Blockchain in the Lens of BFT

Dahlia Malkhi, VMware Research

Abstract: 

Blockchain is a Byzantine Fault Tolerant (BFT) replicated state machine, in which each state-update is by itself a Turing machine with bounded resources. The core algorithm for achieving BFT in a Blockchain appears completely different from classical BFT algorithms:

  • Classical solutions like DLS, PBFT solve BFT among a small-to-medium group of known participants. Such algorithms consist of multiple rounds of message exchanges carrying votes and safety-proofs. They are evidently quite intimidating to the non-expert.
  • In contrast, Bitcoin solves BFT among a very large group of unknown users. In each time-period, one user broadcasts a single message carrying a Proof-of-Work (PoW). No other messages or information is exchanged.

What a difference between the two worlds!

Recent advances in blockchain technology blur these boundaries. Namely, hybrid solutions such as Byzcoin, Bitcoin-NG, Hybrid Consensus, Casper and Solida, anchor off-chain BFT decisions inside a PoW chain or the other way around. Moreover, innovative solutions in the age of blockchains, such as Honeybadger, ALGORAND, Tendermint, SBFT, and Hot-Stuff, revisit the BFT setting with greater scalability and simplicity.

Confused? Come hear this keynote in which we describe Blockchain in the lens of BFT and BFT in the lens of Blockchain, and provide common algorithmic foundations for both.

Dahlia Malkhi, VMware Research

Dahlia is an applied and foundational researcher, since the early nineties, in broad aspects of reliability and security in distributed systems.

In 2014, after the closing of the Microsoft Research Silicon Valley lab, Dahlia co-founded VMware Research and became a Principal Researcher at VMware. From 2004-2014, she was a principal researcher at Microsoft Research, Silicon Valley. From 1999-2007, she was a tenured associate professor at the Hebrew University of Jerusalem. In 2004, Dahlia actually left for a brief sabbatical at Microsoft Research, but was bitten by the Silicon Valley bug and stayed there. Dahlia holds a Ph.D., an M.Sc. and a B.Sc. in computer science from the Hebrew University of Jerusalem.

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BibTeX
@conference {216686,
author = {Dahlia Malkhi},
title = {Blockchain in the Lens of {BFT}},
year = {2018},
address = {Boston, MA},
publisher = {{USENIX} Association},
month = jul,
}

Presentation Audio