MDP-Based Quantitative Analysis Framework for Proof of Authority

The widespread recognition of the blockchain technology that decoupled from the cryptocurrency has raised the interest of the industry. As the apparent drawbacks of the Proof of Work (PoW) protocol hinder the large deployment of PoW protocol for many distributed applications, the consensus mechanism evolved quickly to satisfy the business requirements. Since the consensus mechanism is the core of the blockchain technology, it is imperative to ensure that it performs correctly. Proof of Authority, a novel Byzantine fault-tolerant algorithm, is an appealing alternative to PoW algorithm for its high throughput rate and the security. However, the PoA protocol seems to do not convince the public about its security as it lacks adequate analysis. In this paper, we firstly explored the balance between security and scalability of PoA protocol, and subsequently, we proposed a flexible quantitative analysis framework based on Markov Decision Process. The framework can be used to indicate the security from the perspective of the adversarial optimal strategies. To capture the action strategies of an adversary, we also presented a formal model of PoA and its attack model. Since the modeling process for a blockchain protocol is not a trivial task, we implemented a case study to demonstrate the modeling process and discussed the security provisions of a specific PoA protocol.