Security analysis of a cyber-physical system

Cyber-Physical Systems (CPSs) are an integration of computing and physical processes. Information flow is an inherent property of CPSs and is of particular interest at their cyber-physical boundaries. This thesis focuses on discovering information flow properties and proposes a process to model the information flow in CPSs. A Cooperating FACTS Power System serves as a tangible example to illustrate modeling information flow using the proposed process. The proposed process can be used to model the information flow security, help analyze current information flow security requirements, and aid in the design of further security policies in CPS --Abstract, page iii

DAG-Based Attack and Defense Modeling: Don't Miss the Forest for the Attack Trees

This paper presents the current state of the art on attack and defense modeling approaches that are based on directed acyclic graphs (DAGs). DAGs allow for a hierarchical decomposition of complex scenarios into simple, easily understandable and quantifiable actions. Methods based on threat trees and Bayesian networks are two well-known approaches to security modeling. However there exist more than 30 DAG-based methodologies, each having different features and goals. The objective of this survey is to present a complete overview of graphical attack and defense modeling techniques based on DAGs. This consists of summarizing the existing methodologies, comparing their features and proposing a taxonomy of the described formalisms. This article also supports the selection of an adequate modeling technique depending on user requirements

WPSE: Fortifying Web Protocols via Browser-Side Security Monitoring

We present WPSE, a browser-side security monitor for web protocols designed to ensure compliance with the intended protocol flow, as well as confidentiality and integrity properties of messages. We formally prove that WPSE is expressive enough to protect web applications from a wide range of protocol implementation bugs and web attacks. We discuss concrete examples of attacks which can be prevented by WPSE on OAuth 2.0 and SAML 2.0, including a novel attack on the Google implementation of SAML 2.0 which we discovered by formalizing the protocol specification in WPSE. Moreover, we use WPSE to carry out an extensive experimental evaluation of OAuth 2.0 in the wild. Out of 90 tested websites, we identify security flaws in 55 websites (61.1%), including new critical vulnerabilities introduced by tracking libraries such as Facebook Pixel, all of which fixable by WPSE. Finally, we show that WPSE works flawlessly on 83 websites (92.2%), with the 7 compatibility issues being caused by custom implementations deviating from the OAuth 2.0 specification, one of which introducing a critical vulnerability

Securing Distributed Systems: A Survey on Access Control Techniques for Cloud, Blockchain, IoT and SDN

Access Control is a crucial defense mechanism organizations can deploy to meet modern cybersecurity needs and legal compliance with data privacy. The aim is to prevent unauthorized users and systems from accessing protected resources in a way that exceeds their permissions. The present survey aims to summarize state-of-the-art Access Control techniques, presenting recent research trends in this area. Moreover, as the cyber-attack landscape and zero-trust networking challenges require organizations to consider their Information Security management strategies carefully, in this study, we present a review of contemporary Access Control techniques and technologies being discussed in the literature and the various innovations and evolution of the technology. We also discuss adopting and applying different Access Control techniques and technologies in four upcoming and crucial domains: Cloud Computing, Blockchain, the Internet of Things, and Software-Defined Networking. Finally, we discuss the business adoption strategies for Access Control and how the technology can be integrated into a cybersecurity and network architecture strategy

Twenty years of rewriting logic

AbstractRewriting logic is a simple computational logic that can naturally express both concurrent computation and logical deduction with great generality. This paper provides a gentle, intuitive introduction to its main ideas, as well as a survey of the work that many researchers have carried out over the last twenty years in advancing: (i) its foundations; (ii) its semantic framework and logical framework uses; (iii) its language implementations and its formal tools; and (iv) its many applications to automated deduction, software and hardware specification and verification, security, real-time and cyber-physical systems, probabilistic systems, bioinformatics and chemical systems

Obstructions in Security-Aware Business Processes

This Open Access book explores the dilemma-like stalemate between security and regulatory compliance in business processes on the one hand and business continuity and governance on the other. The growing number of regulations, e.g., on information security, data protection, or privacy, implemented in increasingly digitized businesses can have an obstructive effect on the automated execution of business processes. Such security-related obstructions can particularly occur when an access control-based implementation of regulations blocks the execution of business processes. By handling obstructions, security in business processes is supposed to be improved. For this, the book presents a framework that allows the comprehensive analysis, detection, and handling of obstructions in a security-sensitive way. Thereby, methods based on common organizational security policies, process models, and logs are proposed. The Petri net-based modeling and related semantic and language-based research, as well as the analysis of event data and machine learning methods finally lead to the development of algorithms and experiments that can detect and resolve obstructions and are reproducible with the provided software

Ouroboros Chronos: Permissionless Clock Synchronization via Proof-of-Stake

Clock synchronization allows parties to establish a common notion of global time by leveraging a weaker synchrony assumption, i.e., local clocks with approximately the same speed. The problem has long been a prominent goal for fault-tolerant distributed computing with a number of ingenious solutions in various settings. However, despite intensive investigation, the existing solutions do not apply to common blockchain protocols, which are designed to tolerate variable---and potentially adversarial---participation patterns, e.g., sleepiness and dynamic availability. Furthermore, because such blockchain protocols rely on freshly joining (or re-joining) parties to have a common notion of time, e.g., a global clock which allows knowledge of the current protocol round, it is not clear if or how they can operate without such a strong synchrony assumption. In this work, we show how to solve the global synchronization problem by leveraging proof of stake (PoS). Concretely, we design and analyze a PoS blockchain protocol in the above dynamic-participation setting, that does not require a global clock but merely assumes that parties have local clocks advancing at approximately the same speed. Central to our construction is a novel synchronization mechanism that can be thought as the blockchain-era analogue of classical synchronizers: It enables joining parties---even if upon joining their local time is off by an arbitrary amount---to quickly calibrate their local clocks so that they all show approximately the same time. As a direct implication of our blockchain construction---since the blockchain can be joined and observed by any interested party---we obtain a permissionless PoS implementation of a global clock that may be used by higher level protocols that need access to global time