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Documents authored by Schlegel, Christoph

Document
Extended Abstract
DOI: 10.4230/LIPIcs.AFT.2026.16
On Sybil-Proof Mechanisms (Extended Abstract)

Authors: Minghao Pan, Bruno Mazorra, Christoph Schlegel, and Akaki Mamageishvili

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

Abstract
We show that in the single-parameter mechanism design environment, the only non-wasteful, symmetric, incentive compatible and Sybil-proof direct mechanism is a second price auction with symmetric tie-breaking. Thus, if there is private information, lotteries or other mechanisms that do not always allocate to a highest-value bidder are not Sybil-proof or not incentive compatible. Moreover, we show that our main (im)possibility result extends beyond linear valuations, but not to multi-unit object allocation with unit-demand bidders. We also provide examples of mechanisms (with higher interim payoff for the bidders than a second price auction) that satisfy all of the other axioms and a weaker, Bayesian notion of Sybil-proofness. Thus, our (im)possibility result does not generalise to the Bayesian setting and we have a larger design space: With Sybil constraints, equivalence between dominant strategy and Bayesian implementation (that holds in classical single-parameter mechanism design without Sybils) no longer holds.
Cite as

Minghao Pan, Bruno Mazorra, Christoph Schlegel, and Akaki Mamageishvili. On Sybil-Proof Mechanisms (Extended Abstract). In 8th Conference on Advances in Financial Technologies (AFT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 395, pp. 16:1-16:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{pan_et_al:LIPIcs.AFT.2026.16,
  author =	{Pan, Minghao and Mazorra, Bruno and Schlegel, Christoph and Mamageishvili, Akaki},
  title =	{{On Sybil-Proof Mechanisms}},
  booktitle =	{8th Conference on Advances in Financial Technologies (AFT 2026)},
  pages =	{16:1--16:3},
  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.2026.16},
  URN =		{urn:nbn:de:0030-drops-278700},
  doi =		{10.4230/LIPIcs.AFT.2026.16},
  annote =	{Keywords: Sybils, Mechanism Design, Blockchain}
}
Document
DOI: 10.4230/LIPIcs.AFT.2026.19
Competing Auctions in Intermediated Markets

Authors: Bruno Mazorra, Minghao Pan, and Christoph Schlegel

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

Abstract
We analyze competing auctions in intermediated markets, where a seller selects among parallel mechanisms for the sale of a single good, most prominently the relay-and-protocol architecture of proposer-builder separation in Ethereum. When the intermediary can enforce single-homing on its bidders, sealed-bid second-price intermediary auctions fully unravel into the sealed first-price principal auction; open bidding-format intermediaries unravel only partially, collapsing into first-price in equilibrium under symmetric latency and sorting fast bidders to the intermediary under asymmetric latency. Any last-look advantage is removed through the availability of a credible sealed bidding channel. These results extend to multi-plexing environments (no enforcement by the intermediary). While the unraveling result indicates that the availability of a sealed first-price bidding channel pushes the overall market to the same auction structure, the very assumption of the credibility of such a channel is problematic, as the seller may have an incentive to leak information: a first-price auction is leakage-resistant in the presence of a single "fast" bidder but not against two or more. However, if the seller can credibly commit to not leak bids, it is optimal for them to do so. A main motivation is the forthcoming Glamsterdam update of Ethereum: our analysis suggests that the availability of an in-protocol (first-price) bidding channel severely limits the design space for out-of-protocol auctions by relays and other intermediaries.
Cite as

Bruno Mazorra, Minghao Pan, and Christoph Schlegel. Competing Auctions in Intermediated Markets. In 8th Conference on Advances in Financial Technologies (AFT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 395, pp. 19:1-19:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{mazorra_et_al:LIPIcs.AFT.2026.19,
  author =	{Mazorra, Bruno and Pan, Minghao and Schlegel, Christoph},
  title =	{{Competing Auctions in Intermediated Markets}},
  booktitle =	{8th Conference on Advances in Financial Technologies (AFT 2026)},
  pages =	{19:1--19:21},
  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.2026.19},
  URN =		{urn:nbn:de:0030-drops-278738},
  doi =		{10.4230/LIPIcs.AFT.2026.19},
  annote =	{Keywords: Competing auctions, proposer-builder separation, maximal extractable value}
}
Document
DOI: 10.4230/LIPIcs.AFT.2026.20
Just-In-Time Resale in an Ahead-Of-Time Auction for Faster Execution

Authors: Burak Öz, Akaki Mamageishvili, Christoph Schlegel, and Ali Taslimi

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

Abstract
We study Arbitrum’s Timeboost auction, an ahead-of-time mechanism that sells a 200 ms ordering advantage in an otherwise first-come, first-served transaction ordering policy. The market naturally divides into two phases: a competition phase, in which the dominant searchers compete directly in the primary auction, and a coordination phase, in which they source fast-lane access through Kairos, a Just-in-Time resale intermediary. We use auction bids, time-boosted transactions, and on-chain payment traces to study how well ahead-of-time bids predict realized CEX-DEX arbitrage profits and how the emergence of resale changes surplus allocation. We find that ahead-of-time bids are noisy predictors of short-horizon arbitrage profits. During the competition phase, bid-profit correlations are statistically significant but economically modest at the round level, while correlations increase when profits are aggregated over longer horizons. This suggests that bidders can identify favorable market conditions but face substantial uncertainty about the realized value of any individual one-minute fast-lane interval. After the Kairos transition, competition in the primary auction weakens sharply: in our focused transition-analysis window, paid bids fall from 62.7% of the top bid before the transition to 14.8% thereafter, while total searcher profits remain broadly similar. The resulting dynamics are most consistent with coordination through a common intermediary rather than direct competition in the primary auction. More broadly, our findings suggest that ahead-of-time allocation mechanisms can be vulnerable to secondary-market intermediation when competition among dominant participants is weak.
Cite as

Burak Öz, Akaki Mamageishvili, Christoph Schlegel, and Ali Taslimi. Just-In-Time Resale in an Ahead-Of-Time Auction for Faster Execution. In 8th Conference on Advances in Financial Technologies (AFT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 395, pp. 20:1-20:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{oz_et_al:LIPIcs.AFT.2026.20,
  author =	{\"{O}z, Burak and Mamageishvili, Akaki and Schlegel, Christoph and Taslimi, Ali},
  title =	{{Just-In-Time Resale in an Ahead-Of-Time Auction for Faster Execution}},
  booktitle =	{8th Conference on Advances in Financial Technologies (AFT 2026)},
  pages =	{20:1--20:23},
  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.2026.20},
  URN =		{urn:nbn:de:0030-drops-278740},
  doi =		{10.4230/LIPIcs.AFT.2026.20},
  annote =	{Keywords: ahead-of-time auctions, secondary markets, Timeboost, arbitrage}
}
Document
DOI: 10.4230/LIPIcs.AFT.2024.21
Searcher Competition in Block Building

Authors: Akaki Mamageishvili, Christoph Schlegel, and Benny Sudakov

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

Abstract
We study the amount of maximal extractable value (MEV) captured by validators, as a function of searcher (or order flow provider) competition in blockchains with competitive block building markets such as Ethereum. We argue that the core is a suitable solution concept in this context that makes robust predictions that are independent of implementation details or specific mechanisms chosen. We characterize how much value validators extract in the core and quantify the surplus share of validators as a function of searcher competition. Searchers can obtain at most the marginal value increase of the winning block relative to the best block that can be built without their bundles. Dually this gives a lower bound on the value extracted by the validator. If arbitrages are easy to find and many searchers find similar bundles, the validator gets paid all value almost surely, while searchers can capture most value if there is little searcher competition per arbitrage. For the case of passive block-proposers we study, moreover, mechanisms that implement core allocations in dominant strategies and find that for submodular value, there is a unique dominant-strategy incentive compatible core-selecting mechanism that gives each searcher exactly their marginal value contribution to the winning block.
Cite as

Akaki Mamageishvili, Christoph Schlegel, and Benny Sudakov. Searcher Competition in Block Building. In 6th Conference on Advances in Financial Technologies (AFT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 316, pp. 21:1-21:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{mamageishvili_et_al:LIPIcs.AFT.2024.21,
  author =	{Mamageishvili, Akaki and Schlegel, Christoph and Sudakov, Benny},
  title =	{{Searcher Competition in Block Building}},
  booktitle =	{6th Conference on Advances in Financial Technologies (AFT 2024)},
  pages =	{21:1--21:12},
  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.2024.21},
  URN =		{urn:nbn:de:0030-drops-209579},
  doi =		{10.4230/LIPIcs.AFT.2024.21},
  annote =	{Keywords: MEV, Block Building, Searchers, Proposer Builder Separation, Core}
}

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