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Ouroboros Praos: An Adaptively-Secure, Semi-synchronous Proof-of-Stake Blockchain

2018; Springer Science+Business Media; Linguagem: Inglês

10.1007/978-3-319-78375-8_3

1611-3349

Bernardo David, Peter Gaži, Aggelos Kiayias, Alexander Russell,

Distributed systems and fault tolerance

We present “Ouroboros Praos”, a proof-of-stake blockchain protocol that, for the first time, provides security against fully-adaptive corruption in the semi-synchronous setting: Specifically, the adversary can corrupt any participant of a dynamically evolving population of stakeholders at any moment as long the stakeholder distribution maintains an honest majority of stake; furthermore, the protocol tolerates an adversarially-controlled message delivery delay unknown to protocol participants. To achieve these guarantees we formalize and realize in the universal composition setting a suitable form of forward secure digital signatures and a new type of verifiable random function that maintains unpredictability under malicious key generation. Our security proof develops a general combinatorial framework for the analysis of semi-synchronous blockchains that may be of independent interest. We prove our protocol secure under standard cryptographic assumptions in the random oracle model.