Variabilities in the execution time of integrated circuits are frequently exploited as a side channel attack to expose secret information of deployed systems. Standard countermeasures analyze and change the explicit timing behavior in lower level hardware description languages, but their application is time consuming and error-prone. In this paper we investigate the integration of timing attack resilience into the high-level synthesis (HLS). HLS translates programs expressed in higher level programming languages, such as C, seamlessly to synthesizable hardware. We use timing annotations of basic blocks in C to add scheduling constraints that in the synthesis process balance the execution time of security-related execution branches. We integrate our approach to the scheduling of the open source LegUp HLS tool and apply the proposed method for the asymmetric cryptography algorithms RSA and ECC. The results proof the resistance against timing attacks, with a negligible overhead in synthesis efforts, area, and run-time.

A good cyber-physical-systems (CPS) design methodology must conduct trade-off analysis of both the physical characteristics of the CPS as well as its cyber sub-system in a holistic manner. This paper presents a design space exploration (DSE) approach for CPSs that emphasizes the variabilities of the physical subsystem and control aspects of the system. We propose the application of parameterizable physical models and automatic recalculation of control algorithm parameters for the explored systems. The resulting parameterizable models can be applied in a systematic simulation-based DSE framework that facilitates the identification of superior system configurations. We applied the proposed design flow to a real non-linear inverted pendulum system with a range of physical and cyber settings. The results show the feasibility and effectiveness of our approach in the design of physical and control parts of CPSs. Our work supplements existing work on cyber system modeling and plays an integral part in the design automation of such systems.

Cyber Physical Systems (CPSs) integrate networked embedded computation systems with real-world physical installations. Programming of CPSs is not trivial, since CPSs combine traditional programming challenges and real-world timing, concurrency, and communication. This paper shows how a programming framework that allows students to implement and test CPS control programs in their Internet browsers, can improve both the students' learning experience and learning results. Students model and program a CPS application on a high abstraction level in a web page. This web page, provided by the instructor, invokes the student's code either together with the CPS as functional specification models in a virtual timing environment, or as component in a real-world system that interacts with a real remote physical implementation. Using the provided abstraction, students can incrementally design a CPS and experience challenges such as channel delays, model uncertainties, and real-time behavior, but without the need for complex low level programming or tools. For a CPS example system, we applied the framework in an embedded system design class. Our results show, the ability of a JavaScript-based programming and execution environment to design, program, and run CPSs on different levels of abstraction. Our results also indicate an increased approval from the students and a significantly improved understanding of modeling and programming in the class.

Constraint programming solvers, such as Satisfiability Modulo Theory (SMT) solvers, are capable tools in finding preferable configurations for embedded systems from large design spaces. However, constructing SMT constraint programs is not trivial, in particular for complex systems that exhibit multiple viewpoints and models. In thisarticle we propose CoDeL: a component-based description language that allows system designers to express components as reusable building blocks of the system with their parameterizable properties, models, and interconnectivity. Systems are synthesized by allocating, connecting, and parameterizing the components to satisfy the requirements of an application. We present an algorithm that transforms component-based design spaces, expressible in CoDeL, to an SMT program, which, solved by state-of-the-art SMT solvers, determines the satisfiability of the synthesis problem, and delivers a correct-by-construction system configuration. Evaluation results for use cases in the domain of scheduling and mapping of distributed real-time processes confirm, first, the performance gain of SMT compared to traditional design space exploration approaches, second, the usability gains by expressing design problems in CoDeL, and third, the capability of the CoDeL/SMT approach to support the design of embedded systems.

In this paper we outline a novel approach for accessing mutually exclusive resources in hierarchically scheduled real-time systems. Our method known as the Resource Access Control Protocol with Preemption (RACPwP) is an improved resource allocation protocol which utilizes preemptive critical sections to provide guaranteed determinism for hard real-time tasks and comparable response times for soft real-time tasks. Our experiments demonstrated that RACPwP outperforms other state-of-the-art resource access control protocols used in hierarchically scheduled systems. RACPwP was implemented as part of VxWorks and evaluated in an actual embedded application used in the aerospace industry. As a result, the response times for hard real-time tasks were improved over a traditional resource synchronization protocol.

The wireless Bluetooth standard, generally used for short range point-to-point communication between mobile devices, can in principle connect any number of stations into a multi-hop network. For this purpose a "scatternet" must be built up, which is a collection of small overlapping "piconets". Bluetooth technology is basically well-suited to some types of wireless sensor networks, but such deployment has been been limited due to the difficulty in setting up and maintaining a scatternet. We demonstrate the SFX algorithm, an extension of the earlier SHAPER procedure. The SFX algorithm builds up a scatternet by a decentralized procedure with the properties of self-organization, self-optimization, and self-healing. The procedure has been verified by deployment in a photovoltaic power plant.

Wireless sensor and actor networks based on Bluetooth technology require an algorithm to build up and maintain a Bluetooth scatternet. Although much research has been done, actual deployment is rare because a self-organizing and self-healing procedure suitable for actual Bluetooth nodes has not yet been developed. We present the SFX algorithm to build a scatternet tree with the required properties. The method was verified by simulations for up to 400 nodes and by field tests.

This paper describes a two-step process to infer specific technical constraints and parameters needed for a reliable mission-specific design of wireless sensor networks (WSN). As the first step, we propose a new requirement catalog helping end-users to formulate a complete and consistent specification of WSN mission requirements. Its generality allows the unambiguous characterization of a wide spectrum of applications from the end-user's perspective. As the second step, we introduce a methodology to deduce fine grained technical specifications from the general requirements. The proposed automatic graph-based requirement expansion approach translates the content of the catalog and additional requirements to specific technical terms, which provide the basis for an application-specific WSN design. A real-world use case - a new WSN application in the area of critical infrastructure protection - demonstrates the applicability of the presented approach.

We present an overview of end-to-end encryption solutions for convergecast traffic in wireless sensor networks that support in-network processing at forwarding intermediate nodes. Other than hop-by-hop based encryption approaches, aggregator nodes can perform in-network processing on encrypted data. Since it is not required to decrypt the incoming ciphers before aggregating, substantial advantages are 1) neither keys nor plaintext is available at aggregating nodes, 2) the overall energy consumption of the backbone can be reduced, 3) the system is more flexible with respect to changing routes, and finally 4) the overall system security increases. We provide a qualitative comparison of available approaches, point out their strengths, respectively weaknesses, and investigate opportunities for further research.

Wireless communication and smart sensors and actuators pose means to sustainably improve automation technology. Unfortunately they also cause an abundance of new challenges regarding security and safety of the system. After introducing the security concepts, this paper discusses an engineering methodology to cope with security requirements in context of industrial automation. Two practical examples demonstrate how the solutions even for pretty similar scenarios can differ significantly. The proposed development flow promises a reliable objective engineering of proper system solutions. Key concepts of the flow are a holistic goal description and an iterative composition algorithm that inherently applies and extends existing knowledge.

This paper shows how complex security-related design decisions in wireless sensor networks can be made less difficult with a proposed supporting tool. As case study in this paper we focus on in-network-aggregation which is a promising option to reduce network effort. We introduce several algorithms for concealed data aggregation, each with its own benefits and drawbacks concerning security issues but also with respect to code size, processing overhead etc. Selecting the optimal combination requires in-depth knowledge of programming resource constrained devices, protocols for those devices, and last but not least significant background in security. Our proposed configuration tool - named configKIT - has been designed to cope with such complexity. This paper presents how configKIT works, how it will be set up, and how it can be applied in practice. The pre-compiler assessment process considers memory, energy and security parameters and provides reliable application-dependent configurations to the developer before a single line of code is written. The approach can reduce development time significantly and enables even complex and sophisticated security algorithms to a broader public.

In this paper we discuss algorithms that allow the concealed data aggregation (CDA) in wireless sensor networks. We describe and evaluate three algorithms that were reported to suit to the WSN scenario. As result of the evaluation, where we emphasize the awareness to potential attack scenarios, we present a brief overview of strengths and weaknesses of the algorithms. Since no algorithm provides all desirable goals, we propose two approaches to cope with the problems. The first is the successive combination of two algorithms. It increases security, while the additional efforts can be minimized by carefully selected parameters. For the second approach we face specific weaknesses and engineer mechanisms that solve the particular issues. With the considered homomorphic message authentication code and a discussion of the id-issue we exemplary evaluate the two biggest issues of the very promising CMT algorithm.