Steffen Peter

How public key cryptography influences wireless sensor node lifetime

In this paper we try to estimate the real influence of public key cryptography (PKC) to the lifetime of a sensor node in wireless sensor networks. We investigate four types of nodes; MICA2DOT, MICA2, MICAz and TelosB. For all these nodes we estimate the power consumption for most common RSA and ECC operations, i.e., signature generation and verification as well as key exchange mechanisms. We also estimate the power consumed by the transmission of their results. Our results show that the application of strong cryptography is feasible. Even for the most constrained node performing the ECC-160 signature once every 10 minutes increases the duty cycle only by about 0.5 per cent, i.e., the influence to the lifetime is not significant. Nevertheless, the public key cryptography shall be used with care.

A Survey on Concepts, Applications, and Challenges in Cyber-Physical Systems

The Cyber-Physical System (CPS) is a term describing a broad range of complex, multi-disciplinary, physically-aware next generation engineered system that integrates embedded computing technologies (cyber part) into the physical world. In order to define and understand CPS more precisely, this article presents a detailed survey of the related work, discussing the origin of CPS, the relations to other research fields, prevalent concepts, and practical applications. Further, this article enumerates an extensive set of technical challenges and uses specific applications to elaborate and provide insight into each specific concept. CPS is a very broad research area and therefore has diverse applications spanning different scales. Additionally, the next generation technologies are expected to play an important role on CPS research. All of CPS applications need to be designed considering the cutting-edge technologies, necessary system-level requirements, and overall impact on the real world.

tinyDSM: A highly reliable cooperative data storage for Wireless Sensor Networks

The advantage of a Wireless Sensor Network (WSN) compared to a centric approach is the distribution of sensing suites. However, in order for such a system of distributed resources to work in a reliable and effective way a smart cooperation between nodes is needed. In this paper we propose a middleware approach for a highly reliable data storage that helps to assure data availability despite the well known WSN resource problems and disappearing or inactive nodes by providing a reasonable data redundancy in the system. Such a solution helps to ease the design and optimization of the data exchange between nodes as well. Our solution is configurable in order to satisfy the needs of the application on top regarding performance/requirements trade-off. The options specify the quantity and quality of the data replication. Additional features like event mechanism that monitors the data and the possibility to issue database like queries increase the applicability of our middleware. In this paper we focus on the evaluation of its capabilities regarding reliability, the consistency of replicates and the costs of the data management. The simulation results for a reasonable set-up show that the CPU load caused by the data replication is low (below 3 percent) and the average inconsistency time is as small as about 0,06 seconds for a single hop and about 0,15 seconds for a two hops replication area. There is still room for improvements, but a clear definition of problems helps to find ways to cope with them in order to achieve the chosen goals.

Public key cryptography empowered smart dust is affordable

Public Key Cryptography (PKC), although very beneficial for key distribution, authentication and other related issues, was for a long time considered as too expensive for small, battery-powered and resource-constrained devices. In the recent years, first research groups started to cope with the challenges applying PKC in such environments. One of the results is that Elliptic Curve Cryptography (ECC) fits here perfectly, providing the level of security RSA does, but with much shorter keys. In this paper, we evaluate the power consumption induced by various PKC approaches including calculation and transmission costs. Our results clearly show that hardware accelerators significantly reduce the energy consumption and prolong lifetime of sensor nodes. Our solution for 163 bit ECC needs only 1.02 mm² cell area in a 0.25 µm technology and only 12.8 µWs per point multiplication. Due to its small size it can be manufactured for about 0.05 USD in mass production.

On Concealed Data Aggregation for WSNs

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. I. MOTIVATION

Design of Secure ECG-Based Biometric Authentication in Body Area Sensor Networks.

Body area sensor networks (BANs) utilize wireless communicating sensor nodes attached to a human body for convenience, safety, and health applications. Physiological characteristics of the body, such as the heart rate or Electrocardiogram (ECG) signals, are promising means to simplify the setup process and to improve security of BANs. This paper describes the design and implementation steps required to realize an ECG-based authentication protocol to identify sensor nodes attached to the same human body. Therefore, the first part of the paper addresses the design of a body-area sensor system, including the hardware setup, analogue and digital signal processing, and required ECG feature detection techniques. A model-based design flow is applied, and strengths and limitations of each design step are discussed. Real-world measured data originating from the implemented sensor system are then used to set up and parametrize a novel physiological authentication protocol for BANs. The authentication protocol utilizes statistical properties of expected and detected deviations to limit the number of false positive and false negative authentication attempts. The result of the described holistic design effort is the first practical implementation of biometric authentication in BANs that reflects timing and data uncertainties in the physical and cyber parts of the system.

An efficient polynomial multiplier in GF(2 m ) and its application to ECC designs

This paper discusses approaches that allow constructing efficient polynomial multiplication units. Such multipliers are the most important components of ECC hardware accelerators. The proposed hRAIK multiplication improves energy consumption, the longest path, and required silicon area compared to state of the art approaches. The authors use such a core multiplier to construct an efficient sequential polynomial multiplier based on the known iterative Karatsuba method. Finally, the authors exploit the beneficial properties of the design to build an ECC accelerator. The design for GF(2233) requires about 1.4 mm2 cell area in a 0.25mum technology and needs 80 musec for an EC point multiplication

Bluetooth Scatternet Tree Formation for Wireless Sensor Networks

A method for information exchange between Bluetooth nodes, the method comprising the Bluetooth nodes, without establishing a new Bluetooth connection in accordance with a Bluetooth standard, repeatedly requesting, receiving and accumulating state information from different neighbor nodes in their respective neighborhood of Bluetooth nodes by means of inquiry and extended inquiry response messages, the state information provided in response to a request comprising a tree identifier indicative of a tree, to which the respective neighbor node currently belongs, a depth information element indicative of a depth of the respective neighbor node in the respective tree and a descendant information element indicative of a number of descendants managed by the respective neighbor node.

Sensor node processor for security applications

In this paper we present a sensor node processor designed to support complex data encryption/decryption operations. The system is developed around an asynchronous processor core supported by AES, ECC and SHA-1 crypto accelerators. The paper describes the chip architecture and its components and gives the chip implementation details. Finally, the power and performance of the chip have been discussed and analyzed.

In-network-aggregation as case study for a support tool reducing the complexity of designing secure wireless sensor networks

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.