Análise de mecanismos para consenso distribúıdo aplicados a Blockchain

The Blockchain concept has recently emerged as an alternative approach for e-commerce payment, based on decentralized systems that do not rely on trusted institutions. Actually, since Blockchain was first proposed for use in cryptocurrencies, several solutions have appeared that employ this technology in a variety of domains, such as creating distributed registries of smart contracts. Whichever the target application domain, though, solutions implementing Blockchain use a set of well-known technologies, such as encryption, Merkle Trees, P2P networks, and consensus mechanisms. The latter are of particular research interest today, since most consensus mechanisms used in the early cryptocurrencies (e.g., Bitcoin) involve considerable computational power to ensure system consistency. Aiming to evaluate the state of the art on the area, this manuscript reviews Blockchain concepts and classifications, focusing specifically on the underlying consensus mechanisms and security aspects of the resulting solutions. We also describe a brief experiment using Ethereum and MultiChain, aiming to analyze security aspects of the Practical Byzantine Fault Tolerance (PBFT) and Proof-of-Work (PoW) consensus approaches.