Due to increased number of attacks on the Internet of Things (IoT) devices, the security of IoT networks became critical. Some recent researches proposed the adoption of blockchain in IoT networks without a thorough discussion on the impact of the solution on the devices performance. Furthermore, blockchain employment in the context of IoT can be challenging due to the devices hardware limitations. To fill this gap, this paper proposes an IoT ledger-based architecture to ensure access control on heterogeneous scenarios. This research applies conventional devices used on IoT networks, such as Arduino, Raspberry and Orange Pi boards. Finally, we perform performance evaluation focused on access control of IoT devices and on information propagation through peers on a private IoT network scenario.

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The Internet of Things (IoT) is transforming our physical world into a complex and dynamic system of connected devices on an unprecedented scale. Connecting everyday physical objects is creating new business models, improving processes and reducing costs and risks. Recently, blockchain technology has received a lot of attention from the community as a possible solution to overcome security issues in IoT. However, traditional blockchains (such as the ones used in Bitcoin and Ethereum) are not well suited to the resource-constrained nature of IoT devices and also with the large volume of information that is expected to be generated from typical IoT deployments. To overcome these issues, several researchers have presented lightweight instances of blockchains tailored for IoT. For example, proposing novel data structures based on blocks with decoupled and appendable data. However, these researchers did not discuss how the consensus algorithm would impact their solutions, i.e., the decision of which consensus algorithm would be better suited was left as an open issue. In this paper, we improved an appendable-block blockchain framework to support different consensus algorithms through a modular design. We evaluated the performance of this improved version in different emulated scenarios and studied the impact of varying the number of devices and transactions and employing different consensus algorithms. Even adopting different consensus algorithms, results indicate that the latency to append a new block is less than 161ms (in the more demanding scenario) and the delay for processing a new transaction is less than 7ms, suggesting that our improved version of the appendable-block blockchain is efficient and scalable, and thus well suited for IoT scenarios. * The first and second authors have the same contribution for the present research.

Products and services provided by modern organizations are usually designed, deployed, and supported by large-scale Information Technology (IT) infrastructures. In order to obtain the best performance out of provided products and services, it is essential that these organizations enforce rational practices for the management of resources that compose their infrastructures. For this purpose, in recent years a few standards and libraries of best practices for IT infrastructures and services management have been proposed. Among the most widely accepted proposals, in both academy and industry, is worth mentioning the Information Technology Infrastructure Library (ITIL). A common point in most of those standards and libraries is the explicit concern with the risks related to IT activities. Proactively dealing with adverse and favorable events that may arise during everyday operations might prevent, for example: delay on deployment of services, cost overrun in activities, predictable failures of handled resources, and, consequently waste of money. Although important, risk management in practice usually lacks in automation and standardization in IT environments. Generally, it is performed by stakeholders in interviews and brainstorms, which may be a very time/resource-consuming task and sometimes too imprecise to guide risk related decisions. Therefore, in this dissertation, a framework to support the automation of some key phases of risk management is proposed, aiming to make it simpler, faster, and more accurate. The proposed framework is targeted to workow-based IT management systems. The main approach is to learn from problems reported in the history of previously conducted workows in order to estimate risks for future executions. Furthermore, comprehensive and interactive risk reports are proposed aiming to ease the analysis of assessed risks by involved humans. The proposed framework had its applicability evaluated in two case studies both in IT related areas, namely: IT Change Management and IT Project Management. The results show how the framework is not only useful to speed up the risk assessment process, but also to assist the decision making of project managers and IT operators by organizing risk detailed information in a comprehensive way. In addition, the modular approach employed in the design of the proposed framework allows it to be generic enough to t in dierent contexts (changes and projects) and still customizable to adapt to more specic requirements.