The Internet of Things (IoT) is increasingly a reality today. Nevertheless, some key challenges still need to be given particular attention so that IoT solutions further support the growing demand for connected devices and the services offered. Due to the potential relevance and sensitivity of services, IoT solutions should address the security and privacy concerns surrounding these devices and the data they collect, generate, and process. Recently, the Blockchain technology has gained much attention in IoT solutions. Its primary usage scenarios are in the financial domain, where Blockchain creates a promising applications world and can be leveraged to solve security and privacy issues. However, this emerging technology has a great potential in the most diverse technological areas and can significantly help achieve the Internet of Things view in different aspects, increasing the capacity of decentralization, facilitating interactions, enabling new transaction models, and allowing autonomous coordination of the devices. The paper goal is to provide the concepts about the structure and operation of Blockchain and, mainly, analyze how the use of this technology can be used to provide security and privacy in IoT. Finally, we present the stalker, which is a selfish miner variant that has the objective of preventing a node to publish its blocks on the main chain.
Blockchain é um banco de dados distribuído que mantém uma lista de transações em uma estrutura de dados chamada bloco, que ligados ao seu anterior, formam uma cadeia de blocos. Foi proposto com a finalidade de facilitar transações financeiras, seguras, públicas e auditáveis. No entanto, possui aplicação em diversas áreas e está sujeita a ataques.Um dos ataques mais conhecidos é a mineração egoísta que, sob certas condições, pode resultar em uma parcela desproporcional de recompensas a atacantes que se desviam do comportamento honesto. O objetivo deste artigo é apresentar e analisar o Stalker, uma estratégia de mineração egoísta com o objetivo de impedir a publicação de um bloco ou transação específica. Resultados mostram que a eficácia do ataque é proporcional à relação entre o poder computacional do atacante e do alvo.
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