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Aigner, A., Khelil, A..  2020.  An Effective Semantic Security Metric for Industrial Cyber-Physical Systems. 2020 IEEE Conference on Industrial Cyberphysical Systems (ICPS). 1:87—92.

The emergence of Industrial Cyber-Physical Systems (ICPS) in today's business world is still steadily progressing to new dimensions. Although they bring many new advantages to business processes and enable automation and a wider range of service capability, they also propose a variety of new challenges. One major challenge, which is introduced by such System-of-Systems (SoS), lies in the security aspect. As security may not have had that significant role in traditional embedded system engineering, a generic way to measure the level of security within an ICPS would provide a significant benefit for system engineers and involved stakeholders. Even though many security metrics and frameworks exist, most of them insufficiently consider an SoS context and the challenges of such environments. Therefore, we aim to define a security metric for ICPS, which measures the level of security during the system design, tests, and integration as well as at runtime. For this, we try to focus on a semantic point of view, which on one hand has not been considered in security metric definitions yet, and on the other hand allows us to handle the complexity of SoS architectures. Furthermore, our approach allows combining the critical characteristics of an ICPS, like uncertainty, required reliability, multi-criticality and safety aspects.

Ullah, S., Shetty, S., Hassanzadeh, A..  2018.  Towards Modeling Attacker’s Opportunity for Improving Cyber Resilience in Energy Delivery Systems. 2018 Resilience Week (RWS). :100–107.
Cyber resiliency of Energy Delivery Systems (EDS) is critical for secure and resilient cyber infrastructure. Defense-in-depth architecture forces attackers to conduct lateral propagation until the target is compromised. Researchers developed techniques based on graph spectral matrices to model lateral propagation. However, these techniques ignore host criticality which is critical in EDS. In this paper, we model attacker's opportunity by developing three criticality metrics for each host along the path to the target. The first metric refers the opportunity of attackers before they penetrate the infrastructure. The second metric measure the opportunity a host provides by allowing attackers to propagate through the network. Along with vulnerability we also take into account the attributes of hosts and links within each path. Then, we derive third criticality metric to reflect the information flow dependency from each host to target. Finally, we provide system design for instantiating the proposed metrics for real network scenarios in EDS. We present simulation results which illustrates the effectiveness of the metrics for efficient defense deployment in EDS cyber infrastructure.
Amoroso, E., Merritt, M..  1994.  Composing system integrity using I/O automata. Tenth Annual Computer Security Applications Conference. :34—43.
The I/O automata model of Lynch and Turtle (1987) is summarized and used to formalize several types of system integrity based on the control of transitions to invalid starts. Type-A integrity is exhibited by systems with no invalid initial states and that disallow transitions from valid reachable to invalid states. Type-B integrity is exhibited by systems that disallow externally-controlled transitions from valid reachable to invalid states, Type-C integrity is exhibited by systems that allow locally-controlled or externally-controlled transitions from reachable to invalid states. Strict-B integrity is exhibited by systems that are Type-B but not Type-A. Strict-C integrity is exhibited by systems that are Type-C but not Type-B. Basic results on the closure properties that hold under composition of systems exhibiting these types of integrity are presented in I/O automata-theoretic terms. Specifically, Type-A, Type-B, and Type-C integrity are shown to be composable, whereas Strict-B and Strict-C integrity are shown to not be generally composable. The integrity definitions and compositional results are illustrated using the familiar vending machine example specified as an I/O automaton and composed with a customer environment. The implications of the integrity definitions and compositional results on practical system design are discussed and a research plan for future work is outlined.
Xu, Zhiheng, Ng, Daniel Jun Xian, Easwaran, Arvind.  2019.  Automatic Generation of Hierarchical Contracts for Resilience in Cyber-Physical Systems. 2019 IEEE 25th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA). :1–11.

With the growing scale of Cyber-Physical Systems (CPSs), it is challenging to maintain their stability under all operating conditions. How to reduce the downtime and locate the failures becomes a core issue in system design. In this paper, we employ a hierarchical contract-based resilience framework to guarantee the stability of CPS. In this framework, we use Assume Guarantee (A-G) contracts to monitor the non-functional properties of individual components (e.g., power and latency), and hierarchically compose such contracts to deduce information about faults at the system level. The hierarchical contracts enable rapid fault detection in large-scale CPS. However, due to the vast number of components in CPS, manually designing numerous contracts and the hierarchy becomes challenging. To address this issue, we propose a technique to automatically decompose a root contract into multiple lower-level contracts depending on I/O dependencies between components. We then formulate a multi-objective optimization problem to search the optimal parameters of each lower-level contract. This enables automatic contract refinement taking into consideration the communication overhead between components. Finally, we use a case study from the manufacturing domain to experimentally demonstrate the benefits of the proposed framework.

Straub, Jeremy.  2019.  Cyber Mutual Assured Destruction as a System of Systems and the Implications for System Design. 2019 14th Annual Conference System of Systems Engineering (SoSE). :137—139.

Mutual assured destruction is a Cold War era principle of deterrence through causing your enemy to fear that you can destroy them to at least the same extent that they can destroy you. It is based on the threat of retaliation and requires systems that can either be triggered after an enemy attack is launched and before the destructive capability is destroyed or systems that can survive an initial attack and be launched in response. During the Cold War, the weapons of mutual assured destructions were nuclear. However, with the incredible reliance on computers for everything from power generation control to banking to agriculture logistics, a cyber attack mutual assured destruction scenario is plausible. This paper presents this concept and considers the deterrent need, to prevent such a crippling attack from ever being launched, from a system of systems perspective.

Qiu, Tongsheng, Wang, Xianyi, Tian, Yusen, Du, Qifei, Sun, Yueqiang.  2019.  A System Design of Real-Time Narrowband Rfi Detection And Mitigation for Gnss-R Receiver. IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium. :5167–5170.

With the rapid development of radio detection and wireless communication, narrowband radio-frequency interference (NB-RFI) is a serious threat for GNSS-R (global navigation satellite systems - reflectometry) receivers. However, interferometric GNSS-R (iGNSS-R) is more prone to the NB-RFIs than conventional GNSS-R (cGNSS-R), due to wider bandwidth and unclean replica. Therefore, there is strong demand of detecting and mitigating NB-RFIs for GNSS-R receivers, especially iGNSS-R receivers. Hence, focusing on working with high sampling rate and simplifying the fixed-point implementation on FPGA, this paper proposes a system design exploiting cascading IIR band-stop filters (BSFs) to suppress NB-RFIs. Furthermore, IIR BSF compared with IIR notch filter (NF) and IIR band-pass filter (BPF) is the merely choice that is able to mitigate both white narrowband interference (WNBI) and continuous wave interference (CWI) well. Finally, validation and evaluation are conducted, and then it is indicated that the system design can detect NB-RFIs and suppress WNBI and CWI effectively, which improves the signal-to-noise ratio (SNR) of the Delay-Doppler map (DDM).

Quan, Guocong, Tan, Jian, Eryilmaz, Atilla.  2019.  Counterintuitive Characteristics of Optimal Distributed LRU Caching Over Unreliable Channels. IEEE INFOCOM 2019 - IEEE Conference on Computer Communications. :694–702.
Least-recently-used (LRU) caching and its variants have conventionally been used as a fundamental and critical method to ensure fast and efficient data access in computer and communication systems. Emerging data-intensive applications over unreliable channels, e.g., mobile edge computing and wireless content delivery networks, have imposed new challenges in optimizing LRU caching systems in environments prone to failures. Most existing studies focus on reliable channels, e.g., on wired Web servers and within data centers, which have already yielded good insights with successful algorithms on how to reduce cache miss ratios. Surprisingly, we show that these widely held insights do not necessarily hold true for unreliable channels. We consider a single-hop multi-cache distributed system with data items being dispatched by random hashing. The objective is to achieve efficient cache organization and data placement. The former allocates the total memory space to each of the involved caches. The latter decides data routing strategies and data replication schemes. Analytically we characterize the unreliable LRU caches by explicitly deriving their asymptotic miss probabilities. Based on these results, we optimize the system design. Remarkably, these results sometimes are counterintuitive, differing from the ones obtained for reliable caches. We discover an interesting phenomenon: asymmetric cache organization is optimal even for symmetric channels. Specifically, even when channel unreliability probabilities are equal, allocating the cache spaces unequally can achieve a better performance. We also propose an explicit unequal allocation policy that outperforms the equal allocation. In addition, we prove that splitting the total cache space into separate LRU caches can achieve a lower asymptotic miss probability than resource pooling that organizes the total space in a single LRU cache. These results provide new and even counterintuitive insights that motivate novel designs for caching systems over unreliable channels. They can potentially be exploited to further improve the system performance in real practice.
Ramadan, Q., Salnitriy, M., Strüber, D., Jürjens, J., Giorgini, P..  2017.  From Secure Business Process Modeling to Design-Level Security Verification. 2017 ACM/IEEE 20th International Conference on Model Driven Engineering Languages and Systems (MODELS). :123–133.

Tracing and integrating security requirements throughout the development process is a key challenge in security engineering. In socio-technical systems, security requirements for the organizational and technical aspects of a system are currently dealt with separately, giving rise to substantial misconceptions and errors. In this paper, we present a model-based security engineering framework for supporting the system design on the organizational and technical level. The key idea is to allow the involved experts to specify security requirements in the languages they are familiar with: business analysts use BPMN for procedural system descriptions; system developers use UML to design and implement the system architecture. Security requirements are captured via the language extensions SecBPMN2 and UMLsec. We provide a model transformation to bridge the conceptual gap between SecBPMN2 and UMLsec. Using UMLsec policies, various security properties of the resulting architecture can be verified. In a case study featuring an air traffic management system, we show how our framework can be practically applied.