Proposer Builder Separation

ideas relay host private transaction, but epbs doesn't? would that make any difference to the performance FC REVIEW =========== -- 27/10/2025 -- Site: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcrypto.unibe.ch%2Ffc26%2Fpaper.php%2F106&data=05%7C02%7Ctammy.wang.20%40ucl.ac.uk%7C133dc2c16be246c448db08de1577378d%7C1faf88fea9984c5b93c9210a11d9a5c2%7C0%7C0%7C638971798974925008%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=mXZ4K3BiBsA1ylM1v72IJp%2F82cHfIHkrN%2FSj%2BNAd4sc%3D&reserved=0 # Review #106A ## Paper summary The paper utilized mathematical analysis and simulations to study the centralization and profit distribution of Ethereum validators and block builders under enshrined Proposer-Builder Separation (ePBS). The paper emphasized builder centralization and unequal profit distribution among builders under ePBS. ## Comments for authors Strengths - The topic is relevant to FC. - The defined research question about ePBS is timely. - The methodologies used in the paper are mostly sensible given the nature of the question studied. Weaknesses - The paper claims to study enshrined PBS (ePBS) but evaluates it primarily against pre-PBS PoS. For a credible assessment of introducing ePBS, the natural baseline is the current relay-based PBS (MEV-Boost). Moreover, it is unclear how the modeled ePBS in the paper differs materially from today’s PBS design. The scope and the baseline of the paper are therefore questionable. - Given the apparent similarity between the paper’s ePBS model and existing PBS deployments, many results seem to reiterate findings already covered by the cited paper [1], although reinforced with additional simulations. The paper’s contribution would be stronger if it isolated what is genuinely enshrinement-specific (for example, different ePBS designs such as block-auction ePBS or slot-auction ePBS, thus not covered by [1]) or provided new empirical/theoretical insights that go beyond prior PBS analyses. - Figure 4b shows that most MEV profits are captured by builders under ePBS. However, the thing is builders will have to bid that value to proposers to win the auction, so that most MEV profits should be captured by the proposer/validator, with builders retaining only the residual margin. This inconsistency further makes me question the simulation results of stake distribution presented in Figure 7. In addition, the authors’ statements like “Under ePBS, builders’ integrated revenue streams drive faster accumulation than in PoS…” and “Builder profits become highly concentrated (Gini coefficient rising from 0.1749 under PoS to 0.8358 under ePBS)…” are confusing because in the PoS baseline, there is no builder role, so it’s not clear what the authors are referring to here. Other minor comments - “Validators are randomly chosen two slots in advance from eligible participants to propose a block.” Proposers are randomly assigned at the start of each epoch, so the schedule of proposers for the next 32 slots is known one epoch in advance. - “Builders submit bids every 0.5 seconds, i.e., 24 rounds per slot [13].” There is no such constraint if I remember correctly. - “ePBS disables bid cancellation.” This is not correct. Check https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fhackmd.io%2F%40potuz%2FrJ9GCnT1C%23FAQ&data=05%7C02%7Ctammy.wang.20%40ucl.ac.uk%7C133dc2c16be246c448db08de1577378d%7C1faf88fea9984c5b93c9210a11d9a5c2%7C0%7C0%7C638971798974939917%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=6QC5IToP%2FaSxtF9m5efEEe7j5eGgEhSXaqWs%2FA1irbE%3D&reserved=0. ## Suggested improvements for Revision As mentioned above, I would suggest the authors: - Explicitly identify what is enshrinement-specific, or what is essentially different in ePBS from today’s PBS design (MEV-Boost), and see how these things impact the metrics measured in the paper - Add a baseline of current PBS (MEV-Boost) I personally don’t think these changes are feasible during the shepherding period. ## Overall merit 1. Reject ## Reviewer expertise 4. Expert ------------------ # Review #106B ## Paper summary The paper studies the effect of enshrined Proposer-Builder Separation (ePBS) on decentralization and fairness in Ethereum’s Proof-of-Stake system. ePBS is the "protocol-native version" of PBS, which separates the roles of block proposers and builders to prevent validators from manipulating transaction order for MEV. While current PBS relies on external relays such as Flashbots, ePBS integrates this process directly into the consensus layer, aiming to remove relay centralization and improve censorship resistance. The paper develops a formal model and agent-based simulation to compare standard PoS and ePBS settings. The analysis focuses on Maximal Extractable Value (MEV) dynamics and finds that, under ePBS, builder profits and block content become more concentrated, with a few MEV-seeking builders dominating auctions. The authors conclude that ePBS amplifies centralization and transaction reordering rather than mitigating them. ## Comments for authors Overall, the study is competently executed and addresses a relevant question, but the interpretation should more carefully separate what is intrinsic to ePBS from what is generic to MEV markets. A clearer causal analysis would make the results more convincing and help readers understand whether the enshrinement proposal introduces new risks or merely highlights existing ones: - The conclusion that ePBS amplifies centralization (Section 5.1) feels counter-intuitive. ePBS is designed to remove the trusted relay layer used in PBS and should, in principle, strictly improve decentralization. The results shown, particularly the strong builder dominance and the Gini increase from 0.17 to 0.83, seem to reflect general MEV-auction dynamics already present in PBS rather than effects unique to ePBS. It would be useful to clarify which part of the result stems from the auction and MEV structure versus which arises from ePBS’s specific protocol changes (for example, commit-reveal or disabling bid cancellations). - The agent-based simulation in Section 5 provides quantitative evidence but largely confirms well-known patterns, that MEV-efficient builders dominate, proposers earn fixed revenue, and restaking amplifies inequality. A comparison to the current Flashbots relay-based PBS system would make the results more grounded and reveal whether ePBS actually changes the equilibrium. - The fairness analysis (Section 5.2) links higher inversion counts to ePBS, but this appears to me that to arise from builder behavior rather than the ePBS mechanism itself. It would strengthen the argument to explain whether the auction design inherently promotes more reordering or whether it is a side effect of aggressive MEV strategies. ## Suggested improvements for Revision - Clarify the causal link between ePBS and the observed centralization effects. - Add a baseline or control experiment reflecting the current relay-based PBS system - Expand the discussion of related work to position this study relative to recent analyses of PBS and builder concentration ## Overall merit 2. Weak reject ## Reviewer expertise 2. Some familiarity AFT REVIEW ============================= -- 20/07/2025 https://arima.cylab.cmu.edu/aft25/paper.php/70 ## Comments overview - [ ] negative payoff is not allowed -- strong assumption - [x] reivewer said pbs bid is sealed -- need to check, don't think it is sealed bid auction - [ ] the simulation is too thin for the claim that i am making, should take the gas and mev from multiple time frames including highlt volatile times. - [x] all validators are economically passive is too unrealist as an assumption, they reinvest their profit and some of them also is builders them selfs -- this could be ignonred if stating this is an single epoch study - [x] need to state clearly that im comparing pos with and without pbs, not pos and pbs - [ ] Th2 prop3,4 are too stright foward intuitive result - [x] why relay is not described -- becasue we are doing ePBS, need to state clearly ## DOTO - [ ] Change all the pbs to epbs - [ ] Compare PoS with ePBS and without ePBS - [ ] Need to state early on that this study is for single epoch or short term - [x] Need to rethink how to state RQ, camparing builders with validators, how to justify the comaprison - [x] Negative payoff in assumption(only one reviewer mentioned, keep) - [ ] Validator incentive need to redesign - [ ] Hence the maths need to be updated - [ ] Simulation wise, need to fetch more data range - [ ] Need to add relay privacy and time - [ ] for the assumptions, need to justify ### Restructure of analysis - Builder centralization in the following cases, how to maximise utility when under these conditions and what is the expected outcome in the long term - Non MEV, reinvesting - MEV, reinvesting - MEV, no reinvesting - The expected long term utiltiy need to consider the auction mechanism - ## Review #70A Overall merit 2. Weak reject Reviewer expertise 3. Knowledgeable ### Paper summary The work formalizes an auction‑theoretic model of Ethereum’s PBS and combines this with an agent‑based simulation to study how MEV affects economic concentration. Analytically, the authors show that (i) with zero latency the PBS auction converges to a second‑price outcome and (ii) builders who insert MEV‑seeking transactions always realize a weakly higher private valuation than benign builders, therefore winning more often. In simulations calibrated with on‑chain gas‑price and Flashbots data, they report a dramatic rise in inequality: the Gini coefficient of profit between block‑producing agents grows from 0.1749 (PoS baseline) to 0.8358 under PBS, while ~95 % of the surplus flows to the slot proposer. Heat‑map inversion counts further indicate that transaction re‑ordering increases sharply as the fraction of malicious builders grows, implying that PBS amplifies rather than mitigates MEV‑driven centralization. ### Comments for authors The work presents a timely and well-motivated analysis of PBS and MEV concentration using a combination of auction theory and simulation. However, the underlying model makes several strong assumptions that weaken the conclusions. The private valuations in Eq. (4) assume that gas fees and MEV gains are additive and guaranteed. In reality, builders face inclusion, execution, and fork risks that introduce meaningful uncertainty. By disallowing negative payoffs in Assumption 9, the model removes downside risk entirely, making aggressive bidding cost-free. This likely exaggerates profit concentration and overstates the centralizing effect of PBS. The latency‑aware auction theorem (Theorem 1) assumes all bids propagate within 2Δ rounds, after which a English‑auction result is invoked. However PBS bids are sealed until the reveal phase and cannot be incrementally observed by competing builders; the proof therefore mixes two different auction models. It's therefore critical to revisit the equilibrium derivation: to model mev‑boost realistically, relay privacy and proposer timing leakage must be included. The empirical calibration is too thin for the bold numerical claims. Block gas limits, fee‑market elasticity and the γ‑distributed MEV sample are taken from a single three‑week window, whereas MEV intensity is highly volatile. Re‑running the simulation on several disjoint main‑net traces (e.g., Nov‑23 ↔ Apr‑24) and on outlier days (USDC de‑peg, meme‑coin surges) would show whether the 0.83 Gini is robust. Some assumptions appear unrealistic. All proposers are treated as economically passive despite mounting evidence that large staking pools are vertically integrating with builders. Ignoring re‑investment means long‑run wealth concentration is understated, contradicting the discussions in Section 8.1. It would be cleaner either to extend the horizon and let agents compound rewards or to frame the study explicitly as a single‑epoch analysis. ## Review #70B Overall merit 1. Reject Reviewer expertise 4. Expert ### Comments for authors This paper aims to investigate an important but also extensively studied problem. In comparison, this paper does not appear to contribute any strong results. Its analysis is rather weak and loose. The simulation setup appears somewhat arbitrary. Analysis: E.g., the model captures latency, but the analysis only concerns the case where $\Delta$ approaches 0. Theorem 1 basically describes an English auction. Theorem 2 says that MEV-seeking builder will bid higher and win the auctions, which is directly implied by the common mempool assumption, which is not true in practice. I don't understand Proposition 3: it seems to suggest that without PBS validators cannot get their blocks included. Proposition 4 simply states that if no one extracts MEV, then user transaction inclusion is the same, which is again an intuitive result. Overall, the modeling and the analysis only touch the simplistic cases, and the results are intuitive. Comparing PBS and PoS does not exactly make sense. PBS is a builder market system, while PoS is the consensus protocol, which takes output from PBS as input in some cases. I get that you meant to compare scenarios with and without PBS. ## Review #70C Overall merit 1. Reject Reviewer expertise 3. Knowledgeable ### Paper summary This paper studies the impact of proposer-builder separation (PBS) in Ethereum on distribution of rewards. ### Comments for authors This is interesting work, but I'm struggling to understand both the questions you're posing and the correspondence between your modeling and existing PBS dynamics. Questions: The basic research questions in this work, RQ.1 and RQ.2, are aimed at the difference between PBS and PoS. I have no idea how such a difference would even be defined, as PoS Ethereum has always had PBS-like infrastructure. Even setting this aside, pre-PBS PoS had agents extracting MEV (through priority gas auctions). Similarly, what's meant by RQ.1.2: "How does the profit distribution differ between builders and validators under PBS and PoS"? There are no builders in PoS without PBS. So I have no idea what this question is asking. Modeling: This paper glosses over key entities in PBS—searchers and relays. That would be fine if appropriately justified. But the lack of understanding about how relays work introduces some bizarre assumptions, like discrete, 1/2-second bidding rounds, with bids transmitted among builders (in a network model that doesn't correspond to real PBS). Other incorrect assumptions include transparency of transactions (some come from private order flow), the idea of malicious transactions coming directly from end users (an outmoded arbitrage modality), etc. None of this matters in the end, Theorem 1 is cast in a way that degenerates into a simple English auction, while Theorem 2 includes an entity, a "non-MEV-seeking builder," that in no way reflects real builder behavior. In summary, PBS is a complex, rapidly evolving piece of infrastructure and the subject of intense scrutiny and study by industry participants. To do useful research on it requires either intimate familiarity with the nuts and bolts—something that can't be derived from research papers alone—or carefully crafted and justified abstractions. The authors are tackling critical questions. I'd urge tham to reformulate their model in a way that is better informed by the on-the-ground realities of PBS. ## Review #70D Overall merit 2. Weak reject Reviewer expertise 3. Knowledgeable ### Paper summary The paper uses mathematical models as well as simulations to analyze Ethereum's Proposer Builder separation. The main message of the paper is that the competitive auctions process included in PBS incentivizes aggressive MEV-extraction policies that ends up concentrating power among the most sophisticated builders. This ways it centralizes centralization and inequality amongst block builders. ### Comments for authors Overall, this is a timely paper on understanding the effects (benefits/drawbacks) of PBS to decentralization. The results do not feel particularly surprising given the modeling assumptions (e.g. the mathematical results feel rather straightforward) but I could imagine this type of work inspiring more advanced follow-ups. The experimental results are probably the most interesting elements of the paper. Finally, some elements of the paper feels rushed. For example, the misplaced abstract is a clear such indication. Some non-exhaustive list of typos include: Page 6: The word "exchanges" is misspelled as "exchangess". Page 8: "Attribute" is misspelled as "atrtibute". Page 19: Divination ----------- Some Thoughts: - user case transaction independence: can you really say the transaction inclusion is completely independent of auction win? if the gas fee is higher then is it will effect the auction result no? But the transaction is sent to a lot of builder s, will this gas fee effect be neglegble? how can i porve this rigrously? but... does P(txinclusion) already inclde the gas fee factor etc, it is the propbability of being selected in a block for any validaotors, so it should be the same for being selected by any builders. TODO: - [x] Notation for game sapce (do I actually need this?) graph, and gas - [x] Strategy notation s and sigma - [x] Notation for user and utility - [x] Cite for bidding - [x] Illustration improve: agents and facilities different, remove the unnessasry rectangles - [x] Searchers not defined - [x] Pure strategy? - [x] t for v_i? - [x] is bid b_i and strategy sigma_i the same thing? - [x] Expected value for mev inclusion probability EC REVIEW ============================= -- 27/03/2025 https://ec2025.hotcrp.com/paper/416 TODO: - [x] G-i dependent on builder actions ## Review #1 ### Paper summary This work investigates Proposer-Builder Separation, a market-based solution for Ethereum validators to outsource the construction of their blocks to sophisticated entities known as Builders. The paper intends to study the auction via which this separation occurs, as well as the ability of builders to extract MEV and thus increase their competitivity in the auction. Simulations are further presented. ### Strengths and Weaknesses The paper is really below the bar. The model does not represent the practice well, and its "theorems" are either ill-posed or trivial; it is said in the abstract that a finding is about censorship under PBS, but this is never explored; the simulations do not capture interesting phenomena; other (non-cited) papers have done a better job with these results than this paper (e.g., Capponi, Jia, Olafsson 2024 "Proposer-Builder Separation, Payment for Order Flows, and Centralization in Blockchain"). ### Comments for authors "This fundamental shift to PoS raised challenges and concerns related to Ethereum’s consensus mechanism, such as MEV, transaction censorship, and centralization under the more powerful validators." => This is vague, in particular there is nowhere in the text that makes the case for why PoS systems should be more concerned about these issues than PoW systems. CoW protocol is referenced in backrunning, but this is unclear that this is the essence of CoW. Solvers in CoW may backrun to offer profits to the user, but that is one of many alternatives they have. "if a validator sees the MEV available in a block significantly exceeds the standard block reward they may be incentivized to reorganize blocks and capture the MEV for themselves, which can cause consenses instability." => I would cite Daian here https://arxiv.org/abs/1904.05234 Figure 1 is quite misleading, it would be much better to decompose between base fee (paid to the network) and MEV (which includes priority fee). Why does the (consensus) block reward factor in this? The decomposition between gas fees and MEV in the model is then unclear. The proof of Theorem 1 is simply the proof of bidding in second-price auctions? Why all the formalism of multiple bidding rounds then? Not sure why a user needs to be able to send many transactions, vs have each transaction be sent by a single user. "For non-MEV builders:" => This is an artefact of the model, where MEV is a fully separable quantity, which it is not (it is order-dependent, and can be expressed to a builder, even to one that passively ranks by highest priority fee). Theorem 3: P(win|MEV) is this always less than or equal to 1? m is unbounded (also rather ill-defined), so I don't see a reason this holds. ## Review #2 ### Paper summary The paper studies PBS and its effect on centralization. It claims prior work on the topic is mainly based on empirical data and lacks formalization, motivating this paper’s attempt at providing a theoretical framework. The model includes users, builders and proposers participating in the PBS pipeline. There are some theoretical claims about centralization and inclusion probability with and without PBS, as well as simulations. ### Strengths and Weaknesses The topics of MEV, PBS and centralization are important. However, the paper lacks formalism, and there are many issues with the model and analysis. As such, it does not deliver on the promise of introducing a “comprehensive theoretical framework” for understanding PBS dynamics. Some example of lack of rigor: Theorem 1 talks about Bayes-Nash Equilibria of the builder auction, without mentioning priors. Theorem 2 and its proof are descriptive statements. The argument that PBS is centralizing is that “repeated successes of MEV builders in being selected for block proposals can lead to a feedback loop, where their accumulated profits from MEV allow for even more aggressive bidding strategies, further entrenching their competitive edge.” Note that this particular dynamic was in fact studied rigorously in prior work [Bahrani et al., 2024], which the author claim lacks theoretical backing. ### Comments for authors Definition 1 seems to suggest searchers can only try to affect their transaction’s position by adjusting the gas fee of their new transaction’s gas fee. In practice searchers submit “bundles” that include other users’ transactions plus any new transactions, and the whole bundle must be included contiguously. Definition 1 “When a user 𝑈𝑖 initiate a transaction without targeting for MEV profits, and simply broadcast this to its peers.” → what is meant by “peers” here? Other users? Builders? Validators? The gas fees in a block go to the proposer, not the builder. Definition 5 claims the builder collects gas fees. In Definition 8, G_i should depend on the actions of builders (different blocks pay different gas amounts). Its distributions should therefore also depend on the actions of builders. This also applies to definition 9. "non-MEV builders" -> this doesn't exist in practice SNP REVIEW ============================= -- 20/01/2025 https://cycle2.sp2025.ieee-security.org/paper/1018 TO-DO ================ - [x] Main aim should not only be mev (still discuss mev but reduce its appearnce) - [x] Need to add discussion in the end including: - [x] camparison to existing research especially on emperical - [x] discussion on different aspect builder proposer user - [x] validator centralization with reinvesting the profit - [x] Clarify how network latency is implemented using visible builders - [x] Clarify section 4.3 ## Review #1 ### Paper Summary ------------- This work explores the Proposer-Builder Separation (PBS) scheme of the Ethereum protocol which defines a framework for splitting those who put together transactions into a block (the builder) from those that add it to the blockchain (the proposer/validator in PoS). The authors explore the dynamics between these two types of players and users who generate transactions in an agent-based model (ABM). The main motivation of the analysis is an exploration of the inclusion of MEV transactions (viewed as attack transactions in this work, which gain more utility from inclusion). The main findings of the work is that there is more incentive in PBS for MEV inclusion and a centralizing tendency for builders who include MEV transactions. ### Technical Correctness --------------------- 3. Fixable Major Issues ### Scientific Contribution ----------------------- 6. Provides a Valuable Step Forward in an Established Field ### Presentation ------------ 3. Major but Fixable Flaws in Presentation ### Comments to Authors ------------------- The work I think is a nice step towards a more formal analysis of the block-building ecosystems and the players involved. These are complex, heterogeneous systems and therefore complicated to model/ be able to prove properties about. My main criticism of the work is three-fold: 1.) First, the motivation for the main result is that PBS is a mechanism to thwart MEV/ increase builder decentralization. From my understanding, there is nothing in PBS meant to stop MEV, it is actually based on the original flashbots implementation which worked to give an auction structure for MEV bundles. The main point is to more fairly split the profit among the proposers by giving them all access to profitable blocks built by good builders. This competition implies the good builders have access to MEV. 2.) There is some formalism missing in the paper. Primarily, it would have been nice to first formally state properties that PBS or PoS should satisfy, e.g., what is meant by "centralization/decentralization" etc. Also, some of the theorems (e.g., theorem 1) are not formally written (e.g., "This advantage [...] potentially leads to a market dynamic fostering centralization...") and then the proofs read more like a hand-wavy discussion. It would be more impactful to mathematically state the properties you are proving and disproving and use these in the theorems/proofs precisely. 3.) While there is good discussion of the results presented in the simulations, I am not convinced by the setup. For starters, there is a good amount of detail missing e.g., (A)what is the bidding strategy of the builders? This, I imagine, has a big impact on who wins. (B) details on the networks of the simulations, like where does delay come into the actor choices and what is the structure of the underlying network/ how is connectivity implemented? etc. Also, some assumptions don't fit well with reality e.g., in PoS validators who can build better blocks would then reinvest this in stake and become more centralized, this is not captured. Also that the builders keep the majority of MEV profit, previous work has shown that this profit actually primarily goes to the proposer. I would also be careful with how much of the larger takeaways of the simulations are dependent on the parameter choices. Other smaller points: - I don't follow the arguments in section 4.3. First it states that MEV gives a block a competitive edge, to get thm 2. This implies that MEV transactions influence whether a block is chosen. Therefore I don't follow the argument for transaction independence, it would seem that MEV transactions also have a competitive edge and their inclusion probability is not the same as regular transactions. - Fix the references, currently without links, the majority of the references are worthless because its impossible to find the actual source. Also, for those that are papers, quite a few are missing the conference information. - The paper touches on block bidding strategies but fails to reference work in this space, e.g., the FC'24 paper by Bahrani et. al. "Does Proposer-Builder Separation Preserve Decentralization", and others ### Recommended Decision -------------------- 4. Reject ### Reviewer Confidence ------------------- 2. Highly Confident ### Should this submission be reviewed by the Research Ethics Committee? -------------------------------------------------------------------- 1. No ## Review #2 ### Paper Summary ------------- The paper analyses the implications of MEV by comparing PBS against PoS by applying a theoretical analysis and agent-based modeling. The work aims to answer the questions whether PBS increases decentralization as compared to PoS, what is the effect of PBS on the ordering of MEV transactions, and how are costs as well as profits distributed between PoS and PBS. The theoretical findings indicate the PBS does not increase decentralization and that it promotes MEV extraction. ### Technical Correctness --------------------- 3. Fixable Major Issues ### Technical Correctness Comments ------------------------------ The evaluation presented in the paper does not provide any novel insights as compared to already existing empirical studies. In general, the paper is missing a comparison between the results obtained via the simulation and the results measured in the real-world by past works. Finally, the results presented in the paper seem rather biased towards providing evidence that PBS fails its goals in decentralizing block building and as well as profit distribution. ### Scientific Contribution ----------------------- 1. Independent Confirmation of Important Results with Limited Prior Research ### Scientific Contribution Comments -------------------------------- The paper presents a mathematical analysis and leverages agent-based modeling to simulate MEV extraction under different number of MEV extracting users, builder and validators. The analysis presents an opportunity to validate and compare to real-world results that have been extracted using past empirical studies. ### Presentation ------------ 2. Minor Flaws in Presentation ### Presentation Comments --------------------- Overall the paper is well written and easy to follow and contains only a few typos. However, Figures 3, 4, 5, and 6 have a very low resolution where the text withing the figures is barely readable. I suggest that the authors increase the font-size of the text or represent the results differently. ### Comments to Authors ------------------- Overall, it is unclear why a simulation is useful when a significant number of previous works already analyzed the problem of cost distribution and decentralization across PBS using even empirical data that is based on real-world transaction data. A better explanation and motivation what benefits a simulation can provide in contract to the existing empirical studies would be valuable. Moreover, given that numerous works have already analyzed whether PBS achieves its goals, when evaluating the results, a comparison with these works would be expected, however, the evaluation section is missing such comparisons that would help understand whether the simulation agrees with the observed results in past studies or not. Finally, the paper seems very biased towards highlighting that PBS does not achieve its goals and that PoS seems to be doing better, which I do not agree and argue it depends on which party (e.g., user, builder, or proposer you focus). For instance, PBS was created not with helping builders in mind but rather validators/proposers. With the block reward being removed validators are only left with transaction fees or MEV as a source of income. However, in PoS, MEV extraction is very centralized, because in the end validators are left alone with extracting MEV, meaning that only validators which are keen and experts with extracting MEV will be able to extract MEV and also make more profits and hence MEV extract will be centralized towards a set of validators. However, with PBS MEV extraction is distributed across validators, independently of their knowledge in extracting MEV, since block builders will do this job for them, independently whether the validators/proposers are experts in MEV or not. However, block builders will naturally suffer from centralization. Thus, decentralization depends on the perspective, while PBS creates decentralization amongst builders, it creates decentralization amongst validators, which is something PoS does not achieve. This insight has been proven in empirical studies but is not mentioned or highlighted in this paper. Another aspect is the profits dynamic, which I also do not agree. Yes, builders make more profits that users, and in PoS users make more profits than PoS. However, the later is only if private pools are ignored, which is unrealistic. Besides that, in the case of PBS, previous works have shown that a significant amount of the profits that builders make, they have to give it further to the proposers as otherwise they will not decide to include their blocks. Also this is natural, the only parameter that builders can leverage to tweak whether the current proposer takes their block instead of the block of a competing builder is because their block returns more value and the easiest way to do this is by letting the proposer get a big portion of the builders own profit. While this has been measured and observed in empirical past studies, the paper does not mention anything around this observation and in the context of PBS only talks about users and builders. However, to conclude, PBS was not designed with builder decentralization in mind, but rather as a mechanism to keep validators incentivized to propose blocks and stake even in the event where block rewards do not exist anymore. From a validator perspective, PBS leads to more profits for validators and also a decentralized distribution of profits. ### Recommended Decision -------------------- 4. Reject ### Reviewer Confidence ------------------- 1. Certain ### Should this submission be reviewed by the Research Ethics Committee? -------------------------------------------------------------------- 1. No TO-DO ================ - [x] Explain the parameters - cite for justification - [x] Why use Gamma distribution - [x] Timeframe of the sample gas fee selection - [x] Make sure all RQ are answered USENIX REVIEW ======================================================== -- 15/10/2024 https://sec25cycle1.usenix.hotcrp.com/paper/1162 ## Review #1 ### Paper summary The paper compares the paradigms of Proposer-Builder-Separation (PBS) and regular Proof-of-Stake without PBS. It takes a game-theoretic/agent-based approach and provides a formal analysis and simulations. One of the findings is that PBS might even increase MEV extraction. ### Main reasons to accept the paper The paper proposes a formalized model for PBS The evaluation suggests novel insights, e.g., that PBS might even increase MEV ### Main reasons to reject the paper Assumptions and parameters not all well-justified Research questions are a bit disconnected from evaluation ### Comments for authors #### Comments Justification of assumptions and parameters Overall, I found that while the paper strives to provide a realistic model and simulation of PBS and PoS, many of the assumptions and parameters are not well explained. Since the realism of this study is what the relevance of the results hinges on, this is my most important concern. Section 3.1 of the paper lists twelve assumptions of their formalization. While most of those seem intuitive or realistic, no detailed justifications are given (and only assumption 8 is justified by two citations). The paper should discuss in more detail if and how these assumptions are realistic. Similarly, the paper claims to select "parameter values that are grounded in reality" but does not go into much more detail. Definition 8 and 9 propose the use of Gamma distributions for gas fees and the MEV profit. However, there is no discussion for why this type of distribution was chosen. Section 5.3 mentions that the parameters for the distribution were selected from historical data but does not mention the timeframe and method of extraction. For example, how were MEV transactions identified? The other parameters mentioned in Section 5.3 appear to be chosen arbitrarily. Are 20 users, 50 builders, and 50 validators realistic? What about 50 transactions per block? How and why were these parameters chosen? Definition 12 (Transaction Independence) is not well-justified either and would benefit from a clearer discussion and justification. #### Unclear setup Some parts of the setup/model are a bit unclear and introduced only late in the paper. For example, the possibility of non-MEV users is first explicitly covered in Section 5.1 of the simulation design. For builders, this distinction is made much earlier in Section 4.2. This makes it hard to follow the model and creates surprises at a later point. #### Research questions I really appreciate the concrete list of research questions in Section 1.1. However, the paper does not make it easy to find the corresponding answers in the evaluation. Section 1.1.1 is covered in Section 6.1 and Section 1.1.3 is covered in Section 6.2. The questions from Section 1.1.2 are a bit lost, especially since transaction ordering is only mentioned in very few places of the paper. #### Minor comments Section 6.1.1, the first reference to Figure 4 should reference Figure 3 instead Figure 3/4, the labels of plot (b) are cut Section 6.1, "mev" instead of "MEV" The paper states that it is "moving beyond empirical studies", but one of the main results, the simulation, is in principle an empirical result. ### Recommended decision 4. Reject ### Confidence in recommended decision 2. Highly confident (would try to convince others) ### Ethics consideration 3. No (risks, if any, are appropriately mitigated) ### Open science compliance 1. Yes. ### Questions for authors' response How did you come up with the parameter choices and how were they grounded in reality? ## Review #2 ### Paper summary The paper examines the PBS mechanism in blockchain systems, specifically Ethereum. It assesses PBS’s effectiveness in mitigating MEV risks compared to the traditional PoS mechanism. The study leverages mathematical analysis and agent-based simulations to explore how PBS influences transaction inclusion, profit distribution, and the strategic behavior of network participants. Through these methodologies, the paper provides insights into the operational dynamics of PBS and its impact on the overall blockchain ecosystem. ### Main reasons to accept the paper More actionable suggestions than Heimbach et al. [16] Provides a strong foundation for future research and optimization of blockchain mechanism ### Main reasons to reject the paper Oversimplified assumptions Doesn't address relay reliability and trustworthiness in depth compared to [16] ### Comments for authors I was a bit worried at first that this paper might be too similar to [16], but after going through it, I can see it actually dives deeper into the theoretical framework, methodology, and offers specific ideas for improvement. It goes beyond [16], which mainly focuses on identifying the challenges and open problems around PBS. This paper seems to provide a solid base for future research and improving blockchain mechanisms. That said, [16] does a great job of highlighting important issues like builder and relay centralization, PBS’s role in censorship, and relay trustworthiness. While this paper covers most of those, it doesn’t dig into the trustworthiness and reliability of relays as much. Instead, it hints that separating roles in PBS could introduce new dynamics that impact trust, which adds a fresh perspective but leaves some gaps. So, while this paper definitely builds on [16] and pushes the conversation forward, I’m not totally convinced its framework is more than an incremental improvement. It’s moving in the right direction but might not fully address all the key concerns from [16]. The paper assumes that the inclusion of any single MEV transaction does not significantly alter the likelihood of a block winning auction. However, does this always hold true? Can network conditions influence transaction inclusion? For example, network latency may delaye the transaction in propagating across the network and the transactions will be included in blocks later than expected. Could this effect be confused with that of front-running? How does the paper account for that? ### Recommended decision 4. Reject ### Confidence in recommended decision 4. Not confident (would be convinced by different opinions) ### Ethics consideration 3. No (risks, if any, are appropriately mitigated) ### Open science compliance 1. Yes. ### Questions for authors' response Why doesn't the paper explore relay reliability and trustworthiness in more depth? Can you explain the specific trust risks or benefits of separating roles in PBS? How do network conditions, like latency, impact the inclusion of MEV transactions and potential confusion with front-running? SIGMETRICS REVIEW =========================================================================== -- 26/03/2024 ## Review #1 ### Overall Merit - Reject (15-30%) ### Reviewer Expertise - Some familiarity ### Paper Summary The paper conducts a theoretical evaluation of the Proposer Builder Separation (PBS) mechanism and its impact on addressing the issues associated with Maximal Extractable Value (MEV) exploitation. The theoretical results are counterfactual, indicating that instead of diminishing the problems of MEV, the PBS mechanism may not effectively reduce censorship and could inadvertently encourage builders and proposers to engage more actively in exploiting MEV opportunities. ### Weaknesses - The assumptions are too strong and lack comprehensive analysis or explanation to support the claims of this article. - The writing needs to be further polished, especially the definitions or equations. - Lack of connection between Sections 3 and 4, especially for utility definitions. ### Comments for Authors I appreciate the theoretical analysis provided in this work. The results are intuitive and interesting. However, this paper still includes the following limitations. 1. **LaTeX Formatting**: The LaTeX format of this paper is not correct. Please double-check the format. 2. **Model Simplifications and Assumptions**: - The authors employ significant simplifications and assumptions to examine the underlying equilibrium, notably modeling MEV $M$ and gas cost $G$ as linear functions of random variables $X_i$ and Weiner processes. However, there's a lack of justification for these substantial assumptions. - A deeper analysis of the effects of these functional designs would be beneficial. It also raises the question: would employing different types of modeling functions lead to the same result? 3. **Clarification Needed on Equation (16)**: The reviewer was confused about the simplified results shown in Eq. (16), particularly questioning why the authors omitted the variable $W(t)$. The reviewer acknowledges understanding that $W(t)$ becomes constant for a given time slot $t$, yet seeks further clarification from the authors. 4. **Utility Definitions**: - The authors repeatedly define the utilities of users, builders, and proposers, yet the relationship and distinctions between these definitions in Sections 3 and 4 are unclear. - The definitions provided in Section 3 appear not to contribute significantly to the rest of the paper. 5. **Writing and Definitions**: - The writing needs to be further polished, especially for the definition or equations. For example, the authors fail to explain the network available MEV() in Eq. (1). What is the meaning of Eq. (3)? - Besides, the authors explain the term $\frac{1}{(1+r)^j}$, however, this term does not show in Eq. (2) or Eq. (3). Then, in Eq. (10), the authors also redefine $B_i$. --- ## Review #2 ### Overall Merit - Strong reject (>30%) ### Reviewer Expertise - Knowledgeable ### Paper Summary The Ethereum ecosystem's introduction of the Proposer-Builder Separation (PBS) protocol aims to separate block building from proposing, which is a significant transition from Proof-of-Work to Proof-of-Stake mining. This paper examines PBS through system dynamics simulations. ### Strengths and Weaknesses **Strengths**: - The game theoretic analysis of the financial games introduced by PBS is well-motivated. **Weaknesses**: - The paper inaccurately states PBS's main goal as a countermeasure to Maximal Extractable Value (MEV) exploitation. In reality, PBS aims to democratize access to MEV rewards. - The description of PBS lacks detail, especially concerning the role of the relay and the full dynamics of MEV transactions. - The simulation details, including the implemented builder strategies, are insufficiently described. ### Comments for Authors PBS's intended goal is not to eliminate MEV but to democratize access to MEV rewards by ensuring equal opportunities for block inclusion and access to MEV rewards. The paper should accurately reflect PBS's objectives and provide a more detailed description of PBS, including all components and their roles. Furthermore, the analysis would benefit from a clearer definition of roles, assumptions, and a comprehensive description of the implemented simulation. ## Review #3 ### Overall Merit - **Merit**: Reject (15-30%) - **Reviewer Expertise**: Knowledgeable ### Paper Summary This paper provides a theoretical examination of the Proposer-Builder Separation (PBS) mechanism in the Ethereum system, aimed at mitigating the Maximal Extractable Value (MEV) exploitation threat. Unlike most studies that rely on empirical data, this paper leverages game theory and agent-based modeling to analyze the PBS design, contributing valuable insights into the mechanism's effectiveness. ### Strengths 1. The problem is well-motivated and relevant to current blockchain technologies. 2. Offers an interesting perspective on studying the PBS mechanism using theoretical frameworks. 3. The paper is well-organized, making it easier to follow the argumentation and analysis. 4. Provides a thorough background on PBS and MEV, which sets a solid foundation for the study. 5. Concludes with findings that could be valuable and interesting for further research in the field. ### Weaknesses 1. **Technical Clarity**: The technical sections, particularly Section 3, lack clarity. Notations and equations are introduced without sufficient definitions or explanations. For example, the utility functions for users are inadequately explained, and notation such as `f_i` in Equation (4) is introduced belatedly. 2. **Structural Connections**: The linkage between Section 3 and Section 4 is ambiguous, with inconsistencies in the definition of user utilities and builder utilities across equations. 3. **Consistency of Notations**: The use of notations like `U_i` is inconsistent, causing confusion between the payoff of player i and user I. 4. **Justifications and Definitions**: The paper does not adequately justify the specific forms of `Gi` and `Mi`, nor does it clarify the basis for the Nash equilibrium conditions. 5. **Game Analysis Limitation**: The analysis in Section 4.3, which focuses on a game between two players, feels incremental due to its limited scope. 6. **Novelty and Simulation Details**: The novelty in the simulation approach is limited, with only a synthetic setting considered. Furthermore, the paper lacks detailed evaluation and analysis of the simulations. ### Comments for Authors The paper would greatly benefit from aligning its game theoretical analysis with empirical data from existing literature. Such a comparison could enhance the credibility of the theoretical findings and provide a stronger argument for the paper's conclusions. DSN REVIEW =========================================================================== -- 28/01/2024 ## TODO DSN - [x] Improve formalisation - [ ] The actions should include more detailed effect to the environment, not just what variable it effects. - [ ] There should be more than two actions - [x] Undefined variables - [x] Supply demand curve should be clarified of why it could be modelled like this, or deleted as it is not used - [x] Explain why user utility is negative - [x] Describe the probability distribution of P of inclusion/acceptance - [ ] Make sure the conclusion is logically sound and derived from the results - [ ] MEV function needs more explaination ## Review #1 ### Recommended decision Reject ### Paper summary this paper addresses the context of blockchain networks based on the Proof of Stake protocol, with specific reference to Ethereum. The work focuses on cheating mechanisms enabled by the concentration of responsibilities for building and proposing blocks, and aims at evaluating the effect of their separation (known as Proposer Builder Separation - PBS). To this end, the paper advocates joint usage of game theory and Agent Based simulation, with the aim of providing an explainable interpretation on results appearing in empirical studies and to provide insight on dynamics enabled by enforced mechanisms. ### Reasons to accept intriguing connection between Game Theory and Agent Based Simulation, well suited for the context of blockchain networks ### Reasons to reject better developed in the comments for authors ### Comments for authors The subject is relevant and timely, with a significant footprint on the side of dependability. Presentation should be better organized and locally developed to make the reading less laborious for a wider potential target audience. The treatment could be developed with much better order and less assumption on the specific background on blockchain literature. Indeed, this work might be of interest also for readers interested in game theory or agent based Simulation. In several points, the work lacks sufficient formalization. For various definitions, the discoursive description remains ambiguous. The limit becomes even more relevant under the declared aim of developing the problem in a formalized approach. Moreover, discoursive presentation and various concepts out of order also hurdle a sharp distinction between what is an assumption made in this particular study about an hypothetical scenario of operation, what is shared with some segment of the literature, and what is in the actual or prospected operational practice of some blockchain network. The aim of connection between Agent based Simulation and Game Theory remains in the end unfulfilled, and also the final interpretation of results does not sufficiently fulfill the aim of achiving expleinability and insight of mechanisms that produce an emergent behaviour. Some specific points from where these limitations can be attacked include: in the background section, a system model might identify roles and responsibilities in the operation of a blockchain. In particulare, the roles of users, proposers and builders, now appearing in Sect.III might be moved here. The sequence diagram in Fig.1 is not much useful. Section III is where the treatment breaks, and it where improvement of the work might restart from. The definition of rationality should be a cornerstone to enable game theoretical development. Instead, it apepars briefly, with insufficient formalization or anticipation of where soemthing will be formalized. at this passage various questions arise: how is the utility measured? do the choice maximizes the utility or the utility that the user can predict? how is the reward measured, and with what kind of performance indicator? In Eq.(1) I miss a definition of the individual terms of the tuple (or, at least, a note that tells what will be formally specified later on) Similarly, in Eq.(2) how are g_i', u_j', f_k', \csi' defined? indeed, this is the essence of the definition of the action semantics. Written this way, the equation tells only which components of the state are affected by the action, without specifying the quantitative change. The same applies to Eq.(3). At the end of Sect.IIC, I have a doubt: are there only 2 actions in the overall system model? In the previous description I saw many more. In Eq.(4), how is the conditioned probability evaluated or estimated? More specifically, how is the dependence of \calP on the fee estimated? this is a crucial point in quantitative analysis of the behaviour over time of a blockchain. Moreover, why is the utility a negative value? How is \xi defined? will there be some assumptions, or is this based on some experimental results in the literature, or on the real practice of some blockchain? moreover, what is the discount rate r? and why does the user utility depend on the block number j? In Eq.(6), how is k defined? And, anyway, how is this equation motivated? is this an assumption of this study or is it based on some well-known mechanism? How is \xi_j defined? Later on, at point 4): how is the penalty for missing blocks defined? or, at least, on which parameters will it depend? Eq.(8) is perhaps related to the problem of estimating how is the probability of acceptance dependent on the priority fee? If this is the case, the answer should arrive earlier, or be anticipated, and developed to understand what is the actual shape of this dependence. Eq.(9) is there some ground that supports the assumption that the supply curve can be modeled this way? Or is this an assumption in an hypothetic scenario where this study is positioned? Section IV is really too much discoursive and based on ambiguous and unsupported claims. The overall treatment is develope din 10 pages, out of 11 that were available. In positive, this means that more arguments might have been provided. ## Review #2 ### Recommended decision Reject ### Paper summary The authors proposed a game theoretical framework and to analyze Proposer Builder Separation (PBS) mechanism in Ethereum. In PBS, creating the blocks is separated from proposing the blocks by forcing the proposers to choose and propose a block from a list of available blocks. This authors show that this Separation does not necessarily reduce Maximal extracted value (MEV), i.e. additional utility gained through frontrunning and other attacks. The authors also used Agent-based modeling to simulate and analyze PBS. ### Reasons to accept - MEV is a relevant problem in this space, and it is important to show that PBS may indeed not solve this issue. - The problem is complex including many different actors and aspects and a game theoretic model would be useful for this and further analysis. ### Reasons to reject - To many details in model and simulation are missing. - The shown results are not very interesting. ### Comments for authors This is an interesting problem and promising approach; however, I had significant difficulties understanding the paper. Generally, I wonder if your model might be too complex. Is it really necessary to model users and their transactions to study PBS? - A game theoretical analysis typically includes defining a set of players and a strategy set. You define users, builders, and proposers, but it is unclear if these are all players. You define actions, but there are no actions for proposers. Also, it is unclear when actions are taken. Do you assume some round-based model or continuous time? How is that handled in your simulation? - Some functions in your model are not defined, especially $\xi$ - Equation (7) does not match its description in the text. - I would expect more precise results from analysing the model, i.e. saying which strategies may provide better utility. And under which parameters. - It is unclear how the simulation is initialized. What parameters are used? For example, how do users derive fees from their discount factor? - Since the paper focuses on MEV, it would be good if MEV would be evaluated in the simulation. ## Review #3 ### Recommended decision Reject ### Paper summary The paper studies the behaviors of nodes in Ethereum. First, the payoffs of the actions are represented by a formula. Based on the formulas. simulations are performed. ### Reasons to accept - The topic is new and sounds interesting ### Reasons to reject - The rationale behind the proposed model is not clear - No game theoretical techniques have been utilized, at least in a useful way - There is no tangible relation with dependable systems ### Comments for authors The topic, namely, the MEV attack and its countermeasure, is new and sounds interesting. I believe that this problem deserves further research. On the other hand, the approach presented seems to have much room for improvement. First, as far as I saw, no game theoretical analysis has been conducted, in contrast to what the paper title implies. For example, the paper says “A key aspect of this analysis is identifying Nash equilibria in the game,...” But no such analysis is presented. (I do not consider the intersection of the demand and supply curves to be a Nash equilibrium.) Second, the payoffs of actions are represented using many parameters, but how to determine the values of these parameters was not addressed. The simulation runs should have used specific values for the parameters, but no clues are presented about them. As a result, the correctness of the simulation results remains uncertain. In the modeling, the effects of MEV attacks are represented as parameter xi. However, almost nothing is said about how to determine it; hence, it is unclear whether these attacks or mitigation measures were actually taken into account in the simulation. Consequently, the relevance of the study to the field of dependable systems has become rather limited. USENIX REVIEW =========================================================================== -- 28/11/23 ## Review #1 ### Recommended decision Reject ### Paper summary This paper analyzes the effectiveness of the proposer builder separation mechanism in mitigating maximal extractable value risks based on game theory and an agent-based simulation for blockchain systems. Simulation results indicate that the proof-of-stake consensus fails to reduce the censorship for builders and proposers. However, the contribution of this paper is not clear. In addition, some details of the proposed analysis framework and simulation results are not comprehensive, such as the agent-based simulation settings and results. ### Detailed comments for authors 1. What is the advantage of the proposed game-theoretical framework for the analysis of the proposed builder separation mechanism? And what is the contribution of this paper? Provide more details about the game-theoretical analysis in the paper. 2. The term 'user balance' in Section 3.2 is not clear. Please provide more details of 'user balance'. 3. What is the meaning of \delta in the user initiation transactions? 4. How does the builder apply the punishment mechanism for missing blocks function in Section 3.3.5? 5. How does network participants know all node are honest in Section 4.2.2? 6. How do the simulation results illustrate the dynamic interplay of incentives within the PBS framework? 7. How does the agent-based modeling assess the effectiveness of PBS? Provide more details about the agent-based modeling approach. 8. Provide more simulation results or theoretical analysis to prove that the inclusion time has a positive correlation with the priority in Section 4.2.1. 9. Provide the profit distribution using all honest nodes and the most profitable block selection. 10. The last two paragraphs require more analysis or simulation in Section 4.2.3. For example, why does the PBS mechanism introduce additional complexity and potential risk? ### Required changes 1. The structure of this paper is incomplete, and some sections such as the introduction appear missing some content. For example, the final section contains only the word "contribution". 2. The majority of the paper is devoted to describe basic knowledge and background but lacks the details of the game theory-based analysis framework. 3. The conclusions in Section 4.2.2 require additional analysis or simulation results. For example, provide the analysis or simulation results to show that the blind bidding in the PBS introduces additional complexity and risk. ### Reasons to not accept the paper 1. The paper provides an analysis framework for proposer-builder separation but lacks detail regarding the game model. Additionally, the simulation results are overly simplistic. 2. The structure and presentation of the paper are difficult to comprehend. 3. The contribution of this paper requires amplification. 4. The simulation results fail to substantiate the paper's conclusions. All conclusions in this paper should include additional simulations or experiments. 5. The related works are not comprehensive, and this paper needs to add more related work about game theory and agent-based simulation. ## Review #2 ### Recommended decision Reject ### Paper summary This paper presents a game-theoretical and simulation-based analysis of the Proposer Builder Separation (PBS) mechanism in Ethereum's blockchain, focusing on its impact on Maximal Extractable Value (MEV) exploitation. The study uses a combination of theoretical models and agent-based simulations to investigate how PBS affects the behaviours and incentives of block builders and proposers. It finds that while PBS addresses certain aspects of MEV, it does not fully mitigate the risks of transaction censorship and manipulation. The paper highlights the complex interplay of incentives in the blockchain ecosystem and suggests that PBS, in its current form, might not be sufficient to ensure fairness and security in transaction processing. The findings point to the need for further research in balancing different objectives within blockchain networks. ### Detailed comments for authors While the paper offers important insights into the Proposer Builder Separation (PBS) mechanism in the Ethereum blockchain, there are several areas that require improvement: 1. Inadequate references in Introduction and Background section: The background sections discussing PBS and Maximal Extractable Value (MEV) are lacking sufficient references. To establish credibility and context, it is essential to include relevant literature and previous research findings in these sections. 2. Undefined contributions: The paper fails to clearly outline its unique contributions. It is important to explicitly state the novel aspects or findings of this research. Additionally, thorough proofreading is recommended to enhance the clarity and professionalism of the manuscript. 3. Comparison with previous works is missing: The paper does not adequately compare its findings with existing literature in the field. Including such a comparison is crucial for situating the research within the current scholarly discourse and demonstrating its relevance and originality. 4. Experimental setup and parameters not specified: The paper does not provide details about the experimental setup, including the values of the parameters used. This information is vital for replicability and for readers to understand the context and limitations of the experiments conducted. 5. Lack of results on transaction inclusion times: The results concerning transaction inclusion times are not presented. Including this data is important for a comprehensive understanding of how PBS impacts the Ethereum blockchain, especially in terms of efficiency and performance. ### Reasons to not accept the paper 1. This paper needs improvement in its written presentation. Specifically, the writing is incomplete in section Contributions on page 1, the references are insufficient and not formal, and the equations and statements require further clarifications for better understanding. 2. This paper does not adhere to the USENIX formatting standards. 3. The theoretical model oversimplifies complex blockchain dynamics. 4. The simulations and results presented in this paper are inadequate. They require further development and expansion to comprehensively address the research questions. This includes conducting additional simulations to provide a more robust dataset, as well as a more detailed analysis of the results to draw meaningful conclusions. The parameters used in the simulation are missing for readers to replicate the results. TO-DO USENIX REVIEW =========================================================================== - [x] Add game theoretical framwork - [x] Add contribution bullet point (introduction) - [x] Provide a more detailed explaination in formulas and terminologies (definitions) - [x] Provide more simulation results (result) - [x] Add advantages of using ABM in this case (methodology) - [x] Add reference in the introduction and background section - [x] Add comparison to previous work (related work) - [ ] Define experiment setup and paremeters (methodology)