Multilevel Runtime Verification for Safety and Security Critical Cyber Physical Systems from a Model Based Engineering Perspective

Advanced embedded system technology is one of the key driving forces behind the rapid growth of Cyber-Physical System (CPS) applications. CPS consists of multiple coordinating and cooperating components, which are often software-intensive and interact with each other to achieve unprecedented tasks. Such highly integrated CPSs have complex interaction failures, attack surfaces, and attack vectors that we have to protect and secure against. This dissertation advances the state-of-the-art by developing a multilevel runtime monitoring approach for safety and security critical CPSs where there are monitors at each level of processing and integration. Given that computation and data processing vulnerabilities may exist at multiple levels in an embedded CPS, it follows that solutions present at the levels where the faults or vulnerabilities originate are beneficial in timely detection of anomalies. Further, increasing functional and architectural complexity of critical CPSs have significant safety and security operational implications. These challenges are leading to a need for new methods where there is a continuum between design time assurance and runtime or operational assurance. Towards this end, this dissertation explores Model Based Engineering methods by which design assurance can be carried forward to the runtime domain, creating a shared responsibility for reducing the overall risk associated with the system at operation. Therefore, a synergistic combination of Verification & Validation at design time and runtime monitoring at multiple levels is beneficial in assuring safety and security of critical CPS. Furthermore, we realize our multilevel runtime monitor framework on hardware using a stream-based runtime verification language

Energy-Aware System-Level Design of Cyber-Physical Systems

Cyber-Physical Systems (CPSs) are heterogeneous systems in which one or several computational cores interact with the physical environment. This interaction is typically performed through electromechanical elements such as sensors and actuators. Many CPSs operate as part of a network and some of them present a constrained energy budget (for example, they are battery powered). Examples of energy constrained CPSs could be a mobile robot, the nodes that compose a Body Area Network or a pacemaker. The heterogeneity present in the composition of CPSs together with the constrained energy availability makes these systems challenging to design. A way to tackle both complexity and costs is the application of abstract modelling and simulation. This thesis proposed the application of modelling at the system level, taking energy consumption in the different kinds of subsystems into consideration. By adopting this cross disciplinary approach to energy consumption it is possible to decrease it effectively. The results of this thesis are a number of modelling guidelines and tool improvements to support this kind of holistic analysis, covering energy consumption in electromechanical, computation and communication subsystems. From a methodological point of view these have been framed within a V-lifecycle. Finally, this approach has been demonstrated on two case studies from the medical domain enabling the exploration of alternative systems architectures and producing energy consumption estimates to conduct trade-off analysis

Cyber-security for embedded systems: methodologies, techniques and tools

L'abstract è presente nell'allegato / the abstract is in the attachmen

Towards a Taxonomy for Eliciting Design-Operation Continuum Requirements of Cyber-Physical Systems

Software systems that are embedded in autonomous Cyber-Physical Systems (CPSs) usually have a large life-cycle, both during its development and in maintenance. This software evolves during its life-cycle in order to incorporate new requirements, bug fixes, and to deal with hardware obsolescence. The current process for developing and maintaining this software is very fragmented, which makes developing new software versions and deploying them in the CPSs extremely expensive. In other domains, such as web engineering, the phases of development and operation are tightly connected, making it possible to easily perform software updates of the system, and to obtain operational data that can be analyzed by engineers at development time. However, in spite of the rise of new communication technologies (e.g., 5G) providing an opportunity to acquire Design-Operation Continuum Engineering methods in the context of CPSs, there are still many complex issues that need to be addressed, such as the ones related with hardware-software co-design. Therefore, the process of Design-Operation Continuum Engineering for CPSs requires substantial changes with respect to the current fragmented software development process. In this paper, we build a taxonomy for Design-Operation Continuum Engineering of CPSs based on case studies from two different industrial domains involving CPSs (elevation and railway). This taxonomy is later used to elicit requirements from these two case studies in order to present a blueprint on adopting Design-Operation Continuum Engineering in any organization developing CPSs

Simulation-based testing of highly configurable cyber-physical systems: automation, optimization and debugging

Sistema Ziber-Fisikoek sistema ziber digitalak sistema fisikoekin uztartzen dituzte. Sistema hauen aldakortasuna handitzen ari da erabiltzaileen hainbat behar betetzeko. Ondorioz, sistema ziber-fisikoa aldakorrak edota produktu lerroak ari dira garatzen eta sistema hauek milaka edo milioika konfiguraziotan konfiguratu daitezke. Sistema ziber-fisiko aldakorren test eta balidazioa prozesua garestia da, batez ere probatu beharreko konfigurazio kopuruaren ondorioz. Konfigurazio kopuru altuak sistemaren prototipo bat erabiltzea ezinezkoa egiten du. Horregatik, sistema ziber-fisiko aldagarriak simulazio modeloak erabilita probatzen dira. Hala ere, simulazio bidez sistema ziber-fisikoak probatzea erronka izaten jarraitzen du. Hasteko, simulazio denbora altua izaten da normalki, software-az aparte, sistema fisikoa simulatu behar delako. Sistema fisiko hau normalean modelo matematiko konplexuen bitartez modelatzen da, konputazionalki garestia delarik. Jarraitzeko, sistema ziber-fisikoek ingeniaritzaren domeinu ezberdinak dituzte tartean, adibidez mekanika edo elektronika. Domeinu bakoitzak bere simulazio erremienta erabiltzen du, eta erremienta guzti hauek interkonektatzeko ko-simulazioa erabiltzen da. Nahiz eta ko-simulazioa abantaila bat izan ematen duen flexibilitateagatik, simulagailu ezberdinen erabilerak simulazio denbora handiagotzen du. Azkenik, sistema ziber-fisikoak simulaziopean probatzean, probak maila ezberdinetan egin behar dira (adb., Model, Software eta Hardware-in-the-Loop mailak), eta honek, proba-kasuak exekutatzeko denbora handitzen du. Tesi honen helburua sistema ziber-fisiko aldakorren test jardunbideak hobetzea da, horretarako automatizazio, optimizazio eta arazketa metodoak proposatzen ditu. Automatizazioari dagokionez, lehenengo, erremienta-bidezko metodologia bat proposatzen da. Metodologia hau test sistema instantziak automatikoki sortzeko gai da, test sistema hauek sistema ziber-fisiko aldagarrien konfigurazioak automatikoki probatzeko gai dira (adb., test orakuluen bitartez). Bigarren, test frogak automatikoki sortzeko planteamendu bat proposatzen da helburu anitzeko bilaketa algoritmoak erabilita. Optimizazioari dagokionez, test frogen aukeraketarako planteamendu bat eta test frogen priorizaziorako beste planteamendu bat proposatzen dira, biak bilaketa alix goritmoak erabiliz, sistema ziber-fisiko aldakorrak test maila ezberdinetan probatzeko helburuarekin. Arazketari dagokionez, “espektroan oinarritutako falten lokalizazioa” izeneko teknika bat produktu lerroen testuingurura adaptatu da, eta faltak isolatzeko metodo bat proposatzen da. Honek, falta ezberdinak lokalizatzea errezten du ez bakarrik sistema ziber-fisiko aldakorretan, baizik eta edozein produktu lerrotan non “feature model” delako modeloak erabiltzen diren aldakortasuna kudeatzeko.Los sistemas cyber-físicos (CPSs) integran tecnologías digitales con procesos físicos. La variabilidad de estos sistemas está creciendo para responder a la demanda de diferentes clientes. Como consecuencia de ello, los CPSs están volviéndose configurables e incluso líneas de producto, lo que significa que pueden ser configurados en miles y millones de configuraciones. El testeo de sistemas cyber-físicos configurables es un proceso costoso, en general debido a la cantidad de configuraciones que han de ser testeadas. El número de configuraciones a testear hace imposible el uso de un prototipo del sistema. Por ello, los sistemas CPSs configurables están siendo testeadas utilizando modelos de simulación. Sin embargo, el testeo de sistemas cyber-físicos bajo simulación sigue siendo un reto. Primero, el tiempo de simulación es normalmente largo, ya que, además del software, la capa física del CPS ha de ser testeada. Esta capa física es típicamente modelada con modelos matemáticos complejos, lo cual es computacionalmente caro. Segundo, los sistemas cyber-físicos implican el uso de diferentes dominios de la ingeniería, como por ejemplo la mecánica o la electrónica. Por ello, para interconectar diferentes herramientas de modelado y simulación hace falta el uso de la co-simulación. A pesar de que la co-simulación es una ventaja en términos de flexibilidad para los ingenieros, el uso de diferentes simuladores hace que el tiempo de simulación sea más largo. Por último, al testear sistemas cyberfísicos haciendo uso de simulación, existen diferentes niveles (p.ej., Model, Software y Hardware-in-the-Loop), lo cual incrementa el tiempo para ejecutar casos de test. Esta tesis tiene como objetivo avanzar en la práctica actual del testeo de sistemas cyber-físicos configurables, proponiendo métodos para la automatización, optimización y depuración. En cuanto a la automatización, primero, se propone una metodología soportada por una herramienta para generar automáticamente instancias de sistemas de test que permiten testear automáticamente configuraciones del sistema CPS configurable (p.ej., haciendo uso de oráculos de test). Segundo, se propone un enfoque para generación de casos de test basado en algoritmos de búsqueda multiobjetivo, los cuales generan un conjunto de casos de test. En cuanto a la optimización, se propone un enfoque para selección y otro para priorización de casos de test, ambos basados en algoritmos de búsqueda, de cara a testear eficientemente sistemas cyberfísicos configurables en diferentes niveles de test. En cuanto a la depuración, se adapta una técnica llamada “Localización de Fallos Basada en Espectro” al contexto de líneas de productos y proponemos un método de aislamiento de fallos. Esto permite localizar bugs no solo en sistemas cyber-físicos configurables sino también en cualquier línea de producto donde se utilicen modelos de características para gestionar la variabilidad.Cyber-Physical Systems (CPSs) integrate digital cyber technologies with physical processes. The variability of these systems is increasing in order to give solution to the different customers demands. As a result, CPSs are becoming configurable or even product lines, which means that they can be set into thousands or millions of configurations. Testing configurable CPSs is a time consuming process, mainly due to the large amount of configurations that need to be tested. The large amount of configurations that need to be tested makes it infeasible to use a prototype of the system. As a result, configurable CPSs are being tested using simulation. However, testing CPSs under simulation is still challenging. First, the simulation time is usually long, since apart of the software, the physical layer needs to be simulated. This physical layer is typically modeled with complex mathematical models, which is computationally very costly. Second, CPSs involve different domains, such as, mechanical and electrical. Engineers of different domains typically employ different tools for modeling their subsystems. As a result, co-simulation is being employed to interconnect different modeling and simulation tools. Despite co-simulation being an advantage in terms of engineers flexibility, the use of different simulation tools makes the simulation time longer. Lastly, when testing CPSs employing simulation, different test levels exist (i.e., Model, Software and Hardware-in-the-Loop), what increases the time for executing test cases. This thesis aims at advancing the current practice on testing configurable CPSs by proposing methods for automation, optimization and debugging. Regarding automation, first, we propose a tool supported methodology to automatically generate test system instances that permit automatically testing configurations of the configurable CPS (e.g., by employing test oracles). Second, we propose a test case generation approach based on multi-objective search algorithms that generate cost-effective test suites. As for optimization, we propose a test case selection and a test case prioritization approach, both of them based on search algorithms, to cost-effectively test configurable CPSs at different test levels. Regarding debugging, we adapt a technique named Spectrum-Based Fault Localization to the product line engineering context and propose a fault isolation method. This permits localizing bugs not only in configurable CPSs but also in any product line where feature models are employed to model variability

Runtime observable and adaptable UML state machine-based software components generation and verification: [email protected] approach

Cyber-Physical Systems (CPSs) are embedded computing systems in which computation interacts closely with the physical world through sensors and actuators. CPSs are used to control context aware systems. These types of systems are complex systems that will have different configurations and their control strategy can be configured depending the environmental data and current situation of the context. Therefore, in current industrial environments, the software of embedded and Cyber-Physical systems have to cope with increasing complexity, uncertain scenarios and safe requirements at runtime. The UML State Machine is a powerful formalism to model the logical behaviour of these types of systems, and in Model Driven Engineering (MDE) we can generate code automatically from these models. MDE aims to overcome the complexity of software construction by allowing developers to work at the high-level models of software systems instead of low-level codes. However, determining and evaluating the runtime behaviour and performance of models of CPSs using commercial MDE tools is a challenging task. Such tools provide little support to observe at model-level the execution of the code generated from the model, and to collect the runtime information necessary to, for example, check whether defined safe properties are met or not. One solution to address these requirements is having the software components information in model terms at runtime ([email protected]). Work on [email protected] seeks to extend the applicability of models produced in MDE approaches to the runtime environment. Having the model at runtime is the first step towards the runtime verification. Runtime verification can be performed using the information of model elements (current state, event, next state,etc.) This thesis aims at advancing the current practice on generating automatically Unified Modeling Language - State Machine (UML-SM) based software components that are able to provide their internal information in model terms at runtime. Regarding automation, we propose a tool supported methodology to automatically generate these software components. As for runtime monitoring, verification and adaptation, we propose an externalized runtime module that is able to monitor and verify the correctness of the software components based on their internal status in model terms at component and system level. In addition, if an error is detected, the runtime adaptation module is activated and the safe adaptation process starts in the involved software components. All things considered, the overall safe level of the software components and CPSs is enhanced.Sistema Ziber-Fisikoak, konputazio sistema txertatuez osatuta daude. Konputazio sistema txertatu hauek, mundu birtuala mundu fisikoarekin uztartzeko gaitasuna eskaintzen dute. Sistema ziberfisikoak orokorrean sistema konplexuak izan ohi dira eta inguruan gertazen denaren araberako konfigurazio desberdinak izan ohi dituzte. Gaur egungo industria ingurunetan, sistema hauek daramaten kontroleko softwarea asko handitu da eta beren konplexutasunak ere gorakada handia izan du: aurrez ezagunak ez diren baldintza eta inguruetan lan egin beharra dute askotan, denbora errealeko eskakizunak eta segurtasun eskakizunak ere beteaz. UML State Machine formalismoa, goian aipaturiko sistema mota horien portaera logikoa modelizatzeko erabiltzen den formalismo indartsu bat da. Formalismo honen baitan eta Model Driven Engineering (MDE) enfokea jarraituaz, sistema modelatzeko erabilitako grafikoetatik sisteman txertatua izango den kodea automatikoki sor genezake. MDEk softwarea sortzeko orduan izan genezakeen konplexutasuna gainditu nahi du, garatzailei software-sistemen goi-mailako ereduetan lan egiteko aukera emanez. Hala ere, MDE-an oinarrituriko tresna komertzialak erabiliaz, zaila izaten da berauen bidez sorturiko kodearen errendimendua eta portaera sistema exekuzioan dagoenean ebaluatzea. Tresna horiek laguntza gutxi eskaintzen dute modelotatik sortutako kodea exekutatzen ari denean sisteman zer gertatzen ari denaren informazioa modeloaren terminoetan jasotzeko. Beraz, exekuzio denboran, oso zaila izaten da sistemaren portaera egokia den edo ez aztertzea modelo mailako informazio hori erabiliaz. Eskakizun horiek kudeatzeko modu bat, software modeloaren informazioa denbora errealean izatea da ([email protected] enfokea). [email protected] enfokearen helburu nagusietako bat, MDE enfokearekin garapen fasean sortutako modeloak exekuzio denboran (runtime-en) erabilgarri izatean datza. Exekuzio denboran egiaztapen edo testing-a egin ahal izateko lehen urratsa, testeatu nahi den software horren modeloa exekuzio denboran eskuragarri izatea da. Honela, exekuzio denborako egiaztapen edo berifikazioak softwarea modelatzeko erabili ditugun elementu berberak erabiliaz egin daitke (egungo egoera, gertaera, hurrengo egoera, eta abar). Tesi honen helburutako bat UML-State Machine modeloetan oinarritutako eta exekuzio denboran beren barne egoeraren informazioa modeloko elementu bidez probestu ahalko duten software osagaiak modu automatikoan sortzea da. Automatizazioari dagokionez, lehenik eta behin, software-osagai horiek automatikoki sortzen dituzten tresnak eskaintzen dituen metodologia proposatzen dugu. Bigarrenik, UMLSM oinarritutako software osagaiak automatikoki sortuko dituen herraminta bera proposatzen dugu. Exekuzio denboran eguneraketen jarraipenari, egiaztatzeari eta egokitzeari dagokionez, barne egoera UML-SM modelo terminoetan eskaintzen duten software osagaiak egiaztatzeko eta egokitzeko gai den kanpo exekuzio modulo bat proposatzen dugu. Honela, errore bat detektatzen bada, exekuzio garaian egokitze modulua aktibatuko da egokitzapen prozesu segurua martxan jarriaz. Honek, dagokion software osagaiari abixua bidaliko dio egokitzapena egin dezan. Gauza guztiak kontuan hartuta, software osagaien eta CPSen segurtasun maila orokorra hobetua izango da.Los sistemas cyber-físicos (CPSs) son sistemas de computación embebidos en los que la computación interactúa estrechamente con el mundo físico a través de sensores y actuadores. Los CPS se utilizan para controlar sistemas que proveen conocimiento del contexto. Este tipo de sistemas son sistemas complejos que suelen tener diferentes configuraciones y su estrategia de control puede configurarse en función de los datos del entorno y de la situación actual del contexto. Por lo tanto, en los entornos industriales actuales, el software de los sistemas embebidos tiene que hacer frente a la creciente complejidad, los escenarios inciertos y los requisitos de seguridad en tiempo de ejecución. Las máquinas de estado UML son un formalismo muy utilizado en industria para modelar el comportamiento lógico de este tipo de sistemas, y siguiendo el enfoque Model Driven Engineering (MDE) podemos generar código automáticamente a partir de estos modelos. El objetivo de MDE es superar la complejidad de la construcción de software permitiendo a los desarrolladores trabajar en los modelos de alto nivel de los sistemas de software en lugar de tener que codificar el control mediante lenguajes de programación de bajo nivel. Sin embargo, determinar y evaluar el comportamiento y el rendimiento en tiempo de ejecución de estos modelos generados mediante herramientas comerciales de MDE es una tarea difícil. Estas herramientas proporcionan poco apoyo para observar a nivel de modelo la ejecución del código generado a partir del modelo. Por lo tanto, no son muy adecuadas para poder recopilar la información de tiempo de ejecución necesaria para, por ejemplo, comprobar si se cumplen o no las restricciones definidas. Un enfoque para gestionar estos requisitos, es tener la información de los componentes de software en términos de modelo en tiempo de ejecución ([email protected]). El trabajo en [email protected] busca ampliar la aplicabilidad de los modelos producidos en fase de desarrollo mediante el enfoque MDE al entorno de tiempo de ejecución. Tener el modelo en tiempo de ejecución es el primer paso para poder llevar a cabo la verificación en tiempo de ejecución. Así, esta verificación se podrá realizar utilizando la información de los elementos del modelo (estado actual, evento, siguiente estado, etc.). El objetivo de esta tesis es avanzar en la práctica actual de generar automáticamente componentes software basados en Unified Modeling Language - State Machine (UML-SM) que sean capaces de proporcionar información interna en términos de modelos en tiempo de ejecución. En cuanto a la automatización, en primer lugar, proponemos una metodología soportada por herramientas para generar automáticamente estos componentes de software. En segundo lugar, proponemos un marco de trabajo de generación de componentes de software basado en UML-SM. En cuanto a la monitorización, verificación y adaptación en tiempo de ejecución, proponemos un módulo de tiempo de ejecución externalizado que es capaz de monitorizar y verificar la validez de los componentes del software en función de su estado interno en términos de modelo. Además, si se detecta un error, se activa el módulo de adaptación en tiempo de ejecución y se inicia el proceso de adaptación seguro en el componente de software correspondiente. Teniendo en cuenta todo esto, el nivel de seguridad global de los componentes del software y de los CPS se ve mejorado

High-Level Analysis of the Impact of Soft-Faults in Cyberphysical Systems

As digital systems grow in complexity and are used in a broader variety of safety-critical applications, there is an ever-increasing demand for assessing the dependability and safety of such systems, especially when subjected to hazardous environments. As a result, it is important to identify and correct any functional abnormalities and component faults as early as possible in order to minimize performance degradation and to avoid potential perilous situations. Existing techniques often lack the capacity to perform a comprehensive and exhaustive analysis on complex redundant architectures, leading to less than optimal risk evaluation. Hence, an early analysis of dependability of such safety-critical applications enables designers to develop systems that meets high dependability requirements. Existing techniques in the field often lack the capacity to perform full system analyses due to state-explosion limitations (such as transistor and gate-level analyses), or due to the time and monetary costs attached to them (such as simulation, emulation, and physical testing). In this work we develop a system-level methodology to model and analyze the effects of Single Event Upsets (SEUs) in cyberphysical system designs. The proposed methodology investigates the impacts of SEUs in the entire system model (fault tree level), including SEU propagation paths, logical masking of errors, vulnerability to specific events, and critical nodes. The methodology also provides insights on a system's weaknesses, such as the impact of each component to the system's vulnerability, as well as hidden sources of failure, such as latent faults. Moreover, the proposed methodology is able to identify and categorize the system's components in order of criticality, and to evaluate different approaches to the mitigation of such criticality (in the form of different configurations of TMR) in order to obtain the most efficient mitigation solution available. The proposed methodology is also able to model and analyze system components individually (system component level), in order to more accurately estimate the component's vulnerability to SEUs. In this case, a more refined analysis of the component is conducted, which enables us to identify the source of the component's criticality. Thereafter, a second mitigation mechanic (internal to the component) takes place, in order to evaluate the gains and costs of applying different configurations of TMR to the component internally. Finally, our approach will draw a comparison between the results obtained at both levels of analysis in order to evaluate the most efficient way of improving the targeted system design

Proceedings of the 11th Overture Workshop

The 11th Overture Workshop was held in Aarhus, Denmark on Wed/Thu 28–29th Au- gust 2013. It was the 11th workshop in the current series focusing on the Vienna De- velopment Method (VDM) and particularly its community-based tools development project, Overture (http://www.overturetool.org/), and related projects such as COMPASS(http://www.compass-research.eu/) and DESTECS (http://www.destecs.org). Invited talks were given by Yves Ledru and Joe Kiniry. The workshop attracted 25 participants representing 10 nationalities. The goal of the workshop was to provide a forum to present new ideas, to identify and encourage new collaborative research, and to foster current strands of work towards publication in the mainstream conferences and journals. The Overture initiative held its first workshop at FM’05. Workshops were held subsequently at FM’06, FM’08 and FM’09, FM’11, FM’12 and in between