What is Hotstuff and why is it a big deal?

Too often the blockchain industry may seem like a game of compromises. We often see very public negotiations between what new technologies promise and what they can achieve, exciting visions of the future and the banal realities of progress.

Bitcoin is innovative, of course, but it is too slow and unwieldy to replace fiat currency. Ethereum contracts are truly decentralized, sure, but who wants to write in Solidity? Ripple solves an urgent problem of ledger efficiency, but it is not really decentralized, nor is EOS; nor is BAT. The list goes on. For practically any new technology in the DLT space, there are detractors who will claim that the innovations lead to a sacrifice of security, speed, or decentralization. However, researchers at our advisor Bryan Ford’s home institute, the EPFL, have recently developed a new consensus algorithm that stands up to even the harshest scrutiny.

Asynchronous Byzantine Fault Tolerance has become one of the most popular forms of achieving consensus in the distributed ledger technology space. Because it has such deep roots in cryptography, and for that reason garners respect among the worlds foremost blockchain scientists, protocols like practical Byzantine Fault Tolerance have been adopted widely by a variety of projects. However, as with all aspects of technical development, there exists a faction of the crypto community that takes issue with asynchronous BFT solutions to the problem of consensus.

Critics argue that protocols like practical Byzantine Fault Tolerance can be slow and expensive to run, as well as self-restricting, given the existence of an upper bound on network delay. And unfortunately, these are all valid concerns. While it may be difficult to hear from a business or marketing perspective, it is important for STEM-based industries, especially one as new as ours, to hear when our best is not good enough — because it encourages our technologists and scientists to advance the field. And with the consensus algorithm HotStuff, researchers Maofan Yin, Dahlia Malkhi, Michael K. Reiter, Ittai Abraham, and Guy Gueta have done just that.

HotStuff makes outstanding progress on BFT consensus, one of the most solid foundations of blockchain technology. “HotStuff: BFT Consensus in the Lens of Blockchain” as it is formally titled, improves upon the reservations that critics wage against BFT blockchains, and it does so without sacrificing some other aspect of the protocol. In a brief half-page of code, HotStuff dramatically edits out the former inefficiencies of asynchronous BFT protocols. In fact, HotStuff makes BFT more scalable by an order of magnitude, as the algorithm’s view-change complexity is made quadratically faster — a function of simply the number of nodes in the network, as opposed to a function of the number of nodes squared, as is the case in PBFT.

HotStuff does this by returning to the original designs of Byzantine Fault Tolerance. As mentioned above, BFT protocols have garnered such respect in the blockchain world because their cryptographic history runs so deep. However, any cryptographer will tell you that BFT blockchains have a very different feel from classical BFT consensus models. HotStuff reexamines the original BFT designs from the perspective of their modern utility to the blockchain industry, offering a new algorithm that newly imagine three concepts that unite the classical designs and the operational concerns of blockchains: Votes, Blocks, and Pacemakers.

These advancements you can investigate in more technical detail here:

https://arxiv.org/abs/1803.05069

https://blockchainschool.epfl.ch/wp-content/uploads/2019/02/sbws19-malkhi.pdf

https://dahliamalkhi.wordpress.com/2018/10/24/hotstuff-three-chain-rules/

https://dahliamalkhi.wordpress.com/2018/03/13/casper-in-the-lens-of-bft/

See for yourself the brevity of the code, the obvious elegance in speaking to both classical academic cryptography and today’s frenzied blockchain industry.

Cypherium will integrate the HotStuff algorithm into its public protocol. We have identified the significance of this achievement, and we are proud to be the only public mainnet bringing this advancement to the crypto world.