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Ph.D. Defense: Saad Quader

October 23, 2020 @ 3:30 pm - 5:30 pm EDT

Title: Security of Proof-of-Stake Blockchains

Ph.D. Candidate: Saad Quader

Major Advisor: Prof. Alexander Russell 

Associate Advisors: Prof. Benjamin Fuller and Prof. Walter Krawec

Date/Time:  Friday, October 23rd, 2020, 3:30 pm – 5:30 pm

Webex Meeting Link: https://uconn-cmr.webex.com/uconn-cmr/j.php?MTID=mc2fc14fe991eb93722e73358d4134712

Meeting Number: 120 029 4507

Password: P2r6d54m5eJ

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+1-415-655-0002 US Toll
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In the past decade, blockchain technology has emerged as a foundation for a diverse range of distributed applications, notably cryptocurrencies and decentralized ledger. These protocols allow the users — across the globe and not needing to trust one another — exchange messages and eventually reach an agreement.

Currently, the most popular blockchain technology is the Proof-of-Work (PoW) paradigm, popularized by the cryptocurrency Bitcoin. Alternative paradigms, such as Proof-of-Stake (PoS), aim to provide the same functionalities and security as PoW while requiring only a fraction of a PoW network’s enormous energy cost. This, however, is non-trivial.

In this dissertation, we study the security of PoS blockchains in the eventual consensus model under the so-called “longest-chain rule.” 

  • First, we show that PoS blockchains have the same asymptotic security guarantee as those of the PoW blockchains (published at ACM SODA 2020). 
  • Next, we generalize this analysis and show that we can securely use a broader class of protocols for electing “leaders” — users who can create new blocks — at each round (accepted at IEEE ICDCS 2020). 
  • Finally, we analyze the security of the “randomness beacon” within two important PoS blockchain protocols: Ouroboros Praos and Snow White. Our results demarcate the parameter settings for which these protocols remain secure.

Our results have already made an impact in the industry, in that a leading PoS cryptocurrency Cardano is using our results and recommendations for designing their protocol.

About the Talk: In my talk, I will focus on our recent ICDCS 2020 paper. My goal will be to

  • Tell you what “consistency” means for blockchains
  • Motivate the question “how fast do we achieve consistency?”
  • Tell you about the insights we gained from our work
  • Give you intuitions behind our analysis


October 23, 2020
3:30 pm - 5:30 pm EDT

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