The Graph Level Order Unary Degree Sequence (GLOUDS) is a new succinct data structure for directed graphs that are “tree-like,” in the sense that the number of “additional” edges (w.r.t. a spanning tree) is not too high. The algorithmic idea is to represent a BFS-spanning tree of the graph (consisting of n nodes) with a well known succinct data structure for trees, named LOUDS, and enhance it with additional information that accounts for the non-tree edges. In practical tests, our data structure performs well for graphs containing up to m=5n edges, while still having competitive running times for listing adjacent nodes

The growing demand for solutions related to measurement (e.g., digital sensors, smart meters, distributed measuring systems) imposes several concerns about information and process reliability. In this context, blockchain can play a crucial role as a platform to implement applications and activities in the context of legal metrology. In most countries, the National Metrology Institutes (NMIs) are responsible for promoting these initiatives. Thus, in this paper, we present a functional architecture to integrate NMIs in a collaborative blockchain network. We discuss the main aspects and features that an inter-NMI blockchain network must deliver. Furthermore, we implement our proposal using the Hyperledger Fabric platform. We connect peers from Physikalisch-Technische Bundesanstalt (PTB) (German NMI) and the National Institute of Metrology, Quality, and Technology (Inmetro) (Brazilian NMI) in a useful application that consists of a blockchain-based public-key infrastructure to identify and authenticate smart meters. Our preliminary results demonstrate that the proposed architecture meets the main requirements imposed by applications involving measurements. Furthermore, it opens the opportunity to integrate NMIs from other countries into the project, constituting an important global initiative in the metrology field.

Embedded systems show the tendency of becoming more and more connected. This fact combined with the trend towards the Internet of Things, from which measuring instruments are not immune (e.g., smart meters), lets one assume that security in measuring instruments will inevitably play an important role soon. Additionally, measuring instruments have adopted general-purpose operating systems to offer the user a broader functionality that is not necessarily restricted towards measurement alone. In this paper, a flexible software system architecture is presented that addresses these challenges within the framework of essential requirements laid down in the Measuring Instruments Directive of the European Union. This system architecture tries to eliminate the risks general-purpose operating systems have by wrapping them, together with dedicated applications, in secure sandboxes, while supervising the communication between the essential parts and the outside world.

In the age of the Internet of Things and Industry 4.0, more and more embedded systems are connected through open networks, which also concerns measuring instruments under legal control (e.g. smart meters). Therefore, cyber-security for measuring instruments is becoming increasingly important. In this paper, possibilities to design secure measuring software running on general-purpose operating systems are analyzed according to legal requirements set up by European Directives, e.g., the Measuring Instruments Directive (2014/32/EU), which define the mandatory security level. Technical interpretations for the security concepts described in this paper are derived from these legal requirements with the aim to provide manufacturers the architectural guidance to construct systems which easily pass a conformity assessment at a Notified Body. In this paper security concepts, i.e., SELinux, AppArmor and Mandatory Integrity Control (MIC) are being described, which are based on Mandatory Access Control (MAC) strategies. Additionally, high-security methodologies and concepts, e.g., MILS and security kernels, are highlighted. In the examples given, software separation, which enhances overall security, is achieved by using SELinux mechanisms in the modules (virtual machines) atop a separation kernel.