Secure and Private Data Aggregation in WSN

Data aggregation is an important efficiency mechanism for large scale, resource constrained networks such as wireless sensor networks (WSN). Security and privacy are central for many data aggregation applications: (1) entities make decisions based on the results of the data aggregation, so the entities need to be assured that the aggregation process and in particular the aggregate data they receive has not been corrupted (i.e., verify the integrity of the aggregation); (2) If the aggregation application has been attacked, then the attack must be handled efficiently; (3) the privacy requirements of the sensor network must be preserved. The nature of both wireless sensor networks and data aggregation make it particularly challenging to provide the desired security and privacy requirements: (1) sensors in WSN can be easily compromised and subsequently corrupted by an adversary since they are unmonitored and have little physical security; (2) a malicious aggregator node at the root of an aggregation subtree can corrupt not just its own value but also that of all the nodes in its entire aggregation subtree; (3) since sensors have limited resourced, it is crucial to achieve the security objectives while adopting only cheap symmetric-key based operations and minimizing communication cost. In this thesis, we first address the problem of efficient handling of adversarial attacks on data aggregation applications in WSN. We propose and analyze a detection and identification solution, presenting a precise cost-based characterization when in-network data aggregation retains its assumed benefits under persistent attacks. Second, we address the issue of data privacy in WSN in the context of data aggregation. We introduce and analyze the problem of privacy-preserving integrity-assured data aggregation (PIA) and show that there is an inherent tension between preservation of data privacy and secure data aggregation. Additionally, we look at the problem of PIA in publish-subscribe networks when there are multiple, collaborative yet competing subscribers

A self-organized dynamic clustering method and its multiple access mechanism for multiple WBANs

Due to its wide application range and attractive features, wireless body area networks (WBANs) is considered as a revolutionary technology, which is envisaged to change how people manage and think about their health and their life styles. In this paper, we propose a self-organized dynamic clustering (SDC) method and its multiple access mechanism to mitigate the interference and improve the QoS in multiple WBANs environment. To the best of our knowledge, this is the first paper that focuses on the spectrum allocation for multiple WBANs. We borrow the concepts of cell and cluster from cellular networks to allocate the channels for different WBANs. The clustering is self-organized to improve the data transmission for intra-WBAN communication by the information exchange via inter-WBAN communication. Additionally, based on the cluster architecture, an inter-WBAN relaying (IWR) protocol for packets with low privacy or high reliability is also investigated. The simulation results show that SDC has better signal to interference ratio compared with existing framework. Besides, SDC and IWR also provide better QoS performance in terms of higher data packet delivery ratio and lower packet delay

Comparison of authentication schemes for wireless sensor networks as applied to secure data aggregation

Il processo di aggregazione è fondamentale nell'economia energetica di una rete di sensori wireless (WSN). Tale processo, però, pone delle nuove sfide sul piano della sicurezza, dettate dagli stringenti vincoli di complessità tipici di una WSN. In questa tesi, in particolare, si indaga l'applicabilità degli algoritmi di autenticazione al contesto dell'aggregazion

Cryptographic key management for the vehicles of tomorrow

The automotive industry is undergoing a major transformation process in which nearly every part of the vehicle is becoming digital and connected. Modern vehicles are often connected to the internet, feature several wireless interfaces and will soon communicate directly with surrounding vehicles and roadside infrastructure using V2X technology. However, this transformation has not yet been paralleled by the development of techniques or standards which address the cyber security challenges posed by these systems. The automotive industry has historically failed to use secure cryptography or appropriate key management techniques and there is no sign that things have improved. In this thesis, we present several new cryptographic and key management flaws in an existing automotive immobiliser system and we develop two new V2X architectures for improving the safety and privacy of tomorrow’s connected and autonomous vehicles. Specifically, we study the AUT64 automotive block cipher and its associated authentication protocol in a real-world immobiliser system. Despite having a 120~bit key, we find a number of flaws in the system which we combine to present several practical key-recovery attacks. Our first new V2X architecture, IFAL, provides a practical and secure improvement to the leading European standard for V2X. IFAL introduces a new certificate issuance mechanism that eliminates the trade-off between pseudonym duration and bandwidth. Our second architecture, VDAA, addresses the need for efficient techniques that preserve vehicle privacy despite dishonest or colluding certificate authorities

Design and Analysis of Security Schemes for Low-cost RFID Systems

With the remarkable progress in microelectronics and low-power semiconductor technologies, Radio Frequency IDentification technology (RFID) has moved from obscurity into mainstream applications, which essentially provides an indispensable foundation to realize ubiquitous computing and machine perception. However, the catching and exclusive characteristics of RFID systems introduce growing security and privacy concerns. To address these issues are particularly challenging for low-cost RFID systems, where tags are extremely constrained in resources, power and cost. The primary reasons are: (1) the security requirements of low-cost RFID systems are even more rigorous due to large operation range and mass deployment; and (2) the passive tags' modest capabilities and the necessity to keep their prices low present a novel problem that goes beyond the well-studied problems of traditional cryptography. This thesis presents our research results on the design and the analysis of security schemes for low-cost RFID systems. Motivated by the recent attention on exploiting physical layer resources in the design of security schemes, we investigate how to solve the eavesdropping, modification and one particular type of relay attacks toward the tag-to-reader communication in passive RFID systems without requiring lightweight ciphers. To this end, we propose a novel physical layer scheme, called Backscatter modulation- and Uncoordinated frequency hopping-assisted Physical Layer Enhancement (BUPLE). The idea behind it is to use the amplitude of the carrier to transmit messages as normal, while to utilize its periodically varied frequency to hide the transmission from the eavesdropper/relayer and to exploit a random sequence modulated to the carrier's phase to defeat malicious modifications. We further improve its eavesdropping resistance through the coding in the physical layer, since BUPLE ensures that the tag-to-eavesdropper channel is strictly noisier than the tag-to-reader channel. Three practical Wiretap Channel Codes (WCCs) for passive tags are then proposed: two of them are constructed from linear error correcting codes, and the other one is constructed from a resilient vector Boolean function. The security and usability of BUPLE in conjunction with WCCs are further confirmed by our proof-of-concept implementation and testing. Eavesdropping the communication between a legitimate reader and a victim tag to obtain raw data is a basic tool for the adversary. However, given the fundamentality of eavesdropping attacks, there are limited prior work investigating its intension and extension for passive RFID systems. To this end, we firstly identified a brand-new attack, working at physical layer, against backscattered RFID communications, called unidirectional active eavesdropping, which defeats the customary impression that eavesdropping is a ``passive" attack. To launch this attack, the adversary transmits an un-modulated carrier (called blank carrier) at a certain frequency while a valid reader and a tag interacts at another frequency channel. Once the tag modulates the amplitude of reader's signal, it causes fluctuations on the blank carrier as well. By carefully examining the amplitude of the backscattered versions of the blank carrier and the reader's carrier, the adversary could intercept the ongoing reader-tag communication with either significantly lower bit error rate or from a significantly greater distance away. Our concept is demonstrated and empirically analyzed towards a popular low-cost RFID system, i.e., EPC Gen2. Although active eavesdropping in general is not trivial to be prohibited, for a particular type of active eavesdropper, namely a greedy proactive eavesdropper, we propose a simple countermeasure without introducing extra cost to current RFID systems. The needs of cryptographic primitives on constraint devices keep increasing with the growing pervasiveness of these devices. One recent design of the lightweight block cipher is Hummingbird-2. We study its cryptographic strength under a novel technique we developed, called Differential Sequence Attack (DSA), and present the first cryptanalytic result on this cipher. In particular, our full attack can be divided into two phases: preparation phase and key recovery phase. During the key recovery phase, we exploit the fact that the differential sequence for the last round of Hummingbird-2 can be retrieved by querying the full cipher, due to which, the search space of the secret key can be significantly reduced. Thus, by attacking the encryption (decryption resp.) of Hummingbird-2, our algorithm recovers 36-bit (another 28-bit resp.) out of 128-bit key with $2^{68}$ ($2^{60}$ resp.) time complexity if particular differential conditions of the internal states and of the keys at one round can be imposed. Additionally, the rest 64-bit of the key can be exhaustively searched and the overall time complexity is dominated by $2^{68}$. During the preparation phase, by investing $2^{81}$ effort in time, the adversary is able to create the differential conditions required in the key recovery phase with at least 0.5 probability. As an additional effort, we examine the cryptanalytic strength of another lightweight candidate known as A2U2, which is the most lightweight cryptographic primitive proposed so far for low-cost tags. Our chosen-plaintext-attack fully breaks this cipher by recovering its secret key with only querying the encryption twice on the victim tag and solving 32 sparse systems of linear equations (where each system has 56 unknowns and around 28 unknowns can be directly obtained without computation) in the worst case, which takes around 0.16 second on a Thinkpad T410 laptop

ENERGY-EFFICIENT AND SECURE HARDWARE FOR INTERNET OF THINGS (IoT) DEVICES

Internet of Things (IoT) is a network of devices that are connected through the Internet to exchange the data for intelligent applications. Though IoT devices provide several advantages to improve the quality of life, they also present challenges related to security. The security issues related to IoT devices include leakage of information through Differential Power Analysis (DPA) based side channel attacks, authentication, piracy, etc. DPA is a type of side-channel attack where the attacker monitors the power consumption of the device to guess the secret key stored in it. There are several countermeasures to overcome DPA attacks. However, most of the existing countermeasures consume high power which makes them not suitable to implement in power constraint devices. IoT devices are battery operated, hence it is important to investigate the methods to design energy-efficient and secure IoT devices not susceptible to DPA attacks. In this research, we have explored the usefulness of a novel computing platform called adiabatic logic, low-leakage FinFET devices and Magnetic Tunnel Junction (MTJ) Logic-in-Memory (LiM) architecture to design energy-efficient and DPA secure hardware. Further, we have also explored the usefulness of adiabatic logic in the design of energy-efficient and reliable Physically Unclonable Function (PUF) circuits to overcome the authentication and piracy issues in IoT devices. Adiabatic logic is a low-power circuit design technique to design energy-efficient hardware. Adiabatic logic has reduced dynamic switching energy loss due to the recycling of charge to the power clock. As the first contribution of this dissertation, we have proposed a novel DPA-resistant adiabatic logic family called Energy-Efficient Secure Positive Feedback Adiabatic Logic (EE-SPFAL). EE-SPFAL based circuits are energy-efficient compared to the conventional CMOS based design because of recycling the charge after every clock cycle. Further, EE-SPFAL based circuits consume uniform power irrespective of input data transition which makes them resilience against DPA attacks. Scaling of CMOS transistors have served the industry for more than 50 years in providing integrated circuits that are denser, and cheaper along with its high performance, and low power. However, scaling of the transistors leads to increase in leakage current. Increase in leakage current reduces the energy-efficiency of the computing circuits,and increases their vulnerability to DPA attack. Hence, it is important to investigate the crypto circuits in low leakage devices such as FinFET to make them energy-efficient and DPA resistant. In this dissertation, we have proposed a novel FinFET based Secure Adiabatic Logic (FinSAL) family. FinSAL based designs utilize the low-leakage FinFET device along with adiabatic logic principles to improve energy-efficiency along with its resistance against DPA attack. Recently, Magnetic Tunnel Junction (MTJ)/CMOS based Logic-in-Memory (LiM) circuits have been explored to design low-power non-volatile hardware. Some of the advantages of MTJ device include non-volatility, near-zero leakage power, high integration density and easy compatibility with CMOS devices. However, the differences in power consumption between the switching of MTJ devices increase the vulnerability of Differential Power Analysis (DPA) based side-channel attack. Further, the MTJ/CMOS hybrid logic circuits which require frequent switching of MTJs are not very energy-efficient due to the significant energy required to switch the MTJ devices. In the third contribution of this dissertation, we have investigated a novel approach of building cryptographic hardware in MTJ/CMOS circuits using Look-Up Table (LUT) based method where the data stored in MTJs are constant during the entire encryption/decryption operation. Currently, high supply voltage is required in both writing and sensing operations of hybrid MTJ/CMOS based LiM circuits which consumes a considerable amount of energy. In order to meet the power budget in low-power devices, it is important to investigate the novel design techniques to design ultra-low-power MTJ/CMOS circuits. In the fourth contribution of this dissertation, we have proposed a novel energy-efficient Secure MTJ/CMOS Logic (SMCL) family. The proposed SMCL logic family consumes uniform power irrespective of data transition in MTJ and more energy-efficient compared to the state-of-art MTJ/ CMOS designs by using charge sharing technique. The other important contribution of this dissertation is the design of reliable Physical Unclonable Function (PUF). Physically Unclonable Function (PUF) are circuits which are used to generate secret keys to avoid the piracy and device authentication problems. However, existing PUFs consume high power and they suffer from the problem of generating unreliable bits. This dissertation have addressed this issue in PUFs by designing a novel adiabatic logic based PUF. The time ramp voltages in adiabatic PUF is utilized to improve the reliability of the PUF along with its energy-efficiency. Reliability of the adiabatic logic based PUF proposed in this dissertation is tested through simulation based temperature variations and supply voltage variations

Security of Ubiquitous Computing Systems

The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license

Novel Cryptographic Authentication Mechanisms for Supply Chains and OpenStack

In this dissertation, first, we studied the Radio-Frequency Identification (RFID) tag authentication problem in supply chains. RFID tags have been widely used as a low-cost wireless method for detecting counterfeit product injection in supply chains. We open a new direction toward solving this problem by using the Non-Volatile Memory (NVM) of recent RFID tags. We propose a method based on this direction that significantly improves the availability of the system and costs less. In our method, we introduce the notion of Software Unclonability, which is a kind of one-time MAC for authenticating random inputs. Also, we introduce three lightweight constructions that are software unclonable. Second, we focus on OpenStack that is a prestigious open-source cloud platform. OpenStack takes advantage of some tokening mechanisms to establish trust between its modules and users. It turns out that when an adversary captures user tokens by exploiting a bug in a module, he gets extreme power on behalf of users. Here, we propose a novel tokening mechanism that ties commands to tokens and enables OpenStack to support short life tokens while it keeps the performance up

Efficient and Secure Implementations of Lightweight Symmetric Cryptographic Primitives

This thesis is devoted to efficient and secure implementations of lightweight symmetric cryptographic primitives for resource-constrained devices such as wireless sensors and actuators that are typically deployed in remote locations. In this setting, cryptographic algorithms must consume few computational resources and withstand a large variety of attacks, including side-channel attacks. The first part of this thesis is concerned with efficient software implementations of lightweight symmetric algorithms on 8, 16, and 32-bit microcontrollers. A first contribution of this part is the development of FELICS, an open-source benchmarking framework that facilitates the extraction of comparative performance figures from implementations of lightweight ciphers. Using FELICS, we conducted a fair evaluation of the implementation properties of 19 lightweight block ciphers in the context of two different usage scenarios, which are representatives for common security services in the Internet of Things (IoT). This study gives new insights into the link between the structure of a cryptographic algorithm and the performance it can achieve on embedded microcontrollers. Then, we present the SPARX family of lightweight ciphers and describe the impact of software efficiency in the process of shaping three instances of the family. Finally, we evaluate the cost of the main building blocks of symmetric algorithms to determine which are the most efficient ones. The contributions of this part are particularly valuable for designers of lightweight ciphers, software and security engineers, as well as standardization organizations. In the second part of this work, we focus on side-channel attacks that exploit the power consumption or the electromagnetic emanations of embedded devices executing unprotected implementations of lightweight algorithms. First, we evaluate different selection functions in the context of Correlation Power Analysis (CPA) to infer which operations are easy to attack. Second, we show that most implementations of the AES present in popular open-source cryptographic libraries are vulnerable to side-channel attacks such as CPA, even in a network protocol scenario where the attacker has limited control of the input. Moreover, we describe an optimal algorithm for recovery of the master key using CPA attacks. Third, we perform the first electromagnetic vulnerability analysis of Thread, a networking stack designed to facilitate secure communication between IoT devices. The third part of this thesis lies in the area of side-channel countermeasures against power and electromagnetic analysis attacks. We study efficient and secure expressions that compute simple bitwise functions on Boolean shares. To this end, we describe an algorithm for efficient search of expressions that have an optimal cost in number of elementary operations. Then, we introduce optimal expressions for first-order Boolean masking of bitwise AND and OR operations. Finally, we analyze the performance of three lightweight block ciphers protected using the optimal expressions