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arXiv · 1910.02218

Proof-of-Stake Longest Chain Protocols: Security vs Predictability

Vivek Bagaria·Amir Dembo·Sreeram Kannan·Sewoong Oh·David Tse·Pramod Viswanath·Xuechao Wang·Ofer Zeitouni
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Abstract

The Nakamoto longest chain protocol is remarkably simple and has been proven to provide security against any adversary with less than 50% of the total hashing power. Proof-of-stake (PoS) protocols are an energy efficient alternative; however existing protocols adopting Nakamoto's longest chain design achieve provable security only by allowing long-term predictability (which have serious security implications). In this paper, we prove that a natural longest chain PoS protocol with similar predictability as Nakamoto's PoW protocol can achieve security against any adversary with less than 1/(1+e) fraction of the total stake. Moreover we propose a new family of longest chain PoS protocols that achieve security against a 50% adversary, while only requiring short-term predictability. Our proofs present a new approach to analyzing the formal security of blockchains, based on a notion of adversary-proof convergence.

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Vivek Bagaria, Amir Dembo, Sreeram Kannan, Sewoong Oh, David Tse, Pramod Viswanath, Xuechao Wang, Ofer Zeitouni. 2019-10-05. Proof-of-Stake Longest Chain Protocols: Security vs Predictability. https://arxiv.org/abs/1910.02218

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