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Snow White: Robustly Reconfigurable Consensus and Applications to Provably Secure Proof of Stake

  • Phil Daian
  • Rafael Pass
  • Elaine ShiEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11598)

Abstract

We present the a provably secure proof-of-stake protocol called Snow White. The primary application of Snow White is to be used as a “green” consensus alternative for a decentralized cryptocurrency system with open enrollement. We break down the task of designing Snow White into the following core challenges:
  1. 1.

    identify a core “permissioned” consensus protocol suitable for proof-of-stake; specifically the core consensus protocol should offer robustness in an Internet-scale, heterogeneous deployment;

     
  2. 2.

    propose a robust committee re-election mechanism such that as stake switches hands in the cryptocurrency system, the consensus committee can evolve in a timely manner and always reflect the most recent stake distribution; and

     
  3. 3.

    relying on the formal security of the underlying consensus protocol, prove the full end-to-end protocol to be secure—more specifically, we show that any consensus protocol satisfying the desired robustness properties can be used to construct proofs-of-stake consensus, as long as money does not switch hands too quickly.

     

Snow White was publicly released in September 2016. It provides the first formal, end-to-end proof of a proof-of-stake system in a truly decentralized, open-participation network, where nodes can join at any time (not necessarily at the creation of the system). We also give the first formal treatment of a well-known issue called “costless simulation” in our paper, proving both upper- and lower-bounds that characterize exactly what setup assumptions are needed to defend against costless simulation attacks. We refer the reader to our detailed chronological notes on a detailed comparison of Snow White and other prior and concurrent works, as well as how subsequent works (including Ethereum’s proof-of-stake design) have since extended and improved our ideas.

Notes

Acknowledgments

We gratefully acknowledge Siqiu Yao and Yuncong Hu for lending critical help in building the simulator. We thank Lorenzo Alvisi for suggesting the name Snow White. We also thank Rachit Agarwal, Kai-Min Chung, and Ittay Eyal for helpful and supportive discussions.

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Copyright information

© International Financial Cryptography Association 2019

Authors and Affiliations

  1. 1.Cornell/CornellTechNew YorkUSA

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