The broadcast nature of wireless medium has made information security as one of the most important and critical issues in wireless systems. Physical layer security, which is based on information-theoretic secrecy concepts, can be used to secure the wireless channels by exploiting the noisiness and imperfections of the channels. Massive multiple-input multiple-output (MIMO) systems, which are equipped with very large antenna arrays at the base stations, have a great potential to boost the physical layer security by generating the artificial noise (AN) with the exploitation of excess degrees-of-freedom available at the base stations. In this thesis, we investigate physical layer security provisions in the presence of passive/active eavesdroppers for single-hop massive MIMO, dual-hop relay-assisted massive MIMO and underlay spectrum-sharing massive MIMO systems. The performance of the proposed security provisions is investigated by deriving the achievable rates at the user nodes, the information rate leaked into the eavesdroppers, and the achievable secrecy rates. Moreover, the effects of active pilot contamination attacks, imperfect channel state information (CSI) acquisition at the base-stations, and the availability of statistical CSI at the user nodes are quantified. The secrecy rate/performance gap between two AN precoders, namely the random AN precoder and the null-space based AN precoder, is investigated. The performance of hybrid analog/digital precoding is compared with the full-dimensional digital precoding. Furthermore, the physical layer security breaches in underlay spectrum-sharing massive MIMO systems are investigated, and thereby, security provisions are designed/analyzed against active pilot contamination attacks during the channel estimation phase. A power-ratio based active pilot attack detection scheme is investigated, and thereby, the probability of detection is derived. Thereby, the vulnerability of uplink channel estimation based on the pilots transmitted by the user nodes in time division duplexing based massive MIMO systems is revealed, and the fundamental trade-offs among physical layer security provisions, implementation complexity and performance gains are discussed.

This thesis deals with smart home issue, analyzes existing solutions and is focused on the system that is developed in collaboration with FIT VUT in Brno. The emphasis is on the description of client application for control and monitoring of smart home system. Furthermore, the work discussed base theoretical knowledge from internet communication field, which is closely related to these issues. The core of the work is to design a communication protocol between the server and a mobile device. Finally, the work also includes a description of a network layer at the device using this protocol. The last part is devoted to testing and evaluation of the final solution.

To securely communicate information between parties or locations is not an easy task considering the possible attacks or unintentional changes that can occur during communication. Encryption is often used to protect secret information from unauthorised access. Encryption, however, is not inconspicuous and the observable exchange of encrypted information between two parties can provide a potential attacker with information on the sender and receiver(s). The presence of encrypted information can also entice a potential attacker to launch an attack on the secure communication. This dissertation investigates and discusses the use of image steganography, a technology for hiding information in other information, to facilitate secure communication. Secure communication is divided into three categories: self-communication, one-to-one communication and one-to-many communication, depending on the number of receivers. In this dissertation, applications that make use of image steganography are implemented for each of the secure communication categories. For self-communication, image steganography is used to hide one-time passwords (OTPs) in images that are stored on a mobile device. For one-to-one communication, a decryptor program that forms part of an encryption protocol is embedded in an image using image steganography and for one-to-many communication, a secret message is divided into pieces and different pieces are embedded in different images. The image steganography applications for each of the secure communication categories are discussed along with the advantages and disadvantages that the applications have over more conventional secure communication technologies. An additional image steganography application is proposed that determines whether information is modified during communication. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Computer Science / unrestricted

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<p><strong>OBJECTIVE: </strong>The aim of this study was to explore an alternative method of secure data exchange of patient information among physicians using their existing email.<strong></strong></p> <p><strong>METHODS: </strong>A four-step framework was designed to effectively conduct the research. It involved designing a prototype of a web-based system called ST-SecRx to simulate secure communication between physicians while exchanging sensitive patient data through email. The simulation achieved through the system was meant to determine and measure response of physicians to the use of secure email or similar communication tools for exchanging patient data. Physicians were invited to use ST-SecRx and subsequently participate in a survey to determine its acceptability and their perceptions about the usefulness of the software. Finally, the data collected from the survey were analyzed.</p> <p><strong>RESULTS:</strong> Data were collected from 22 physicians from various healthcare facilities in the province of Ontario, Canada. Eliminating questionnaires with no response resulted in 19 valid responses. Results revealed that 57.9% used email support provided by their organization for exchanging patient data. Over 70% acknowledged that factors such as: ease of use, not having to use an email different from the one provided by their employer, not having to create and remember new password every three to six months, and data transfer complying with privacy regulations would facilitate their use of ST-SecRx. More than 50% of the physicians felt that the simulated system as demonstrated to them was more secure and easier to use when compared to previously used methods of patient data exchange through email. The majority of the physicians (from 57.9% to 73.7%) agreed with all the six questions on behavioral intention to use ST-SecRx. Overall 42% were willing to pay between $5 and $20 per month for ST-SecRx. Additional analysis of data by age, sex and discipline did not reveal any substantial differences in their enthusiasm to use the system.</p> <p><strong>CONCLUSION: </strong>The current research was successful providing data on what is important to clinicians who want to exchange data on patients with other clinicians. Use of systems similar to the prototype ST-SecRx could be an improvement over conventional email, provided that they would ensure security using encrypted technology under public key infrastructure methods and systems. Overall the physicians were satisfied with ST-SexRx and found it simple, fast, easy to use, and secure, and they indicated that they intended to use it if it were made available and it conformed to privacy and security standards. Also, such a secure system would have the potential to reduce the overall cost of healthcare by reducing duplication of diagnostic tests and making patient- specific information exchange faster. More research needs to be conducted with a larger sample size to validate the findings of this study. The limitations, dissatisfaction, and concerns expressed by the physicians who used ST-SecRx could direct future research. Future studies could include other healthcare professionals in the exchange of sensitive clinical data.</p> / Master of Science (MSc)

This thesis considers a communication system with chaotic modulation. Noise-like signals are generated by chaotic systems with different parameters to modulate binary digital signals. Demodulation is performed by both the Extended Kalman Filter (EKF) and Optimum Decoding Based Smoothing Algorithm (ODSA). Simulations are performed using both of these algorithms for different parameters affecting the performance of the communication system. Simulation results of these algorithms are compared.

Internet of Things (IoT) is a concept that encompasses various objects and methods of communication to exchange information. Today IoT is more a descriptive term of a vision that everything should be connected to the internet. IoT will be fundamental in the future because the concept opens up opportunities for new services and new innovations. All objects will be connected and able to communicate with each other, while they operate in unprotected environments. This later aspect leads to major security challenges. Today, IoT is in great need of standardization and clear architectures that describe how this technology should be implemented and how IoT devices interact with each other in a secure manner. The security challenges are rooted in the technology and how information is acquired and manipulated by this technology. This thesis provides an introduction to what the IoT is and how it can be used as well as some of the threats that IoT may face in regards to information security. In addition, the thesis provides the reader with some suggestions about how to potentially solve the fundamental need for authentication and secure communications. The solutions presented are based on both contemporary solutions and technologies that are under development for the future. Contemporary solutions are based on security protocols such as IPSec and DTLS. These protocols are being used in an environment that extends across the Internet and into a 6LoWPAN network. The proposed authentication solution has been developed based on a public key infrastructure and trust models for certificate management. As future work, the thesis presents several research areas where this thesis can be used as a basis. These specialization areas include further analysis of vulnerabilities and an implementation of the proposed solutions. / Internet of Things (IoT) är ett koncept som omfattar olika objekt och kommunikationsmetoder för utbyte av information. Idag är IoT mer en beskrivande term av den framtidsvision som finns att allting ska vara uppkopplat på internet. IoT kommer vara fundamentalt i framtiden eftersom konceptet öppnar upp möjligheter för nya tjänster samt nya innovationer. Då alla objekt ska vara uppkopplade och kunna kommunicera med varandra samtidigt som de skall kunna operera i oskyddade miljöer, bidrar detta till stora säkerhetsutmaningar. Dagens IoT är i stort behov av standardisering och klara strukturer för hur tekniken ska implementeras samt samverka med varandra på ett säkert sätt.  Utmaningarna ligger i att säkra tekniken samt informationen som tekinken bidrar med. Denna rapport ger en introduktion till vad IoT är och hur det kan användas samt vilka hot som IoT kan möta i avseende till informationssäkerhet. Utöver detta så förser rapporten läsaren med förslag om hur man eventuellt kan lösa de fundamentala behoven av autentisering och säker kommunikation. Lösningarna som läggs fram är baserade på både nutida lösningar och teknik som är under utveckling inför framtiden. Nutida lösningar är baserade på säkerhetsprotokoll som IPsec och DTLS som används i en miljö som sträcker över internet och in i ett 6LoWPAN nätverk. Den autentiseringslösning som tagits fram grundar sig på PKI och förtroendemodeller för certifikathantering. För framtida arbete presenteras flertalet vidare fördjupningsområden där denna rapport kan användas som grund. Dessa fördjupningsområden inkluderar vidare analys av sårbarheter och implementation av de lösningar som tagits fram.

Vehicle-to-vehicle communication (V2V) has become one of the most risingtechnologies in recent years, and due to the implementation of 5G different solutionshave begun to be designed that allow communication between vehiclesand pedestrians (V2P). V2P communication is a challenge for two reasons:the incompatibility of technologies, as well as the need to have a real-timecommunication (crucial when sending and receiving road hazard messages).This document presents a solution for pedestrian-to-vehicle communication,detecting pedestrian risk situations using the mobile phone sensors and messagesby the vehicles. An architecture and communication protocol is presented,to send warning messages with low delay in a secure and private waywithout harming efficiency. Two algorithms are used, one implemented in anAndroid application and another one in a server, with the purpose of detectingpedestrian misbehavior in the road and reducing the amount of direct messagesbetween the nodes of the system. / Kommunikation mellan fordonen (V2V) har blivit en av de mest stigande teknikernaunder de senaste åren, och på grund av implementeringen av 5G harolika lösningar börjat utformas som möjliggör kommunikation mellan fordonoch fotgängare (V2P). V2P-kommunikation är en utmaning av två skäl: teknikensinkompatibilitet, liksom behovet av att ha en kommunikation i realtid(avgörande när du skickar och tar emot meddelanden om vägfara). Detta dokumentpresenterar en lösning för kommunikation mellan fotgängare och fordon,från upptäckten av fotgängarsrisksituationer på vägen använder mobiltelefonsensorertill fordonen mottagande meddelanden. Ett fullständigt arkitekturochkommunikationsprotokoll presenteras för att skicka flera varningsmeddelandenmed minsta möjliga fördröjning och på ett säkert och privat sätt, utan attförlora systemets effektivitet. Dessutom används två algoritmer, en implementeradi en Android-applikation och en annan på en server, i syfte att upptäckauppförande av fotgängare på vägen och minska mängden direktmeddelandenmellan systemets noder.

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This dissertation investigates the application of computational intelligence methods in the analysis of nonlinear chaotic systems in the framework of many known and newly designed complex systems. Parallel comparisons are made between these methods. This provides insight into the difficult challenges facing nonlinear systems characterization and aids in developing a generalized algorithm in computing algorithmic complexity measures, Lyapunov exponents, information dimension and topological entropy. These metrics are implemented to characterize the dynamic patterns of discrete and continuous systems. These metrics make it possible to distinguish order from disorder in these systems. Steps required for computing Lyapunov exponents with a reorthonormalization method and a group theory approach are formalized. Procedures for implementing computational algorithms are designed and numerical results for each system are presented. The advance-time sampling technique is designed to overcome the scarcity of phase space samples and the buffer overflow problem in algorithmic complexity measure estimation in slow dynamics feedback-controlled systems. It is proved analytically and tested numerically that for a quasiperiodic system like a Fibonacci map, complexity grows logarithmically with the evolutionary length of the data block. It is concluded that a normalized algorithmic complexity measure can be used as a system classifier. This quantity turns out to be one for random sequences and a non-zero value less than one for chaotic sequences. For periodic and quasi-periodic responses, as data strings grow their normalized complexity approaches zero, while a faster deceasing rate is observed for periodic responses. Algorithmic complexity analysis is performed on a class of certain rate convolutional encoders. The degree of diffusion in random-like patterns is measured. Simulation evidence indicates that algorithmic complexity associated with a particular class of 1/n-rate code increases with the increase of the encoder constraint length. This occurs in parallel with the increase of error correcting capacity of the decoder. Comparing groups of rate-1/n convolutional encoders, it is observed that as the encoder rate decreases from 1/2 to 1/7, the encoded data sequence manifests smaller algorithmic complexity with a larger free distance value.