Security for proof of work blockchains via checkpointing
Pan, Siheng
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PAN-THESIS-2021.pdf
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https://hdl.handle.net/2142/113237
Description
Title
Security for proof of work blockchains via checkpointing
Author(s)
Pan, Siheng
Issue Date
2021-07-21
Director of Research (if dissertation) or Advisor (if thesis)
Viswanath, Pramod
Department of Study
Electrical & Computer Eng
Discipline
Electrical & Computer Engr
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Date of Ingest
2022-01-12T22:51:33Z
Keyword(s)
Blockchain
Checkpointing
Prism
Abstract
Finality gadgets are comprised of a Byzantine Fault Tolerant (BFT) protocol finalizing blocks produced by a Proof-of-Work (PoW) or Proof-of-Stake (PoS) chain protocol. They have become very popular methods for combining the best features of the BFT and PoW protocols and are proposed for deployment in many major blockchains. While the finality gadget architecture has been explored through many distinct dimensions, their performance under an adversarial majority in the PoW chain protocol has received scant attention. The raison d’etre for a finality gadget is to provide safety even under an adversarial majority in the PoW chain (hence the term “finality” gadget). While safety guarantee is easily provided by the finality gadget, significant liveness vulnerabilities exist. The proposed remedy achieves asymptotic liveness but the achieved chain quality (the fraction of honest blocks in the ledger) and latency deteriorate exponentially as the adversary power increases beyond 50%. Furthermore, the proposed gadget does not guarantee liveness in protocols beyond the Nakamoto longest chain.
In this thesis, we propose Advocate, a new finality gadget architecture, which achieves two main results: (a) optimal chain quality and low latency under a super-majority adversary for the Nakamoto longest chain protocol and (b) generalization to a variety of parallel-chain based scaling architectures, including OHIE, Prism and ledger combiner. We demonstrate via a full-stack implementation the robustness of Advocate under a 90% adversarial majority.
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PAN-THESIS-2021.pdf
