Validators in permissionless, large-scale blockchains, such as Ethereum, are typically payoff-maximizing, rational actors. Ethereum relies on in-protocol incentives, like rewards for correct and timely votes, to induce honest behavior and secure the blockchain. However, external incentives, such as the block proposer’s opportunity to capture maximal extractable value (MEV), may tempt validators to deviate from honest protocol participation.We show a series of commitment attacks on LMD GHOST, a core part of Ethereum’s consensus mechanism. We demonstrate how a single adversarial block proposer can orchestrate long-range chain reorganizations by manipulating Ethereum’s reward system for timely votes. These attacks disrupt the intended balance of power between proposers and voters: by leveraging credible threats, the adversarial proposer can coerce voters from previous slots into supporting blocks that conflict with the honest chain, enabling a chain reorganization.In response, we introduce a novel reward mechanism that restores the voters’ role as a check against proposer power. Our proposed mitigation is fairer and more decentralized – not only in the context of these attacks – but also practical for implementation in Ethereum.

In 1985, Dolev and Reischuk proved a fundamental communication lower bounds on protocols achieving fault tolerant synchronous broadcast and consensus: any deterministic protocol solving those tasks (even against omission faults) requires at least a quadratic number of messages to be sent by nonfaulty parties. In contrast, many blockchain systems achieve consensus with seemingly linear communication per instance against Byzantine faults. We explore this dissonance in three main ways. First, we extend the Dolev-Reischuk family of lower bounds and prove a new lower bound for Crusader Broadcast protocols. Our lower bound for crusader broadcast requires non-trivial extensions and a much stronger Byzantine adversary with the ability to simulate honest parties. Secondly, we extend our lower bounds to all-but-m Crusader Broadcast, in which up to m parties are allowed to output a different value. Finally, we discuss the ways in which these lower bounds relate to the security of blockchain systems. We show how Eclipse-style attacks in such systems can be viewed as specific instances of the attacks used in our lower bound for Crusader Broadcast. This connection suggests a more systematic way of analyzing and reasoning about Eclipse-style attacks through the lens of the Dolev-Reischuk family of attacks.

Scientific research, and particularly research in mathematics, is arguably one of the crowning achievements of our collective human intellect. Its creation increasingly requires collaboration between multiple researchers with different and sometimes complementary backgrounds. On the other hand, its verification requires a careful matching between the expertise of reviewers and authors. Unfortunately, errors do happen and sometimes are only corrected many years after they appear in print, if at all. Nevertheless, at least when it comes to mathematical research, computer-verified formal proofs are possible as a final arbiter of mathematical truth, however, they are hard to produce even for relatively simple statements. Hence, such approaches typically lack far behind the current research frontier. In our work we present a novel blockchain-based system to tackle such issues. We discuss how the use of a combination of existing technologies such as decentralized file storage, review systems, smart contracts, non-fungible tokens (NFTs) and proof assistants can speed up and improve the quality and collaboration of mathematical research. As a proof of concept, we also design a mechanism to incentivize collaborative work and credit sharing that encourages provers to share their partial progresses without delay. Simultaneously, our mechanism incentivizes expert reviewers to challenge publicized proofs with formal proofs enabling dispute resolution, if needed.

Participation in permissionless blockchains results in competition over system resources, which needs to be controlled with fees. Until recently, Ethereum's fee mechanism was implemented via a first-price auction that resulted in unpredictable fees as well as other inefficiencies. Launched on August 5, 2021, EIP-1559 is an improved proposal that introduces a number of innovative features such as a dynamically adaptive basefee that is burnt, instead of being paid to the miners. Despite intense interest in understanding its properties, several basic questions such as whether and under what conditions does this protocol self-stabilize have remained elusive thus far.

Price of anarchy quantifies the degradation of social welfare in games due to the lack of a centralized authority that can enforce the optimal outcome. At its antipodes, mechanism design studies how to ameliorate these effects by incentivizing socially desirable behavior and implementing the optimal state as equilibrium. In practice, the responsiveness to such measures depends on the wealth of each individual. This leads to a natural, but largely unexplored, question. Does optimal mechanism design entrench, or maybe even exacerbate, social inequality? We study this question in nonatomic congestion games, arguably one of the most thoroughly studied settings from the perspectives of price of anarchy as well as mechanism design. We introduce a new model that incorporates the wealth distribution of the population and captures the income elasticity of travel time. This allows us to argue about the equality of wealth distribution both before and after employing a mechanism. We start our analysis by establishing a broad qualitative result, showing that tolls always increase inequality in symmetric congestion games under any reasonable metric of inequality, e.g., the Gini index. Next, we introduce the iniquity index, a novel measure for quantifying the magnitude of these forces towards a more unbalanced wealth distribution and show it has good normative properties (robustness to scaling of income, no-regret learning). We analyze iniquity both in theoretical settings (Pigou's network under various wealth distributions) as well as experimental ones (based on a large scale field experiment in Singapore). Finally, we provide an algorithm for computing optimal tolls for any point of the trade-off of relative importance of efficiency and equality. We conclude with a discussion of our findings in the context of theories of justice as developed in contemporary social sciences.