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Rationals vs Byzantines in Consensus-based Blockchains

France

In this paper, we analyze Byzantine fault-tolerant blockchain from a game-theoretic perspective. When the process exhibits rational or Byzantine behavior, our work is the first to model the Byzantine-tolerant blockchain as a committee coordination game. Our first contribution is to provide a game-theoretic approach for analyzing the equilibrium interactions between Byzantine and rational committee members in a Byzantine-fault-tolerant blockchain. Byzantine processes aim to cause the maximum damage to the system, while rational processes respond optimally to maximize their expected net benefits. Our second contribution is to derive the conditions under which consensus is achieved or not. When the majority threshold is lower than the ratio of Byzantine processes, invalid blocks are accepted in equilibrium. When the majority threshold is very high, the equilibrium may involve coordination failure, where no invalid blocks are accepted. However, if the cost of accepting invalid blocks is very high, and they are actually valid, there may exist an equilibrium where valid blocks are accepted.

Probabilistic Smart Contracts: Secure Randomness on the Blockchain

IST Austria & Sharif University of Technology, Iran

In today's programmable blockchains, smart contracts are limited to deterministic and non-probabilistic logic. Considering various types of real-world financial contracts (such as casino games and lotteries), which are completely dependent on randomness, the lack of randomness is a significant limitation. As a result, several methods have been developed for generating randomness in smart contracts. These include ideas like using oracles or relying on block hashes. However, these methods are manipulable, meaning their outputs can be influenced by potentially non-neutral parties (e.g., oracle owners or miners). We propose a novel game-theoretic method for generating provably unmanipulable pseudo-random numbers on the blockchain. Our method allows smart contracts to obtain a reliable randomness source without relying on potentially compromised miners or oracles, enabling the creation of a new generation of smart contracts that are not limited to non-probabilistic logic and can provide more general probabilistic functionality.

This article was originally published on: CN Blog