In the area of blockchain research proof of stake has long posed many questions for cryptographers and the subject has been of primary importance for IOHK researchers over the past two years. Professor Aggelos Kiayias, Chief Scientist at IOHK, has led work with a team of cryptographers to formalise a family of protocols called Ouroboros. It is a great distinction for their efforts that their paper describing the protocol was accepted to Crypto 2017, the foremost cryptographic event, and another paper was heard this month at sister event Eurocrypt.
Eurocrypt is the flagship European conference of the main international community of cryptographers, the International Association for Cryptologic Research. About 370 delegates from countries worldwide arrived in Tel Aviv, Israel, to hear cutting edge research being presented from across the spectrum of cryptography. In all, there were about 70 presentations across four days.
This year, blockchain was more prominent than it had ever been at Eurocrypt. There were four papers presented during a dedicated blockchain morning session on the second day. The following day there was a talk on the 30-year history of cryptocurrencies, given by Matthew Green, a cryptographer at Johns Hopkins Information Security Institute. Three best papers were selected for an award at Eurocrypt, and one of them was on blockchain, Simple Proofs of Sequential Work by Bram Cohen and Krzysztof Pietrzak.
Academic interest in the area has nowhere near matched the rapid proliferation of blockchain projects during the past few years, and the increased focus of cryptographers at events like Eurocrypt brings a welcome professionalisation to the industry.
To be heard at the conference, papers must be submitted for consideration in a process called peer review. This notoriously tough sifting process can typically involve three or four people reviewing the paper, and it passing a programme committee of three dozen or more people, to ensure it makes a novel contribution to the scientific literature that advances computer science. Most papers are rejected. A double-blind admission procedure where both authors and reviewers are anonymous adds objectivity.
The novel feature of Ouroboros Praos is that it is the first proof-of-stake blockchain to be able to scale for widespread use and provide security against adaptive attackers. These are attackers that can instantly corrupt protocol participants, and the only restriction is that only a minority of the total stake can be in corrupted hands. A Distributed Denial of Service (DDoS) attack is a real-world example of such an instant attack.
Ouroboros Praos offers the same security guarantees as Bitcoin in that it can withstand attacks from stronger adversaries in harsh network conditions, such as where an attacker has some control over network delays affecting messages sent by all participants.
No other proof-of-stake protocol that has been peer reviewed at this level can provably offer this level of security guarantee under these conditions.
Peter Gaži, who presented: “Eurocrypt is one of the premier venues for presenting cryptoglogic research and it’s an honour for us to present our work here. The fact that we were invited serves as evidence the broader academic community is showing more interest in this topic.”
Aside from Peter and Aggelos, the other researchers on the Ouroboros team are Bernardo David, Alexander Russell, Roman Oliynykov, Christian Badertscher, and Vassilis Zikas. The previous Ouroboros paper, first in this line of research, is the first proof-of-stake protocol to be provably secure and peer reviewed at a leading cryptographic event. Ouroboros has a real-world implementation in Cardano, the top 10 cryptocurrency built by IOHK.
Artwork: David Clode