Finality is crucial for the security and scalability of blockchains. As shards are added and larger data is stored, blockchain users want to be certain that whatever is written to the chain cannot be reverted.

Finality in Casper CBC is an emergent property of message-passing communication in the network. Validators become final on decisions with some degree of finality - the number of faults that must have occured to facilitate valid proposal of contradictory decisions. As more communication supporting a decision is observed, a higher degree of finality is attained.

However, testing for finality is a hard problem. As messages form a complex network, naively finding a pattern of messages such that desired finality properties are satisfied is computationally expensive.

This project innovates on two counts:

  1. We present a state-of-the-art, efficient algorithm for the CBC Casper framework to detect different degrees of finality, produced in Javascript for this submission. The algorithm supports consensus on binary decisions, but can be trivially extended to blocks under any latest message-driven fork choice rule.

  2. We produce a visual explanation of the algorithm and the theory supporting it, making the research uniquely accessible to client developers, researchers keen to work on the same and a technical audience that is not specialised in blockchain technologies. The visual essay is written in HTML/JS, with React/D3 used as front-end libraries. Large message logs are simulated and shown in the essay.

We invite the jury to read our visual essay at the link provided below (http://hackingresear.ch/cbc-finality/index.html). We also offer the code of our finality test in a Github repository.

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