TY - GEN

T1 - Proof-of-Stake Mining Games with Perfect Randomness

AU - Ferreira, Matheus V.X.

AU - Weinberg, S. Matthew

N1 - Funding Information:
∗Supported by NSF CAREER Award CCF-1942497.
Publisher Copyright:
© 2021 ACM.

PY - 2021/7/18

Y1 - 2021/7/18

N2 - Proof-of-Stake blockchains based on a longest-chain consensus protocol are an attractive energy-friendly alternative to the Proof-of-Work paradigm. However, formal barriers to getting the incentives right were recently discovered, driven by the desire to use the blockchain itself as a source of pseudorandomness [4]. We consider instead a longest-chain Proof-of-Stake protocol with perfect, trusted, external randomness (e.g. a randomness beacon). We produce two main results. First, we show that a strategic miner can strictly outperform an honest miner with just 32.8% of the total stake. Note that a miner of this size cannot outperform an honest miner in the Proof-of-Work model [21]. This establishes that even with access to a perfect randomness beacon, incentives in Proof-of-Work and Proof-of-Stake longest-chain protocols are fundamentally different. Second, we prove that a strategic miner cannot outperform an honest miner with 30.8% of the total stake. This means that, while not quite as secure as the Proof-of-Work regime, desirable incentive properties ofProof-of-Work longest-chain protocols can be approximately recovered via Proof-of-Stake with a perfect randomness beacon. The space of possible strategies in a Proof-of-Stake mining game is significantly richer than in a Proofof- Work game. Our main technical contribution is a characterization of potentially optimal strategies for a strategic miner, and in particular a proof that the corresponding infinite-state MDP admits an optimal strategy that is positive recurrent.

AB - Proof-of-Stake blockchains based on a longest-chain consensus protocol are an attractive energy-friendly alternative to the Proof-of-Work paradigm. However, formal barriers to getting the incentives right were recently discovered, driven by the desire to use the blockchain itself as a source of pseudorandomness [4]. We consider instead a longest-chain Proof-of-Stake protocol with perfect, trusted, external randomness (e.g. a randomness beacon). We produce two main results. First, we show that a strategic miner can strictly outperform an honest miner with just 32.8% of the total stake. Note that a miner of this size cannot outperform an honest miner in the Proof-of-Work model [21]. This establishes that even with access to a perfect randomness beacon, incentives in Proof-of-Work and Proof-of-Stake longest-chain protocols are fundamentally different. Second, we prove that a strategic miner cannot outperform an honest miner with 30.8% of the total stake. This means that, while not quite as secure as the Proof-of-Work regime, desirable incentive properties ofProof-of-Work longest-chain protocols can be approximately recovered via Proof-of-Stake with a perfect randomness beacon. The space of possible strategies in a Proof-of-Stake mining game is significantly richer than in a Proofof- Work game. Our main technical contribution is a characterization of potentially optimal strategies for a strategic miner, and in particular a proof that the corresponding infinite-state MDP admits an optimal strategy that is positive recurrent.

KW - cryptocurrency

KW - energy-efficiency

KW - Nash equilibrium

KW - proof-of-stake blockchains

KW - random beacons

UR - http://www.scopus.com/inward/record.url?scp=85111954035&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85111954035&partnerID=8YFLogxK

U2 - 10.1145/3465456.3467636

DO - 10.1145/3465456.3467636

M3 - Conference contribution

AN - SCOPUS:85111954035

T3 - EC 2021 - Proceedings of the 22nd ACM Conference on Economics and Computation

SP - 433

EP - 453

BT - EC 2021 - Proceedings of the 22nd ACM Conference on Economics and Computation

PB - Association for Computing Machinery, Inc

T2 - 22nd ACM Conference on Economics and Computation, EC 2021

Y2 - 18 July 2021 through 23 July 2021

ER -