Asynchronous trustworthy transactions
Although Nakamoto’s original blockchain protocol has spurred significant innovation and financial interest in the last decade, its energy consumption  becomes problematic. Besides, transaction latencies are prohibitively high and the system sustains a very low throughput. We have witnessed hundreds of alternative solutions in the last decade. Each seeks to reduce energy consumption, to obtain lower latency, or to improve throughput. All proposed alternatives, however, sacrifice either trustworthiness or efficiency. In retrospect, this is not surprising. All these solutions seek to solve a notoriously difficult problem: consensus. In short, the set of nodes in the network have to agree on the same position of a block in the chain, despite the possibility of malicious behaviour of some of the nodes, or network delays. The consensus problem has been the most studied problem in distributed computing, and many impossibility and lower bound results were established. These results translate into inherent trade-offs between trust and efficiency.  In the context of our ERC AOC (Adversary-Oriented Computing) project (advanced grant), we worked on classifying distributed computing problems according to their hardness. While doing so, we revisited the issue of implementing a trustworthy payment system, i.e., the problem solved in Nakamoto’s paper.  This led us to a very interesting discovery: Current blockchain protocols are tackling a problem, i.e., consensus, which is unnecessarily strong for their purpose of building a payment system. More specifically, we have shown that it is enough to solve a problem called secure causal broadcast to implement trust in any tokenized application. This is significantly simpler than consensus. We devised a generic asynchronous protocol to solve the secure causal broadcast problem, which we called AT2, Asynchronous Trustworthy Transactions, which we patented. The goal of this project is to pave the path to its commercialization.