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Documents authored by Karakostas, Dimitris

Artifact
Software
DOI: 10.4230/artifacts.27543
StakeNote

Authors: Bernardo David and Dimitris Karakostas

Abstract
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Bernardo David, Dimitris Karakostas. StakeNote (Software, Source Code). Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@misc{dagstuhl-artifact-27543,
   title = {{StakeNote}}, 
   author = {David, Bernardo and Karakostas, Dimitris},
   note = {Software, swhId: \href{https://archive.softwareheritage.org/swh:1:dir:2ee7704e94b9fa3526b672fabc2b7cc381af6830;origin=https://github.com/commonprefix/stakenote;visit=swh:1:snp:ca71b6e0e2c822a67d4b82fd21131abf4f65b2d0;anchor=swh:1:rev:456c0b56ca9c43218f88e554ac56bbd9d0a7c243}{\texttt{swh:1:dir:2ee7704e94b9fa3526b672fabc2b7cc381af6830}} (visited on 2026-10-02)},
   url = {https://github.com/commonprefix/stakenote},
   doi = {10.4230/artifacts.27543},
}
Artifact
Software
DOI: 10.4230/artifacts.27946
commonprefix/proportional-reward-splitting-MDP

Authors: Dimitris Karakostas

Abstract
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Dimitris Karakostas. commonprefix/proportional-reward-splitting-MDP (Software, Source Code). Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@misc{evalrepo,
   title = {{commonprefix/proportional-reward-splitting-MDP}}, 
   author = {Karakostas, Dimitris},
   note = {Software, swhId: \href{https://archive.softwareheritage.org/swh:1:dir:4a244dd0f68a10c4abb1fa0bf218527ba36dd085;origin=https://github.com/commonprefix/proportional-reward-splitting-MDP;visit=swh:1:snp:a0413a5ae0edfe07508e8ac0499765717efbc483;anchor=swh:1:rev:a2b845a119942b5960e523f3200d5c32003d3f39}{\texttt{swh:1:dir:4a244dd0f68a10c4abb1fa0bf218527ba36dd085}} (visited on 2026-10-02)},
   url = {https://github.com/commonprefix/proportional-reward-splitting-MDP},
   doi = {10.4230/artifacts.27946},
}
Document
DOI: 10.4230/LIPIcs.AFT.2026.8
StakeNote: A Proof-Of-Stake Protocol for CryptoNote Payments

Authors: Bernardo David and Dimitris Karakostas

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

Abstract
This work proposes StakeNote, a distributed ledger protocol that combines Proof-of-Stake (PoS) with privacy and anonymity preserving payments. The protocol combines Ouroboros Praos, a provably secure PoS protocol, with CryptoNote, a privacy-preserving payment system based on ring signatures which has been widely used in practice. We prove that StakeNote inherits the security guarantees of Ouroboros Praos and the privacy guarantees of CryptoNote. We also demonstrate its practicality via a proof of concept implementation of its cryptographic components, showing that block signing requires less than 25 ms and eligibility proofs are approx. 3 KB for anonymity sets of size 16. Finally, we discuss heuristic enhancements that potentially increase privacy and enable dynamic participation.
Cite as

Bernardo David and Dimitris Karakostas. StakeNote: A Proof-Of-Stake Protocol for CryptoNote Payments. In 8th Conference on Advances in Financial Technologies (AFT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 395, pp. 8:1-8:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{david_et_al:LIPIcs.AFT.2026.8,
  author =	{David, Bernardo and Karakostas, Dimitris},
  title =	{{StakeNote: A Proof-Of-Stake Protocol for CryptoNote Payments}},
  booktitle =	{8th Conference on Advances in Financial Technologies (AFT 2026)},
  pages =	{8:1--8:24},
  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.2026.8},
  URN =		{urn:nbn:de:0030-drops-278622},
  doi =		{10.4230/LIPIcs.AFT.2026.8},
  annote =	{Keywords: Proof-of-Stake, anonymity, CryptoNote, ring signatures}
}
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.
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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
DOI: 10.4230/OASIcs.Tokenomics.2019.7
Cryptocurrency Egalitarianism: A Quantitative Approach

Authors: Dimitris Karakostas, Aggelos Kiayias, Christos Nasikas, and Dionysis Zindros

Published in: OASIcs, Volume 71, International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2019)

Abstract
Since the invention of Bitcoin one decade ago, numerous cryptocurrencies have sprung into existence. Among these, proof-of-work is the most common mechanism for achieving consensus, whilst a number of coins have adopted "ASIC-resistance" as a desirable property, claiming to be more "egalitarian," where egalitarianism refers to the power of each coin to participate in the creation of new coins. While proof-of-work consensus dominates the space, several new cryptocurrencies employ alternative consensus, such as proof-of-stake in which block minting opportunities are based on monetary ownership. A core criticism of proof-of-stake revolves around it being less egalitarian by making the rich richer, as opposed to proof-of-work in which everyone can contribute equally according to their computational power. In this paper, we give the first quantitative definition of a cryptocurrency’s egalitarianism. Based on our definition, we measure the egalitarianism of popular cryptocurrencies that (may or may not) employ ASIC-resistance, among them Bitcoin, Ethereum, Litecoin, and Monero. Our simulations show, as expected, that ASIC-resistance increases a cryptocurrency’s egalitarianism. We also measure the egalitarianism of a stake-based protocol, Ouroboros, and a hybrid proof-of-stake/proof-of-work cryptocurrency, Decred. We show that stake-based cryptocurrencies, under correctly selected parameters, can be perfectly egalitarian, perhaps contradicting folklore belief.
Cite as

Dimitris Karakostas, Aggelos Kiayias, Christos Nasikas, and Dionysis Zindros. Cryptocurrency Egalitarianism: A Quantitative Approach. In International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2019). Open Access Series in Informatics (OASIcs), Volume 71, pp. 7:1-7:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{karakostas_et_al:OASIcs.Tokenomics.2019.7,
  author =	{Karakostas, Dimitris and Kiayias, Aggelos and Nasikas, Christos and Zindros, Dionysis},
  title =	{{Cryptocurrency Egalitarianism: A Quantitative Approach}},
  booktitle =	{International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2019)},
  pages =	{7:1--7:21},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-108-5},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{71},
  editor =	{Danos, Vincent and Herlihy, Maurice and Potop-Butucaru, Maria and Prat, Julien and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.Tokenomics.2019.7},
  URN =		{urn:nbn:de:0030-drops-119715},
  doi =		{10.4230/OASIcs.Tokenomics.2019.7},
  annote =	{Keywords: blockchain, egalitarianism, cryptocurrency, economics, proof-of-work, proof-of-stake}
}

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