time and resilient master clocks in cyber physical systems

Since many years, it has been acknowledged that the role of time is fundamental to the design of distributed algorithms [21]. This is exacerbated in cyber-physical distributed systems, and consequently in Systems-of-Systems, where it is sometimes impossible to say which one of two observed environmental events occurred first

Cyber-Physical Systems of Systems: Foundations – A Conceptual Model and Some Derivations: The AMADEOS Legacy

Computer Systems Organization and Communication Networks; Software Engineering; Complex Systems; Information Systems Applications (incl. Internet); Computer Application

Robustness of Attack-Resilient State Estimators

The interaction between information technology and physical world makes Cyber-Physical Systems (CPS) vulnerable to malicious attacks beyond the standard cyber attacks. This has motivated the need for attack-resilient state estimation. Yet, the existing state-estimators are based on the non-realistic assumption that the exact system model is known. Consequently, in this work we present a method for state estimation in presence of attacks, for systems with noise and modeling errors. When the the estimated states are used by a state-based feedback controller, we show that the attacker cannot destabilize the system by exploiting the difeerence between the model used for the state estimation and the real physical dynamics of the system. Furthermore, we describe how implementation issues such as jitter, latency and synchronization errors can be mapped into parameters of the state estimation procedure that describe modeling errors, and provide a bound on the state-estimation error caused by modeling errors. This enables mapping control performance requirements into real-time (i.e., timing related) specifications imposed on the underlying platform. Finally, we illustrate and experimentally evaluate this approach on an unmanned ground vehicle case-study

GNSS Related Threats to Power Grid Applications

As power grid environments are moving towards the smart grid vision of the future, the traditional schemes for power grid protection and control are making way for new applications. The advancements in this field have made the requirements for power grid’s time synchronization accuracy and precision considerably more demanding. So far, the signals provided by Global Navigation Satellite Systems have generally addressed the need for highly accurate and stable reference time in power grid applications. These signals however are highly susceptible to tampering as they are being transmitted. Since electrical power transmission and distribution are critical functions for any modern society, the risks and impacts affiliated with satellite-based time synchronization in power grids ought to be examined. This thesis aims to address the matter. The objective is to examine how Global Navigation Satellite Systems are utilized in the power grids, how different attacks would potentially be carried out by employing interference and disturbance to GNSS signals and receivers and how the potential threats can be mitigated. A major part of the research is done through literature review, and the core concepts and different implementations of Global Navigation Satellite Systems are firstly introduced. The literature review also involves the introduction of different power grid components and subsystems, that utilize Global Positioning System for time synchronization. Threat modeling techniques traditionally practiced in software development are applied to power grid components and subsystems to gain insight about the possible threats and their impacts. The threats recognized through this process are evaluated and potential techniques for mitigating the most notable threats are presented.Sähköverkot ovat siirtymässä kohti tulevaisuuden älykkäitä sähköverkkoja ja perinteiset sähköverkon suojaus- ja ohjausmenetelmät tekevät tilaa uusille sovelluksille. Alan kehitys on tehnyt aikasynkronoinnin tarkkuusvaatimuksista huomattavasti aikaisempaa vaativampia. Tarkka aikareferenssi sähköverkoissa on tähän saakka saavutettu satelliittinavigointijärjestelmien tarjoamien signaalien avulla. Nämä signaalit ovat kuitenkin erittäin alttiita erilaisille hyökkäyksille. Sähkönjakelujärjestelmät ovat kriittinen osa nykyaikaista yhteiskuntaa ja riskejä sekä seuraamuksia, jotka liittyvät satelliittipohjaisten aikasynkronointimenetelmien hyödyntämiseen sähköverkoissa, tulisi tarkastella. Tämä tutkielma pyrkii vastaamaan tähän tarpeeseen. Päämääränä on selvittää, miten satelliittinavigointijärjestelmiä hyödynnetään sähköverkoissa, kuinka erilaisia hyökkäyksiä voidaan toteuttaa satelliittisignaaleja häiritsemällä ja satelliittisignaalivastaanottimia harhauttamalla ja kuinka näiden muodostamia uhkia voidaan lieventää. Valtaosa tästä tutkimuksesta on toteutettu kirjallisuuskatselmoinnin pohjalta. Työ kattaa satelliittinavigointijärjestelmien perusteet ja esittelee erilaisia tapoja, kuinka satelliittisignaaleja hyödynnetään sähköverkoissa erityisesti aikasynkronoinnin näkökulmasta. Työssä hyödynnettiin perinteisesti ohjelmistokehityksessä käytettyjä uhkamallinnusmenetelmiä mahdollisten uhkien ja seurausten analysointiin. Lopputuloksena esitellään riskiarviot uhkamallinnuksen pohjalta tunnistetuista uhkista, sekä esitellään erilaisia menettelytapoja uhkien lieventämiseksi

Detection and Mitigation of Cyber Attacks on Time Synchronization Protocols for the Smart Grid

The current electric grid is considered as one of the greatest engineering achievements of the twentieth century. It has been successful in delivering power to consumers for decades. Nevertheless, the electric grid has recently experienced several blackouts that raised several concerns related to its availability and reliability. The aspiration to provide reliable and efficient energy, and contribute to environment protection through the increasing utilization of renewable energies are driving the need to deploy the grid of the future, the smart grid. It is expected that this grid will be self-healing from power disturbance events, operating resiliently against physical and cyber attack, operating efficiently, and enabling new products and services. All these call for a grid with more Information and Communication Technologies (ICT). As such, power grids are increasingly absorbing ICT technologies to provide efficient, secure and reliable two-way communication to better manage, operate, maintain and control electric grid components. On the other hand, the successful deployment of the smart grid is predicated on the ability to secure its operations. Such a requirement is of paramount importance especially in the presence of recent cyber security incidents. Furthermore, those incidents are subject to an augment with the increasing integration of ICT technologies and the vulnerabilities they introduce to the grid. The exploitation of these vulnerabilities might lead to attacks that can, for instance, mask the system observability and initiate cascading failures resulting in undesirable and severe consequences. In this thesis, we explore the security aspects of a key enabling technology in the smart grid, accurate time synchronization. Time synchronization is an immense requirement across the domains of the grid, from generation to transmission, distribution, and consumer premises. We focus on the substation, a basic block of the smart grid system, along with its recommended time synchronization mechanism - the Precision Time Protocol (PTP) - in order to address threats associated with PTP, and propose practical and efficient detection, prevention, mitigation techniques and methodologies that will harden and enhance the security and usability of PTP in a substation. In this respect, we start this thesis with a security assessment of PTP that identifies PTP security concerns, and then address those concerns in the subsequent chapters. We tackle the following main threats associated with PTP: 1) PTP vulnerability to fake timestamp injection through a compromised component 2) PTP vulnerability to the delay attack and 3) The lack of a mechanism that secures the PTP network. Next, and as a direct consequence of the importance of time synchronization in the smart grid, we consider the wide area system to demonstrate the vulnerability of relative data alignment in Phasor Data Concentrators to time synchronization attacks. These problems will be extensively studied throughout this thesis, followed by discussions that highlight open research directions worth further investigations