From e04a9e2b02264601ace683b640dafdbaeb9eb40f Mon Sep 17 00:00:00 2001 From: "O. Saguillo" <47833532+saguillo2000@users.noreply.github.com> Date: Thu, 18 Dec 2025 16:55:54 +0100 Subject: [PATCH 1/4] Create FRP_proposal --- FRPs/FRP_proposal | 129 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 129 insertions(+) create mode 100644 FRPs/FRP_proposal diff --git a/FRPs/FRP_proposal b/FRPs/FRP_proposal new file mode 100644 index 0000000..6425e06 --- /dev/null +++ b/FRPs/FRP_proposal @@ -0,0 +1,129 @@ +--- +id: +title: SoK: Proposer-Builder Separation and Beyond +team: Oriol SAGUILLO, Prerna Prabhakar AROTE, Lucianna KIFFER (IMDEA Networks Institute) +created: +--- + +## Background and Problem Statement + +Proposer–Builder Separation (PBS) [7][11][5], together with MEV-Boost, represents the first widely adopted approach for decoupling block construction from +block proposal in Ethereum. These mechanisms have enabled a more efficient and competitive market for block building and MEV extraction [2][28][1]. However, +their current realization relies predominantly on off-chain relayers, introducing non-trivial trust assumptions and creating centralization pressures +within the block production pipeline [27][11][10]. In response to these limitations, a broad spectrum of alternative designs +and protocol-level enhancements has been proposed. These include (but are not limited to) enshrined PBS [20][14], encrypted and privacy-preserving block +building [13][23][12], MEV burn mechanisms [8], execution tickets [4], execution auctions [3], inclusion lists [FOCIL, AUCIL, COMIS, etc.] [26][24][25], and +cross-domain PBS architectures [19][18][16]. Each class of design targets distinct challenges of the existing PBS model, such as reducing relayer dependence, +mitigating censorship and liveness risks, improving incentive alignment across participants, and strengthening security guarantees for validators and order-flow +providers. +However, discussions of these designs, including their security assumptions and trade-offs are fragmented across blog posts, research articles, and forum +discussions. As a result, there is no single, comprehensive resource that systematically compares these approaches or clearly outlines their shared objectives, +design trade-offs, and remaining open challenges. The goal of this project is to compile and systematize existing PBS-related +designs across different layers of the blockchain protocol. The project will identify and categorize the desired properties of proposer–builder separation mech- +anisms, analyze known and potential attack vectors— Sandwich attack, Frontrunning attack [7][9], Back-running attack[21], Free-option problem[15], Timing +game[22], Equivocation attacks [17], Bribery attack[6], etc. , and highlight open research questions. By providing a unified framework for understanding current +proposals and their limitations across both industry and academia, this work aims to serve as a reference for researchers, protocol designers, and the broader +blockchain community. + +## Plan and Deliverables + +The study will proceed in the following steps: +• Compile and review existing literature on Proposer–Builder Separation (PBS), including current implementations and proposed alternative de- +signs related to any step in the workflow from transaction submission to block validation. +• Formalize the key properties required for a secure, efficient, and decentralized block-building system. +• Analyze known and potential attack vectors that obstruct the realization of these properties, and discuss their implications for different PBS de- +signs. +• Synthesize the above analysis into a unified taxonomy of PBS design trade-offs, highlighting open problems and directions for future research + +## References + +[1] Hayden Adams, Brad Bachu, Alex Nezlobin, Sara Reynolds, Dan Robinson, +Mark Toda, Xin Wan, Zach Wong, and Ciamac Moallemi. The protocol fee discount auction. 2025. +[2] Orestis Alpos, Lioba Heimbach, Kartik Nayak, and Sarisht Wadhwa. +Censorship-resistant sealed-bid auctions on blockchains. Cryptology ePrint Archive, 2025. +[3] Jonah B. Execution auctions as an alternative to execution +tickets. https://ethresear.ch/t/execution-auctions-as-an-alternative-to- +execution-tickets/19894, 2024. Ethereum Research post, August 26, 2024. +[4] Jonah Burian, Davide Crapis, and Fahad Saleh. Mev capture and decen- +tralization in execution tickets. arXiv preprint arXiv:2408.11255, 2024. +[5] Vitalik Buterin. Pbs- friendly fee market design. +https://ethresear.ch/t/proposer-block-builder-separation-friendly-fee- +market-designs/9725, October 2017. Ethereum Research post, October 17, +2017. +[6] Hao Chung, Elisaweta Masserova, Elaine Shi, and Sri AravindaKrishnan +Thyagarajan. Rapidash: Foundations of side-contract-resilient fair ex- +change. In Workshop on Cryptographic Tools for Blockchains (CTB 2024). +Eprint, volume 1063, 2022. +[7] Philip Daian, Steven Goldfeder, Tyler Kell, Yunqi Li, Xueyuan Zhao, Iddo +Bentov, Lorenz Breidenbach, and Ari Juels. Flash boys 2.0: Frontrunning +in decentralized exchanges, miner extractable value, and consensus instabil- +ity. In 2020 IEEE symposium on security and privacy (SP), pages 910–927. +IEEE, 2020. +[8] Justin Drake. Mev-burn-a-simple-design. https://ethresear.ch/t/mev- +burn-a-simple-design/15590, May 2023. Ethereum Research post, May 2, +2023. +[9] Shayan Eskandari, Seyedehmahsa Moosavi, and Jeremy Clark. Sok: Trans- +parent dishonesty: front-running attacks on blockchain. In International +Conference on Financial Cryptography and Data Security, pages 170–189. +Springer, 2019. +[10] Flashbots. Mev-boost. https://github.com/flashbots/mev-boost, 2022. +Flashbot. +[11] Lioba Heimbach, Lucianna Kiffer, Christof Ferreira Torres, and Roger Wat- +tenhofer. Ethereum’s proposer-builder separation: Promises and realities. +In Proceedings of the 2023 ACM on Internet Measurement Conference, +pages 406–420, 2023. +[12] Paul Janicot and Alex Vinyas. Private mev protection rpcs: Benchmark +stud. arXiv preprint arXiv:2505.19708, 2025. +[13] Alireza Kavousi, Duc V Le, Philipp Jovanovic, and George Danezis. Blind- +perm: Efficient mev mitigation with an encrypted mempool and permuta- +tion. Cryptology ePrint Archive, 2023. +[14] Chenyang Liu, Ittai Abraham, Matthew Lentz, and Kartik Nayak. Dpaas: +Improving decentralization by removing relays in ethereum pbs. Cryptology +ePrint Archive, 2025. +[15] Bruno Mazorra, Burak ¨Oz, Christoph Schlegel, and Fei Wu. The free option +problem of epbs. arXiv preprint arXiv:2509.24849, 2025. +[16] Conor McMenamin. Sok: Cross-domain mev. arXiv preprint +arXiv:2308.04159, 2023. +[17] Mike Neuder. Equivocation attacks in mev-boost and epbs. +https://ethresear.ch/t/equivocation-attacks-in-mev-boost-and- +epbs/15338, 2023. Ethereum Research post, April 18, 2023. +[18] Alexandre Obadia, Alejo Salles, Lakshman Sankar, Tarun Chitra, Vaibhav +Chellani, and Philip Daian. Unity is strength: A formalization of cross- +domain maximal extractable value. arXiv preprint arXiv:2112.01472, 2021. +[19] Burak ¨Oz, Christof Ferreira Torres, Christoph Schlegel, Bruno Mazorra, +Jonas Gebele, Filip Rezabek, and Florian Matthes. Cross-chain arbitrage: +The next frontier of mev in decentralized finance. Proceedings of the ACM +on Measurement and Analysis of Computing Systems, 9(3):1–33, 2025. +[20] potuz. epbs design constraints. https://ethresear.ch/t/epbs-design- +constraints/18728, February 2024. Ethereum Research post, February 20, +2024. +[21] Kaihua Qin, Liyi Zhou, Pablo Gamito, Philipp Jovanovic, and Arthur Ger- +vais. An empirical study of defi liquidations: Incentives, risks, and insta- +bilities. In Proceedings of the 21st ACM internet measurement conference, +pages 336–350, 2021. +[22] Caspar Schwarz-Schilling, Fahad Saleh, Thomas Thiery, Jennifer Pan, Ni- +har Shah, and Barnab´e Monnot. Time is money: Strategic timing games +in proof-of-stake protocols. arXiv preprint arXiv:2305.09032, 2023. +[23] James Stearn. ‘cryptographic approaches to complete mempool privacy. +Flashbots Res., Cayman Islands, Tech. Rep. FRP-18, 2022. +[24] Thomas Thiery. Fork-choice enforced inclusion lists (focil): A simple +committee-based inclusion list proposal. https://ethresear.ch/t/fork- +choice-enforced-inclusion-lists-focil-a-simple-committee-based-inclusion- +list-proposal/19870, 2024. Ethereum Improvement Proposal, June 02, +2024. +[25] Francsco Thomas and Barnabe. The more, the less censored: In- +troducing committee-enforced inclusion sets (comis) on ethereum. +https://ethresear.ch/t/the-more-the-less-censored-introducing-committee- +enforced-inclusion-sets-comis-on-ethereum/18835, 2024. Ethereum +Research post, February 29, 2024. +[26] Sarisht Wadhwa, Julian Ma, Thomas Thiery, Barnabe Monnot, Luca Zano- +lini, Fan Zhang, and Kartik Nayak. Aucil: An inclusion list design for +rational parties. Cryptology ePrint Archive, 2025. +[27] Anton Wahrst¨atter, Jens Ernstberger, Aviv Yaish, Liyi Zhou, Kaihua Qin, +Taro Tsuchiya, Sebastian Steinhorst, Davor Svetinovic, Nicolas Christin, +Mikolaj Barczentewicz, et al. Blockchain censorship. In Proceedings of the +ACM Web Conference 2024, pages 1632–1643, 2024. +[28] Fei Wu, Thomas Thiery, Stefanos Leonardos, and Carmine Ventre. To +compete or collude: Bidding incentives in ethereum block building auctions. +In Proceedings of the 5th ACM International Conference on AI in Finance, +pages 813–821, 2024. From 8d05e0c71534ee8ac00ebbcdcb1c9efbfb62073c Mon Sep 17 00:00:00 2001 From: "O. Saguillo" <47833532+saguillo2000@users.noreply.github.com> Date: Thu, 18 Dec 2025 16:57:50 +0100 Subject: [PATCH 2/4] Update FRP_proposal --- FRPs/FRP_proposal | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/FRPs/FRP_proposal b/FRPs/FRP_proposal index 6425e06..9c3dc6a 100644 --- a/FRPs/FRP_proposal +++ b/FRPs/FRP_proposal @@ -10,15 +10,27 @@ created: Proposer–Builder Separation (PBS) [7][11][5], together with MEV-Boost, represents the first widely adopted approach for decoupling block construction from block proposal in Ethereum. These mechanisms have enabled a more efficient and competitive market for block building and MEV extraction [2][28][1]. However, their current realization relies predominantly on off-chain relayers, introducing non-trivial trust assumptions and creating centralization pressures -within the block production pipeline [27][11][10]. In response to these limitations, a broad spectrum of alternative designs -and protocol-level enhancements has been proposed. These include (but are not limited to) enshrined PBS [20][14], encrypted and privacy-preserving block -building [13][23][12], MEV burn mechanisms [8], execution tickets [4], execution auctions [3], inclusion lists [FOCIL, AUCIL, COMIS, etc.] [26][24][25], and -cross-domain PBS architectures [19][18][16]. Each class of design targets distinct challenges of the existing PBS model, such as reducing relayer dependence, +within the block production pipeline [27][11][10]. + +In response to these limitations, a broad spectrum of alternative designs and protocol-level enhancements has been proposed. These include (but are +not limited to): +• Enshrined PBS[20][14] +• Encrypted and Privacy-preserving block building [13][23][12] +• MEV burn mechanisms [8] +• Execution tickets [4], +• Execution auctions [3], +• Inclusion lists [FOCIL, AUCIL, COMIS, etc.] [26][24][25], +• Cross-domain PBS architectures [19][18][16] + +Each class of design targets distinct challenges of the existing PBS model, such as reducing relayer dependence, mitigating censorship and liveness risks, improving incentive alignment across participants, and strengthening security guarantees for validators and order-flow providers. + However, discussions of these designs, including their security assumptions and trade-offs are fragmented across blog posts, research articles, and forum discussions. As a result, there is no single, comprehensive resource that systematically compares these approaches or clearly outlines their shared objectives, -design trade-offs, and remaining open challenges. The goal of this project is to compile and systematize existing PBS-related +design trade-offs, and remaining open challenges. + +The goal of this project is to compile and systematize existing PBS-related designs across different layers of the blockchain protocol. The project will identify and categorize the desired properties of proposer–builder separation mech- anisms, analyze known and potential attack vectors— Sandwich attack, Frontrunning attack [7][9], Back-running attack[21], Free-option problem[15], Timing game[22], Equivocation attacks [17], Bribery attack[6], etc. , and highlight open research questions. By providing a unified framework for understanding current @@ -28,6 +40,7 @@ blockchain community. ## Plan and Deliverables The study will proceed in the following steps: + • Compile and review existing literature on Proposer–Builder Separation (PBS), including current implementations and proposed alternative de- signs related to any step in the workflow from transaction submission to block validation. • Formalize the key properties required for a secure, efficient, and decentralized block-building system. From 5503c9bde419539e7272055bd15d1ecdeae7abb6 Mon Sep 17 00:00:00 2001 From: "O. Saguillo" <47833532+saguillo2000@users.noreply.github.com> Date: Thu, 18 Dec 2025 16:58:41 +0100 Subject: [PATCH 3/4] Update FRP_proposal --- FRPs/FRP_proposal | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/FRPs/FRP_proposal b/FRPs/FRP_proposal index 9c3dc6a..389abe8 100644 --- a/FRPs/FRP_proposal +++ b/FRPs/FRP_proposal @@ -19,7 +19,7 @@ not limited to): • MEV burn mechanisms [8] • Execution tickets [4], • Execution auctions [3], -• Inclusion lists [FOCIL, AUCIL, COMIS, etc.] [26][24][25], +• Inclusion lists (FOCIL, AUCIL, COMIS, etc.) [26][24][25], • Cross-domain PBS architectures [19][18][16] Each class of design targets distinct challenges of the existing PBS model, such as reducing relayer dependence, From a597b04b97ae008f8cdf4ceeb19037748186468c Mon Sep 17 00:00:00 2001 From: "O. Saguillo" <47833532+saguillo2000@users.noreply.github.com> Date: Thu, 18 Dec 2025 17:01:01 +0100 Subject: [PATCH 4/4] Update FRP_proposal --- FRPs/FRP_proposal | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/FRPs/FRP_proposal b/FRPs/FRP_proposal index 389abe8..a25e2ab 100644 --- a/FRPs/FRP_proposal +++ b/FRPs/FRP_proposal @@ -1,7 +1,7 @@ --- id: title: SoK: Proposer-Builder Separation and Beyond -team: Oriol SAGUILLO, Prerna Prabhakar AROTE, Lucianna KIFFER (IMDEA Networks Institute) +team: Oriol SAGUILLO, Prerna AROTE, Lucianna KIFFER (IMDEA Networks Institute) created: ---