JY
Jiangshan Yu
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Byzantine Fault Tolerance (BFT) Consensus protocols with trusted hardware assistance have been extensively explored for their improved resilience to tolerate more faulty processes. Nonetheless, the potential of trust hardware has been scarcely investigated in leaderless BFT protocols. RedBelly is assumed to be the first blockchain network whose consensus is based on a truly leaderless BFT algorithm. This paper proposes a trusted hardware-assisted leaderless BFT consensus protocol by offering a hybrid solution for the set BFT problem defined in the RedBelly blockchain. Drawing on previous studies, we present two crucial trusted services: the counter and the collector. Based on these two services, we introduce two primitives to formulate our leaderless BFT protocol: a hybrid verified broadcast (VRB) protocol and a hybrid binary agreement. The hybrid VRB protocol enhances the hybrid reliable broadcast protocol by integrating a verification function. This addition ensures that a broadcast message is verified not only for authentication but also for the correctness of its content. Our hybrid BFT consensus is integrated with these broadcast protocols to deliver binary decisions on all proposals. We prove the correctness of the proposed hybrid protocol and demonstrate its enhanced performance in comparison to the prior trusted BFT protocol.
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Byzantine Fault Tolerance (BFT) Consensus protocols with trusted hardware assistance have been extensively explored for their improved resilience to tolerate more faulty processes. Nonetheless, the potential of trust hardware has been scarcely investigated in leaderless BFT protocols. RedBelly is assumed to be the first blockchain network whose consensus is based on a truly leaderless BFT algorithm. This paper proposes a trusted hardware-assisted leaderless BFT consensus protocol by offering a hybrid solution for the set BFT problem defined in the RedBelly blockchain. Drawing on previous studies, we present two crucial trusted services: the counter and the collector. Based on these two services, we introduce two primitives to formulate our leaderless BFT protocol: a hybrid verified broadcast (VRB) protocol and a hybrid binary agreement. The hybrid VRB protocol enhances the hybrid reliable broadcast protocol by integrating a verification function. This addition ensures that a broadcast message is verified not only for authentication but also for the correctness of its content. Our hybrid BFT consensus is integrated with these broadcast protocols to deliver binary decisions on all proposals. We prove the correctness of the proposed hybrid protocol and demonstrate its enhanced performance in comparison to the prior trusted BFT protocol.
We describe and analyze perishing mining, a novel blockwithholding mining strategy that lures profit-driven miners away from doing useful work on the public chain by releasing block headers from a privately maintained chain. We then introduce the dual private chain (DPC) attack, where an adversary that aims at double spending increases its success rate by intermittently dedicating part of its hash power to perishing mining. We detail the DPC attack's Markov decision process, evaluate its double spending success rate using Monte Carlo simulations. We show that the DPC attack lowers Bitcoin's security bound in the presence of profit-driven miners that do not wait to validate the transactions of a block before mining on it.
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We describe and analyze perishing mining, a novel blockwithholding mining strategy that lures profit-driven miners away from doing useful work on the public chain by releasing block headers from a privately maintained chain. We then introduce the dual private chain (DPC) attack, where an adversary that aims at double spending increases its success rate by intermittently dedicating part of its hash power to perishing mining. We detail the DPC attack's Markov decision process, evaluate its double spending success rate using Monte Carlo simulations. We show that the DPC attack lowers Bitcoin's security bound in the presence of profit-driven miners that do not wait to validate the transactions of a block before mining on it.
DAMYSUS
Streamlined BFT Consensus Leveraging Trusted Components
Recently, streamlined Byzantine Fault Tolerant (BFT) consensus protocols, such as HotStuff, have been proposed as a means to circumvent the inefficient view-changes of traditional BFT protocols, such as PBFT. Several works have detailed trusted components, and BFT protocols that leverage them to tolerate a minority of faulty nodes and use a reduced number of communication rounds. Inspired by these works we identify two basic trusted services, respectively called the Checker and Accumulator services, which can be leveraged by streamlined protocols. Based on these services, we design Damysus, a streamlined protocol that improves upon HotStuff's resilience and uses less communication rounds. In addition, we show how the Checker and Accumulator services can be adapted to develop Chained-Damysus, a chained version of Damysus where operations are pipelined for efficiency. We prove the correctness of Damysus and Chained-Damysus, and evaluate their performance showcasing their superiority compared to previous protocols.
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Recently, streamlined Byzantine Fault Tolerant (BFT) consensus protocols, such as HotStuff, have been proposed as a means to circumvent the inefficient view-changes of traditional BFT protocols, such as PBFT. Several works have detailed trusted components, and BFT protocols that leverage them to tolerate a minority of faulty nodes and use a reduced number of communication rounds. Inspired by these works we identify two basic trusted services, respectively called the Checker and Accumulator services, which can be leveraged by streamlined protocols. Based on these services, we design Damysus, a streamlined protocol that improves upon HotStuff's resilience and uses less communication rounds. In addition, we show how the Checker and Accumulator services can be adapted to develop Chained-Damysus, a chained version of Damysus where operations are pipelined for efficiency. We prove the correctness of Damysus and Chained-Damysus, and evaluate their performance showcasing their superiority compared to previous protocols.
While previous works have discussed the network delay upper bound that guarantees the consistency of Nakamoto consensus, measuring the actual network latencies and evaluating their impact on miners/pools in Bitcoin remain open questions. This paper fills this gap by: (1) defining metrics that quantify the impact of network latency on the mining network; (2) developing a tool, named miner entanglement (ME), to experimentally evaluate these metrics with a focus on the network latency of the top mining pools; and (3) quantifying the impact of the current network delays on Bitcoin’s mining network. For example, we evaluated that Poolin, a Bitcoin mining pool, was able to gain between 0.5% and 1.9% of blocks in addition (i.e., from 36.27 BTC to 137.83 BTC) per week thanks to its low network latency. Moreover, as pools are rational in Bitcoin, we model the strategy a pool would follow to improve its network latency (e.g., by leveraging our ME tool) as a two party game. We show that a Bitcoin mining pool could improve its effective hash rate by up to 4.5%. For a multi-party game, we use a state-of-the-art Bitcoin mining simulator to study the situation where all pools attempt to improve their network latency and show that the largest mining pools would improve their revenue and reach a Nash equilibrium while the smaller mining pools would suffer from a decreased access to the network, and therefore a decreased revenue. These conclusions further incentivize the centralisation of the mining network in Bitcoin, and provide an empirical explanation for the observed tendency of pools to design and rely on low latency private networks.
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While previous works have discussed the network delay upper bound that guarantees the consistency of Nakamoto consensus, measuring the actual network latencies and evaluating their impact on miners/pools in Bitcoin remain open questions. This paper fills this gap by: (1) defining metrics that quantify the impact of network latency on the mining network; (2) developing a tool, named miner entanglement (ME), to experimentally evaluate these metrics with a focus on the network latency of the top mining pools; and (3) quantifying the impact of the current network delays on Bitcoin’s mining network. For example, we evaluated that Poolin, a Bitcoin mining pool, was able to gain between 0.5% and 1.9% of blocks in addition (i.e., from 36.27 BTC to 137.83 BTC) per week thanks to its low network latency. Moreover, as pools are rational in Bitcoin, we model the strategy a pool would follow to improve its network latency (e.g., by leveraging our ME tool) as a two party game. We show that a Bitcoin mining pool could improve its effective hash rate by up to 4.5%. For a multi-party game, we use a state-of-the-art Bitcoin mining simulator to study the situation where all pools attempt to improve their network latency and show that the largest mining pools would improve their revenue and reach a Nash equilibrium while the smaller mining pools would suffer from a decreased access to the network, and therefore a decreased revenue. These conclusions further incentivize the centralisation of the mining network in Bitcoin, and provide an empirical explanation for the observed tendency of pools to design and rely on low latency private networks.