primitives and economic incentives. We conduct a formal analysis of BitVM, characterizing its functionality, system assumptions, and security properties. We further demonstrate the practicality of our approach by implementing a prototype and performing an experimental evaluation: in the optimistic case (i.e., when parties agree), our protocol requires just three on-chain transactions, whereas in the pessimistic case, the number of transactions grows logarithmically with the size of the virtual machine. We exemplify the deployment potential of BitVM by building a Bitcoin-sidechain bridge application. This work not only solves a long-standing theoretical problem, but it also promises a strong practical impact, enabling the development of complex applications in Bitcoin.
Cite as

Lukas Aumayr, Zeta Avarikioti, Robin Linus Woll, Matteo Maffei, Andrea Pelosi, Christos Stefo, and Alexei Zamyatin. BitVM: Quasi-Turing Complete Computation on Bitcoin. In 8th Conference on Advances in Financial Technologies (AFT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 395, pp. 1:1-1:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{aumayr_et_al:LIPIcs.AFT.2026.1,
  author =	{Aumayr, Lukas and Avarikioti, Zeta and Woll, Robin Linus and Maffei, Matteo and Pelosi, Andrea and Stefo, Christos and Zamyatin, Alexei},
  title =	{{BitVM: Quasi-Turing Complete Computation on Bitcoin}},
  booktitle =	{8th Conference on Advances in Financial Technologies (AFT 2026)},
  pages =	{1:1--1:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-451-2},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{395},
  editor =	{Kiayias, Aggelos and Kyropoulou, Maria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2026.1},
  URN =		{urn:nbn:de:0030-drops-278556},
  doi =		{10.4230/LIPIcs.AFT.2026.1},
  annote =	{Keywords: Bitcoin, quasi-Turing completeness, off-chain protocols, bridge}
}
Document
DOI: 10.4230/LIPIcs.AFT.2026.30
Optimal Reward Allocation via Proportional Splitting

Authors: Lukas Aumayr, Zeta Avarikioti, Dimitris Karakostas, Karl Kreder, and Shreekara Shastry

Published in: LIPIcs, Volume 395, 8th Conference on Advances in Financial Technologies (AFT 2026)

Abstract
Following the publication of Bitcoin’s arguably most famous attack, selfish mining, various works have introduced mechanisms to enhance blockchain systems' game-theoretic resilience. The only proof-of-work reward rule with a Nash-equilibrium guarantee, FruitChains, demands reward finality on the order of days. The rules that settle in minutes have no such guarantee, and one of them, Reward Splitting, still outperforms FruitChains on most of the metrics that matter in deployment. This paper closes that gap between theory and practice. We introduce FairChain, a two-level transformation for any proof-of-work Nakamoto-style protocol. At the protocol layer, FairChain records low-difficulty samples called workshares alongside blocks. At the reward layer, it applies Proportional Reward Splitting (PRS): each height’s reward is divided among the competing work objects in proportion to the intrinsic work behind them, with workshares supplying a fresh power estimate at every height. The fork-choice rule and block-production loop are left untouched, so the host chain’s security carries over unchanged. Workshares can be discarded once the corresponding rewards mature, leaving zero on-chain footprint. We prove FairChain is a ρ-coalition-safe ε-Nash equilibrium for sufficiently large parameters, matching FruitChains in theory. To evaluate practical performance, we leverage Markov decision processes and compute the optimal adversarial policy under each utility function, rather than the gain of any one attack. At a six-block confirmation window, FairChain raises the deviation threshold to 38% of mining power and beats every mechanism in that framework on incentive compatibility, subversion gain (except FruitChains above 42%), and censorship susceptibility (except FruitChains below 25%). Our construction has been adopted by a live PoW blockchain, with sub-kilobyte per-block storage overhead in deployment.
Cite as

Lukas Aumayr, Zeta Avarikioti, Dimitris Karakostas, Karl Kreder, and Shreekara Shastry. Optimal Reward Allocation via Proportional Splitting. In 8th Conference on Advances in Financial Technologies (AFT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 395, pp. 30:1-30:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{aumayr_et_al:LIPIcs.AFT.2026.30,
  author =	{Aumayr, Lukas and Avarikioti, Zeta and Karakostas, Dimitris and Kreder, Karl and Shastry, Shreekara},
  title =	{{Optimal Reward Allocation via Proportional Splitting}},
  booktitle =	{8th Conference on Advances in Financial Technologies (AFT 2026)},
  pages =	{30:1--30:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-451-2},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{395},
  editor =	{Kiayias, Aggelos and Kyropoulou, Maria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2026.30},
  URN =		{urn:nbn:de:0030-drops-278848},
  doi =		{10.4230/LIPIcs.AFT.2026.30},
  annote =	{Keywords: blockchain, proof-of-work, fairness, game-theory, rewards}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.AFT.2025
LIPIcs, Volume 354, AFT 2025, Complete Volume

Authors: Zeta Avarikioti and Nicolas Christin

Published in: LIPIcs, Volume 354, 7th Conference on Advances in Financial Technologies (AFT 2025)

Abstract
LIPIcs, Volume 354, AFT 2025, Complete Volume
Cite as

7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 1-802, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@Proceedings{avarikioti_et_al:LIPIcs.AFT.2025,
  title =	{{LIPIcs, Volume 354, AFT 2025, Complete Volume}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{1--802},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-400-0},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{354},
  editor =	{Avarikioti, Zeta and Christin, Nicolas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2025},
  URN =		{urn:nbn:de:0030-drops-248097},
  doi =		{10.4230/LIPIcs.AFT.2025},
  annote =	{Keywords: LIPIcs, Volume 354, AFT 2025, Complete Volume}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.AFT.2025.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Zeta Avarikioti and Nicolas Christin

Published in: LIPIcs, Volume 354, 7th Conference on Advances in Financial Technologies (AFT 2025)

Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as

7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 0:i-0:xx, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{avarikioti_et_al:LIPIcs.AFT.2025.0,
  author =	{Avarikioti, Zeta and Christin, Nicolas},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{0:i--0:xx},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-400-0},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{354},
  editor =	{Avarikioti, Zeta and Christin, Nicolas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2025.0},
  URN =		{urn:nbn:de:0030-drops-248080},
  doi =		{10.4230/LIPIcs.AFT.2025.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
DOI: 10.4230/LIPIcs.AFT.2024.11
Bribe & Fork: Cheap PCN Bribing Attacks via Forking Threat

Authors: Zeta Avarikioti, Paweł Kędzior, Tomasz Lizurej, and Tomasz Michalak

Published in: LIPIcs, Volume 316, 6th Conference on Advances in Financial Technologies (AFT 2024)

Abstract
In this work, we reexamine the vulnerability of Payment Channel Networks (PCNs) to bribing attacks, where an adversary incentivizes blockchain miners to deliberately ignore a specific transaction to undermine the punishment mechanism of PCNs. While previous studies have posited a prohibitive cost for such attacks, we show that this cost can be dramatically reduced (to approximately $125), thereby increasing the likelihood of these attacks. To this end, we introduce Bribe & Fork, a modified bribing attack that leverages the threat of a so-called feather fork which we analyze with a novel formal model for the mining game with forking. We empirically analyze historical data of some real-world blockchain implementations to evaluate the scale of this cost reduction. Our findings shed more light on the potential vulnerability of PCNs and highlight the need for robust solutions.
Cite as

Zeta Avarikioti, Paweł Kędzior, Tomasz Lizurej, and Tomasz Michalak. Bribe & Fork: Cheap PCN Bribing Attacks via Forking Threat. In 6th Conference on Advances in Financial Technologies (AFT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 316, pp. 11:1-11:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{avarikioti_et_al:LIPIcs.AFT.2024.11,
  author =	{Avarikioti, Zeta and K\k{e}dzior, Pawe{\l} and Lizurej, Tomasz and Michalak, Tomasz},
  title =	{{Bribe \& Fork: Cheap PCN Bribing Attacks via Forking Threat}},
  booktitle =	{6th Conference on Advances in Financial Technologies (AFT 2024)},
  pages =	{11:1--11:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-345-4},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{316},
  editor =	{B\"{o}hme, Rainer and Kiffer, Lucianna},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2024.11},
  URN =		{urn:nbn:de:0030-drops-209473},
  doi =		{10.4230/LIPIcs.AFT.2024.11},
  annote =	{Keywords: Blockchain, Payment Channels Networks, Timelock Bribing, Feather Forking}
}
Document
DOI: 10.4230/LIPIcs.AFT.2024.13
Musketeer: Incentive-Compatible Rebalancing for Payment Channel Networks

Authors: Zeta Avarikioti, Stefan Schmid, and Samarth Tiwari

Published in: LIPIcs, Volume 316, 6th Conference on Advances in Financial Technologies (AFT 2024)

Abstract
In this work, we revisit the severely limited throughput problem of cryptocurrencies and propose a novel rebalancing approach for Payment Channel Networks (PCNs). PCNs are a popular solution for increasing the blockchain throughput, however, their benefit depends on the overall users' liquidity. Rebalancing mechanisms are the state-of-the-art approach to maintaining high liquidity in PCNs. However, existing opt-in rebalancing mechanisms exclude users that may assist in rebalancing for small service fees, leading to suboptimal solutions and under-utilization of the PCNs' bounded liquidity. We introduce the first rebalancing approach for PCNs that includes all users, following a "all for one and one for all" design philosophy that yields optimal throughput. The proposed approach introduces a double-auction rebalancing problem, which we term Musketeer, where users can participate as buyers (paying fees to rebalance) or sellers (charging fees to route transactions). The desired properties tailored to the unique characteristics of PCNs are formally defined, including the novel game-theoretic property of cyclic budget balance that is a stronger variation of strong budget balance. Basic results derived from auction theory, including an impossibility and multiple mechanisms that either achieve all desiderata under a relaxed model or sacrifice one of the properties, are presented. We also propose a novel mechanism that leverages time delays as an additional cost to users. This mechanism is provably truthful, cyclic budget balanced, individually rational and economic efficient but only with respect to liquidity.
Cite as

Zeta Avarikioti, Stefan Schmid, and Samarth Tiwari. Musketeer: Incentive-Compatible Rebalancing for Payment Channel Networks. In 6th Conference on Advances in Financial Technologies (AFT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 316, pp. 13:1-13:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{avarikioti_et_al:LIPIcs.AFT.2024.13,
  author =	{Avarikioti, Zeta and Schmid, Stefan and Tiwari, Samarth},
  title =	{{Musketeer: Incentive-Compatible Rebalancing for Payment Channel Networks}},
  booktitle =	{6th Conference on Advances in Financial Technologies (AFT 2024)},
  pages =	{13:1--13:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-345-4},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{316},
  editor =	{B\"{o}hme, Rainer and Kiffer, Lucianna},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2024.13},
  URN =		{urn:nbn:de:0030-drops-209494},
  doi =		{10.4230/LIPIcs.AFT.2024.13},
  annote =	{Keywords: Blockchains, Payment Channel Networks, Rebalancing, Game Theory}
}

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