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

Bernardo David, Peter Gazi, Aggelos Kiayias, Alexander Russell

Research output: Chapter in Book/Report/Conference proceedingConference contribution


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.
Original languageEnglish
Title of host publicationAdvances in Cryptology - EUROCRYPT 2018
Number of pages33
ISBN (Electronic)978-3-319-78375-8
ISBN (Print)978-3-319-78374-1
Publication statusPublished - 31 Mar 2018
EventEUROCRYPT 2018 - Tel Aviv, Israel
Duration: 29 Apr 20183 May 2018

Publication series

NameLecture Notes in Computer Science (LNCS)
PublisherSpringer, Cham
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


ConferenceEUROCRYPT 2018
Abbreviated titleEUROCRYPT 2018
CityTel Aviv
Internet address


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