Vincent Gramoli

School of Computer Science
1, Cleveland St.,
NSW 2006 Sydney
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Blog - Thinking Distributed

Latest Posts

Smart Redbelly: A Retrospective

As the Smart Redbelly Blockchain has just been accepted for publcation in the flagship journal of Computer Science, IEEE TC [1], now is the right time to look back at what makes Redbelly Blockchain unique. The original idea of Redbelly Blockchain was to make blockchain secure and efficient. We achieve efficiency by introducing collaboration: Instead of letting participants compete to insert the next block, our collaborative approach leveraged their resources to scale. Although seemingly simple, this idea took lawyers 6 years to recognise its novelty and we are happy that the US Patent and Trademark Office has finally approved our corresponding patent.
The Fault Tolerant Blockchain

Blockchain promises to prevent global crashes like the CrowdStrike outage that affected 8.5 millions of computers around the world. Intuitively, this is due to the decentralisation of the blockchain software and the diversity of nodes participating in the blockchain network. Interestingly, the first thorough investigation of the blockchain tolerance to failures [1] has just revealed surprising results depending on the considered blockchain protocol: While Redbelly could tolerate failures, Avalanche and Solana could not.
Blockchain Has Become Collaborative

With the new release of Redbelly Network, blockchain has entered a new era: collaboration. Since its inception, the blockchain protocol has always been built on competition: as only one of the validator nodes could win the lottery by imposing its block to the rest of the system. This competition led to adversarial effects over time. With the number of validators entering the competition increasing, due to the built-in incentives, so did the amount of wasted resources. As a result, performance would never increase with more validators.
How To Avoid Generalised Outages

The dependence of critical industry sectors on any specific technology is dangerous. It translates into assuming that health services, distribution of goods, transportation can serve us as long as a single product, like Microsoft Windows, does not experience a bug. This is giving way too much trust to any central vendor, let alone a single product.
Attack Resilience While Ordering Transactions

Front running attacks that are illegal on Wall St. happen all the time on Main St. due to the lack of regulation around the blockchain technology. The difficulty, as mentioned in a previous blog post, is that preventing the reordering of transactions is costly and consists of building transaction dependency graphs that may create cylic dependencies. We have thus published two scientific articles to address these two problems [1,2].
Blockchain Complies With Regulation

As CZ, the former Binance CEO, is entering jail for having violated anti money laundering laws in the US through the use of blockchain technology, the solution to compliant blockchain has just appeared. For the last 15 years, blockchain has been a refuge for pseudonymous or anonymous users to trade assets without trusting a central financial institution. As regulation is catching up with technology, Redbelly Network has just launched its new open network simply requiring its users to first register with an identity provider.
Optimal Prevention Of Reordering Attacks

Although illegal on Wall Street, reordering attacks happen regularly on blockchains. With researchers from the University of Sydney, we recently solved this problem optimally even for networks where message delays are arbitrary [1]. The key idea is to combine threshold signatures with information dissemination to achieve optimal communication complexity. The scientific article will be published in the proceedings of the 54th IEEE/IFIP International Conference on Dependable Systems and Networks (DSN) in Brisbane, Australia in June 2024.
Blockchain Can Finally Tolerate Colluding Majority

We found a blockchain protocol, called ZLB [1], to cope with a coalition of any size. Before that, adversaries controlling the majority of the resources could break any blockchain network. This has been dramatic, as we are aware of many millions of dollars that got lost or stolen due to this problem. The key to bypass this limitation relies on solving the accountable consensus problem: either reaching consensus because the coalition does not lie sufficiently to other nodes, or producing undeniable proofs of fraud to ban liars from executing further consensus instances. The amount of applications of ZLB is vast and its performance is close to the best performing blockchains. Update: this scientific publication [1] has just received a Best Paper Award from the 54th Annual IEEE/IFIP International Conference on Dependable Systems and Networks.
Debunking Blockchain Consensus Myths

Blockchain technologies rely on a large body of complex research topics like the Byzantine consensus problem. Although such a problem was defined four decades ago, its subtle ramifications are largely misunderstood by many blockchain developers, let alone application programmers who build upon these blockchains. These misconceptions are dramatic as they prevent these applications from working efficiently and they make them vulnerable to attacks. In a recent chapter [1], we debunk the 10 major myths about blockchain consensus by evaluating three distributed ledgers, Hyperledger Fabric, Redbelly Blockchain and R3 Corda, as well as three important consensus algorithms, BFT-SMaRt, Democratic BFT and HotStuff. Below we discuss the five first myths.
Cross Chain Payments Made Possible

For blockchain to become securely interoperable, one must first solve the cross-chain payment problem. Not only should one user of a blockchain be able to pay the user of another blockchain successfully, but it should do so without assuming that messages always take less than some period to arrive. Otherwise the solution can be easily hacked. It turns out that the general problem is unsolvable but, fortunately, there exists a solution to a variant of this problem.
Why Blockchains Were Actually Centralised

Most blockchains have an inherently centralised design, which restricts their scalability. It is the consequence of research on the consensus problem from the 80s and the influential leader-based consensus protocols from the 2000s. We had to wait until until 2021 for the problem to be redefined in a decentralised way for blockchains to scale to large networks.
Fair Resource Sharing Using Crypto

With the digital revolution, services are becoming decentralised. This trend is driven by users wanting to retain the custody of their personal identifiable information or data, the growing use of Web3 over the Internet, and the desire for nations to become self-sovereign in a globalised world. In this decentralised setting, tech-savvy participants regularly front-run others to get an unfair access to resources before their victims. This unfair access impacts financial resources every day but could soon generalize to resources that are vital to a nation’s economy (e.g., energy). Here we discuss the problem and list recent cryptographic solutions to ensure a fair access to resources.
Formal Verif To The Rescue

As a new flaw in the Solana consensus protocol will be presented in four days [1], it might be the right time to discuss the importance of formal methods. Update: 2 days later my colleagues from Bern also demonstrated that Avalanche consensus cannot provide a decent trade-off between security and performance [6]. Classic blockchains had a hard time being adopted in production. When the largest bank of Australia asked me to do some consulting work, I had to inform them that the way they were using Ethereum was flawed as we managed to hack a copy of their setup [2]. After we reported the vulnerability to both Geth and Parity security teams, they both acknowledged the problem but it took some time for Parity to implement our counter measure. It is thus not surprising that the traditional finance industry has been slow at integrating blockchain to their production system. We discuss the importance of the problem and how we tackled it with formal verification.
Why Non Dictatorship Is Vital For Blockchain Governance

Non-dictatorship is a property that appeared in the work of Arrow back in 1950 [1]. We explain why it turns out to be a fundamental property of blockchain governance. We then explain how one can devise a governance protocol that ensures this property and refer to its smart contract implementation.

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