Ordered Consensus with Equal Opportunity

Fuente: arXiv
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Autori principali: Zhang, Yunhao, Ni, Haobin, Basu, Soumya, Cohen, Shir, Yin, Maofan, Alvisi, Lorenzo, van Renesse, Robbert, Chen, Qi, Zhou, Lidong
Natura: Preprint
Pubblicazione: 2025
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author Zhang, Yunhao
Ni, Haobin
Basu, Soumya
Cohen, Shir
Yin, Maofan
Alvisi, Lorenzo
van Renesse, Robbert
Chen, Qi
Zhou, Lidong
author_facet Zhang, Yunhao
Ni, Haobin
Basu, Soumya
Cohen, Shir
Yin, Maofan
Alvisi, Lorenzo
van Renesse, Robbert
Chen, Qi
Zhou, Lidong
contents The specification of state machine replication (SMR) has no requirement on the final total order of commands. In blockchains based on SMR, however, order matters, since different orders could provide their clients with different financial rewards. Ordered consensus augments the specification of SMR to include specific guarantees on such order, with a focus on limiting the influence of Byzantine nodes. Real-world ordering manipulations, however, can and do happen even without Byzantine replicas, typically because of factors, such as faster networks or closer proximity to the blockchain infrastructure, that give some clients an unfair advantage. To address this challenge, this paper proceeds to extend ordered consensus by requiring it to also support equal opportunity, a concrete notion of fairness, widely adopted in social sciences. Informally, equal opportunity requires that two candidates who, according to a set of criteria deemed to be relevant, are equally qualified for a position (in our case, a specific slot in the SMR total order), should have an equal chance of landing it. We show how randomness can be leveraged to keep bias in check, and, to this end, introduce the secret random oracle (SRO), a system component that generates randomness in a fault-tolerant manner. We describe two SRO designs based, respectively, on trusted hardware and threshold verifiable random functions, and instantiate them in Bercow, a new ordered consensus protocol that, by approximating equal opportunity up to within a configurable factor, can effectively mitigate well-known ordering attacks in SMR-based blockchains.
format Preprint
id arxiv_https___arxiv_org_abs_2509_09868
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Ordered Consensus with Equal Opportunity
Zhang, Yunhao
Ni, Haobin
Basu, Soumya
Cohen, Shir
Yin, Maofan
Alvisi, Lorenzo
van Renesse, Robbert
Chen, Qi
Zhou, Lidong
Distributed, Parallel, and Cluster Computing
Cryptography and Security
Multiagent Systems
The specification of state machine replication (SMR) has no requirement on the final total order of commands. In blockchains based on SMR, however, order matters, since different orders could provide their clients with different financial rewards. Ordered consensus augments the specification of SMR to include specific guarantees on such order, with a focus on limiting the influence of Byzantine nodes. Real-world ordering manipulations, however, can and do happen even without Byzantine replicas, typically because of factors, such as faster networks or closer proximity to the blockchain infrastructure, that give some clients an unfair advantage. To address this challenge, this paper proceeds to extend ordered consensus by requiring it to also support equal opportunity, a concrete notion of fairness, widely adopted in social sciences. Informally, equal opportunity requires that two candidates who, according to a set of criteria deemed to be relevant, are equally qualified for a position (in our case, a specific slot in the SMR total order), should have an equal chance of landing it. We show how randomness can be leveraged to keep bias in check, and, to this end, introduce the secret random oracle (SRO), a system component that generates randomness in a fault-tolerant manner. We describe two SRO designs based, respectively, on trusted hardware and threshold verifiable random functions, and instantiate them in Bercow, a new ordered consensus protocol that, by approximating equal opportunity up to within a configurable factor, can effectively mitigate well-known ordering attacks in SMR-based blockchains.
title Ordered Consensus with Equal Opportunity
topic Distributed, Parallel, and Cluster Computing
Cryptography and Security
Multiagent Systems
url https://arxiv.org/abs/2509.09868