@phdthesis{Brzozowski2012, author = {Brzozowski, Marcin}, title = {Energy-efficient means to support short end-to-end delays in wireless sensor networks}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-25299}, school = {BTU Cottbus - Senftenberg}, year = {2012}, abstract = {This work addresses tough challenges of sensor network applications with Quality of Service requirements. That is, nodes must work with batteries for a long time, support short end-to-end delays and robust communication in multi-hop networks. It starts with presenting previous research efforts that address such challenges. For instance, many Medium Access Control (MAC) protocols keep nodes mostly sleeping to save energy and synchronize wake-up times for communication. Although such protocols offer short end-to-end delays, they still suffer from long idle listening and shortened lifetimes. The main reasons are the long time needed to detect an idle channel and inefficient ways of dealing with clock drift. This work introduces novel solutions to these problems, mainly at Layer 2 of the OSI model, that significantly reduce idle listening. First, nodes predict future drift and reduce the time needed to compensate clock uncertainty among neighbors. Second, they quickly detect an idle channel and power down the transceiver. In some scenarios, nodes work 30\% longer owing to these solutions. To tackle problems with unreliable wireless links, sensor nodes may apply various solutions at Layer 2. For example, with Automatic Repeat reQuest (ARQ) protocol they send retries on frame losses, resulting in extra energy consumption. This work examines the impact of ARQ on the lifetime and on the reception rate. Several indoor and outdoor experiments showed that with only 1-2 retries nodes can handle many communication problems. Besides, owing to the idle-listening reduction, mentioned previously, ARQ shortens the lifetime by 10\% only. Although this work addresses particular applications, the solutions presented here can be used in other scenarios and with different protocols. For instance, the energy-efficient drift compensation approach can be directly used in any schedule-based MAC protocols, like the one based on the IEEE 802.15.4 standard. Besides, any protocol can benefit from the solution to the idle-listening reduction based on the early detection of idle channel. Finally, owing to the analytical model that estimates the lifetime of nodes, researches and developers can early evaluate MAC protocols running on various hardware platforms.}, subject = {Rechnernetz; Drahtloses Sensorsystem; Verteiltes System; Kommunikationsprotokoll; Drahtlose Kommunikation; Sensornetze; Kurze Latenzen; Uhrendrift; Medienzugriff; Wireless communication; Sensor networks; Short delay; Clock drift; MAC}, language = {en} } @misc{Vogel2018, type = {Master Thesis}, author = {Vogel, Elisabeth}, title = {Analyse von EM-Kartographie als Mittel zur Bestimmung von Leakage-Quellen sowie des Effektes geeigneter Gegenmaßnahmen}, doi = {10.26127/BTUOpen-6454}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-64545}, school = {BTU Cottbus - Senftenberg}, year = {2018}, abstract = {The Internet of Things (IoT) and Wireless Sensor Networks (WSNs) are essential for today's global information society, relying on small wireless devices for networking. When these devices' functionalities or data are manipulated, the potential damage is significant. Hence, securing data transmission between these devices using cryptography is crucial. However, the security of cryptographic algorithms depends on the secrecy of cryptographic keys, which can be vulnerable due to physical accessibility. Side-channel analysis attacks can exploit this vulnerability by using physical parameters associated with the operation of cryptographic chips, such as electromagnetic radiation during cryptographic operations. In response to this challenge, the Leakage Source Cartography Tool (LSC-Tool) was developed in this thesis to expedite the analysis of electromagnetic radiation in IHP's elliptic curve cryptography designs. The LSC-Tool enables automated evaluation of sets of electromagnetic traces, obtained from different measurement positions across a cryptographic chip. The analysis results in a leakage source map (LS-map) that displays the success of electromagnetic analysis attacks at each measurement point. This tool offers a cost-effective and rapid means to assess the resistance of cryptographic designs against attacks, providing designers with insights into the most vulnerable areas of the chip and information about leakage per clock cycle. By applying the LSC-Tool, the resistance of two IHP ECC designs against horizontal differential electromagnetic analysis attacks was tested across 25 measurement positions. The statistical analysis of traces can be conducted using three methods: the least squares method, the difference-of-means-test, or the difference-of-the-mean method. The generated LS-maps show that using different methods yields distinct leakage source indications. Combining these maps enhances the attack's success rate. Notably, during this research, it became evident that the LSC-Tool could be adapted to create LS-maps for the functional blocks of ECC designs, enabling the analysis of simulated power traces for IHP ECC designs.}, subject = {EM-Kartographie; Elliptische Kurven; Power Analysis Angriffe; Seitenkanalattacke; Fehleranalyse; Kryptosystem; Elektromagnetische Strahlung; Elliptische Kurve; Side-channel-analysis; Countermeasures; Power analysis}, language = {de} } @misc{AlpirezBock2015, type = {Master Thesis}, author = {Alpirez Bock, Estuardo}, title = {SCA resistent implementation of the Montgomery kP-algorithm}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-36288}, school = {BTU Cottbus - Senftenberg}, year = {2015}, abstract = {Mathematically, cryptographic approaches are secure. This means that the time an attacker needs for finding the secret by brute forcing these approaches is about the time of the existence of our world. Practically, an algorithm implemented in hardware is a device that generates a lot of additional data during the calculation process. Its power consumption, electromagnetic radiation, etc. can be measured, saved and analysed for key extraction. Such attacks are called side channel analysis attacks and are significant threats when applying cryptographic algorithms. By considering these attacks when implementing a cryptographic algorithm, it is possible to design an implementation that is more resistant against them. The goal of this thesis was to design a methodology to securely implement the Montgomery kP-operation using an IHP implementation as a starting point. In addition, the area and energy consumption of the secure Montgomery kP-multiplier should still be highly efficient. The resistance against power analysis attacks of two different IHP ECC implementations was analysed in this thesis. A horizontal power analysis attack using the difference-of-means test was performed with the goal of finding potential leakage sources exploited in side channel analysis attacks, i.e. finding the reasons of a correct extraction of the cryptographic key. For both analysed ECC designs, four key candidates were extracted with a correctness of 90\% or more. Through analysis of the implemented Montgomery kP-algorithm's functionality and its power consumption, it was established that the algorithm's operation execution flow was the main cause of the implementations' vulnerability. Thus, a design methodology consisting in changing the Montgomery kP-algorithm operation flow was developed. As a result, the re-designed implementations do not deliver any correctly extracted key candidates whenever the difference-of-means test is performed on them. These re-designs implied an increase on the chip area by about 5\% for each implementation. The execution time needed for performing a complete kP-operation was reduced for both designs. Thereby one implementation's execution time was reduced by 12\% in comparison to its original version and even though its power consumption was increased by 9\%, its energy consumption per kP-operation was reduced by 4.5\%.}, subject = {Side channel analysis; Elliptic curve cryptography; Power analysis; Difference-of-means test; Elliptic curve point multiplication; Elliptische Kurve; Kryptologie}, language = {en} } @phdthesis{SojkaPiotrowska2016, author = {Sojka-Piotrowska, Anna}, title = {On the applicability of short key asymmetric cryptography in low power wireless sensor networks}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-39453}, school = {BTU Cottbus - Senftenberg}, year = {2016}, abstract = {The growing popularity of Wireless Sensor Networks (WSN) makes the spectrum of their applications very wide. A great number of the application areas like health monitoring or military applications require a high level of security and dependability from the wireless sensor network. Solving these issues can be supported by providing cryptographic solutions into WSN applications. Since the WSNs mainly consist of low power devices, cryptographic solutions ideal for WSNs should provide computationally lightweight security mechanisms producing small data packets and ensuring confidentiality. Cryptographic mechanisms that have both these features are considered in this thesis, which main objective is the analysis of the applicability of the short key elliptic curve cryptography in WSN environments. Reduced key lengths require modification of the standard ECC security algorithms to provide authentication and also a novel solution for a cryptographic secure pseudo-random number generator. The proposed solution is based on the standard ECC, but it differs in several aspects. The main difference is that the parameters of the used elliptic curve have to be kept secret. This is due to the fact that solving the Discreet Logarithm Problem (DLP) for such short parameters can be done in short time. Additionally, using shorter parameters for the underlying elliptic curves excludes also the use of standard hash functions, what mainly influences the mechanisms for generating the digital signature. Hash functions require large input values and produce relatively large output data that is inapplicable in the shortECC environment. Thus, within this thesis a modified version of standard Elliptic Curves Digital Signature Algorithm is proposed, which does not require any hash function. The shortECC needs pseudo-random numbers in the encryption and the digital signature protocols, but since it operates on numbers that are significantly shorter than the ones used by other cryptographic approaches, pseudo-random number generators for standard approaches are not suitable for shortECC. Thus, the new pseudo-random number generator not involving any additional hardware besides the modules available on the used test platform and operating on 32-bit long integers, is proposed. The randomness of the numbers generated by the proposed algorithm and their applicability for cryptographic purposes was evaluated using the NIST test suites. The shortECC approach was also subjected to cryptanalysis in order to proof its security and determine the circumstances and constraints for its application.}, subject = {ECC; Sensor Networks; PRNG; Lightweight cryptography; Elliptische Kurven; Drahtlose Sensornetze; Zufallszahl Generator; Drahtloses Sensorsystem; Zufallsgenerator}, language = {en} }