A wireless sensor network is a collection of numerous sensors distributed on an area of interest to collect and process data from the environment. One particular threat in wireless sensor networks is node compromise attacks, that is, attacks where the adversary gets physical access to a node and to the programs and keying material stored on it. Only authorized queries should be allowed in the network and the integrity and confidentiality of the data that is being collected should be protected. We propose a layered key distribution scheme together with two protocols for query authentication and confidential data aggregation. The layered key distribution is more robust to node and communication failures than a predefined tree structure. The protocols are secure under the assumption that less than n sensor nodes are compromised. n is a design parameter that allows us to trade off security for overhead. When more than n sensor nodes are compromised, our simulations show that the attacker can only introduce unauthorized queries into a limited part of the network and can only get access to a small part of the data that is aggregated in the network. Considering the data collection protocol we also contribute with strategies to reduce the energy consumption of an integrity preserving in-network aggregation scheme to a level below the energy consumption of a non-aggregation scheme. Our improvements reduce node congestion by a factor of three and the total communication load by 30%. Location privacy of the users carrying mobile devices is another aspect considered in this thesis. Considering a mobile sink that collects data from the network, we propose a strategy for data collection that requires no information about the location and movement pattern of the sink. We show that it is possible to provide data collection services, while protecting the location privacy of the sink. When mobile phones with built-in sensors are used as sensor nodes, location information about where the data has been sensed can be used to trace users and infer other personal information about them, like state of health or personal preferences. Therefore, location privacy preserving mechanisms have been proposed to provide location privacy to the users. We investigate how a location privacy preserving mechanism influences the quality of the collected data and consider strategies to reconstruct the data distribution without compromising location privacy. / WISENET

This thesis encompasses a collection of four pieces of work on wave-particle duality, weak-value-assisted tomography, high-dimensional quantum key distribution, and phase-only holograms. In the work on duality, we derive a novel duality relation, and we sketch a thought experiment that leads to an apparent violation of the duality principle. In the project on tomography, we perform a state determination procedure with weak values, and we study the accuracy of the method. In the quantum cryptography project, we optimize an experimental implementation of a quantum cryptography system where two parties share information with the orbital angular momentum degree of freedom of entangled photon pairs. Finally, in the work on holography, we establish the exact solution to the encryption of a phase-only hologram, and experimentally demonstrate its application to spatial light modulators. The four projects provide improvements on measurement procedures in applied and fundamental quantum mechanics.

Quantum communication promises to outperform its classical counterparts and enable protocols previously impossible. Specifically, quantum key distribution (QKD) allows a cryptographic key to be shared between distant parties with provable security. Much work has been performed on theoretical and experi- mental aspects of QKD, and the push is on to make it commercially viable and integrable with existing technologies. To this end I have performed simulations and experiments on QKD and other quantum protocols in regimes previously unexplored. The first experiment involves QKD via distributed entanglement through the standard telecommunications optical fibre network. I show that entanglement is preserved, even when the photons used are a shorter wavelength than the design of the optical fibre calls for. This surprising result is then used to demonstrate QKD over installed optical fibre, even with co-propagating classical traffic. Because the quantum and classical signals are sufficiently separated in wavelength, little cross-talk is observed, leading to high compatibility between this type of QKD and existing telecommunications infrastructure. Secondly, I demonstrate the key components of fully-modulated decoy-state QKD over the highest-loss channel to date, using a novel photon source based on weak coherent (laser) pulses. This system has application in a satellite uplink of QKD, which would enable worldwide secure communication. The uplink allows the complex quantum source to be kept on the ground while only simple receivers are in space, but suffers from high link loss due to atmospheric turbulence, necessitating the use of specific photon detectors and highly tailored photon pulses. My results could be applied in a near term satellite mission.

In the age of information explosion, there is huge amount of information generated every second. Some of the information generated, for example news, is supposed to be shared by public and anyone in the world can get a copy of it. However, sometimes, information is only supposed to be maintain private or only shared by a given group of people. In the latter case, information protection becomes very important. There are various ways to protect information. One of the technical ways is cryptography, which is an area of interest for mathematicians, computer scientists and physicists. As a new area in cryptography, physical layer security has been paid great attention recently. Quantum key distribution is a hot research topic for physical layer security in the two decades. This thesis focuses on two quantum key distribution protocols that can potentially increase the key generation rate and lower the cost. On protocol is based on amplified spontaneous emission as signal source and the other one is based on discretely signaled continuous variable quantum communication. The security analysis and experimental implementation issues for both protocols are discussed.

[pt] As comunicações quânticas estão rapidamente integrando-se às redes de fibras ópticas, entretanto muitos desafios de engenharia ainda existem para essa aglutinação. Esta tese discute algumas soluções práticas para a melhoria de aplicações reais em comunicações quânticas em fibras ópticas. No primeiro experimento uma fonte de pares de fótons emaranhados não-degenerados, de banda-estreita, empregando conversão espontânea paramétrica descendente (CEPD) é utilizada para demonstrar a viabilidade da distribuição quântica de chaves (DQC) através de 27 km de fibras ópticas, com o canal de sincronismo presente na mesma fibra com uma separação de 0.8 nm em comprimento de onda. A outra demonstração utilizou uma fonte heráldica de fótons únicos também baseada em CEPD para a realização de DQC através de 25 km de fibras ópticas com a utilização do protocolo de decoy states pela primeira vez. Houve também um estudo dos impactos gerados por ruído Raman espontâneo causado por um canal óptico clássico presente na mesma fibra que o canal quântico. Um protocolo para gerar números verdadeiramente aleatórios em um sistema de DQC independente da taxa de transmissão do sistema é proposto, e um experimento prova-de-princípio demonstra a idéia. Finalmente um sistema de controle automático de polarização é utilizado para a realização de uma sessão de DQC através de 16 km de fibras ópticas utilizando codificação em polarização, mesmo sob a presença de um embaralhador rápido do estado de polarização. / [en] Quantum communications is quickly becoming integrated within fiber optical networks and still many engineering challenges remain towards this interweaving. This thesis deals with some practical solutions toward improving real-world applications in quantum communications within optical fibers. In the first experiment, a non-degenerate narrowband entangled pair single-photon source based on spontaneous parametric down-conversion (SPDC) is used to show the feasibility of performing quantum key distribution (QKD) through 27 km of optical fiber, with the synchronization channel wavelength multiplexed in the same fiber with a channel spacing of just 0.8 nm. A second experiment uses a heralded single-photon source also based on SPDC to perform QKD over 25 km of optical fiber with the decoy state modification for the first time. Then there is a study of the problems caused by spontaneous Raman induced noise due to the presence of a classical signal in the same fiber as the quantum channel. A protocol to generate truly random numbers in a QKD setup independent of the system s transmission rate is proposed, and a proof-of-principle experiment demonstrates the idea. Finally an automatic polarization control system is used to perform a QKD session over 16 km of optical fiber using polarization encoding, even in the presence of a fast polarization scrambler.

[pt] A criptografia quântica se apresenta como uma área relativamente nova e interdisciplinar que, fundamentada nas leis da mecânica quântica, promete solucionar o grande desafio da criptografia simétrica clássica atual, a distribuição de chaves. A distribuição quântica de chaves provê comunicação absolutamente segura entre duas partes, possibilitando o compartilhamento de um segredo, que será utilizado na posterior encriptação da mensagem. Esta dissertação relata a implementação física experimental de um sistema óptico de distribuição quântica de chaves com codificação em freqüência por dupla-modulação em amplitude e fase e sincronização por multiplexação no domínio do comprimento de onda. São introduzidos os conceitos teóricos básicos necessários ao desenvolvimento do tema e apresentadas medições de caracterização dos principais componentes do sistema, bem como resultados de medidas sistêmicas clássicas e quânticas. / [en] The quantum cryptography rises as a relatively new and interdisciplinary area that, grounded in the quantum mechanics laws, promises to solve the major challenge in the actual symmetric classical cryptography, the key distribution. The quantum key distribution enables absolutely secure communication between two parts, making them able to share a secret that will be used in the posterior message encryptation. This dissertation reports the experimental physical implementation of an optical quantum key distribution system with frequency coding by amplitude and phase double-modulation process and wavelengthdivision multiplexing synchronization. The mean theoretical foundations are briefly introduced and the characterization measurements of the most important devices are shown, as like results from systemic classical and quantum measurements.

The thesis presents the basics of Quantum Key Distribution, a survey of the present techniques, a look at the possible future, and finally a comparison to the alternative technique of using public key or manual distribution of keys. Techniques to integrate QKD with the existing telecom fiber infrastructure have been studied, and so has the EU-funded project SECOQC. Last the security and efficiency of QKD have been examined, with focus on what level of security that is required, existing security solutions have been used as a comparison. / ICG QC

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-01-14T13:44:23Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Mário Teixeira Lemes - 2014.pdf: 980494 bytes, checksum: f983125ef07bccd0b90e2d6ac45a5d1e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-01-14T13:45:38Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Mário Teixeira Lemes - 2014.pdf: 980494 bytes, checksum: f983125ef07bccd0b90e2d6ac45a5d1e (MD5) / Made available in DSpace on 2015-01-14T13:45:38Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Mário Teixeira Lemes - 2014.pdf: 980494 bytes, checksum: f983125ef07bccd0b90e2d6ac45a5d1e (MD5) Previous issue date: 2014-02-21 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Key distribution schemes are commonly used to leverage security properties in Wireless Sensor Networks (WSN). No key distribution scheme is coupled to the link layer architecture TinySec, which significantly compromises their security level. The goal of this work is propose a new approach of identity-based key distribution to be used in conjunction with the framework TinySec, solving the weakness of this architecture that is based on a key establishment scheme very simple: the sharing of a same key before the deployment. The identity based key agreement to be use together with TinySec causes the damage from attacks become local and allows that a sensor node send encrypted information to another node the not yet calculated the secret key. The junction results in a protocol with high level of security and is suitable to critical applications of WSN, such as the military or in health. / Os esquemas de distribuição de chaves criptográficas comumente são utilizados para alavancar propriedades de segurança em Redes de Sensores Sem Fio (RSSF). Nenhum mecanismo de distribuição de chaves é atrelado a arquitetura da camada de enlace TinySec, o que compromete consideravelmente o seu nível de segurança. O objetivo deste trabalho é propor uma abordagem de distribuição de chaves baseada em identidade para ser utilizada em conjunto com o framework TinySec, solucionando a fragilidade desta arquitetura de segurança por se basear em um esquema de estabelecimento de chaves muito simples: o compartilhamento de uma mesma chave criptográfica antes da fase de implantação. Este esquema de distribuição de chaves baseado em identidade utilizado em conjunto com o framework TinySec faz com que os danos ocasionados por ataques se tornem estritamente locais e permite que um nó sensor envie informações encriptadas para outro nó que ainda não tenha calculado o segredo criptográfico. A junção resulta em um protocolo com um maior nível de segurança sendo indicado para aplicações críticas que fazem uso das RSSF, tais como na área militar ou na área da saúde.

We experimentally demonstrate an eight-state continuous-variable quantum key distribution (CV-QKD) over atmospheric turbulence channels. The high secret key rate (SKR) is enabled by 4-D multiplexing of 96 channels, i.e., six-channel wavelength-division multiplexing, four-channel orbital angular momentum multiplexing, two-channel polarization multiplexing, and two-channel spatial-position multiplexing. The atmospheric turbulence channel is emulated by a spatial light modulator on which a series of azimuthal phase patterns yielding Andrews' spectrum are recorded. A commercial coherent receiver is implemented at Bob's side, followed by a phase noise cancellation stage, where channel transmittance can be monitored accurately and phase noise can be effectively eliminated. Compared to four-state CV-QKD, eight-state CV-QKD protocol potentially provides a better performance by offering higher SKR, better excess noise tolerance, and longer secure transmission distance. In our proposed CV-QKD system, the minimum transmittances of 0.24 and 0.26 are required for OAM states of 2 (or -2) and 6 (or -6), respectively, to guarantee the secure transmission. A maximum SKR of 3.744 Gb/s is experimentally achievable, while a total SKR of 960 Mb/s can be obtained in case of mean channel transmittances.

When using quantum key distribution (QKD), one of the trade-offs for security is that the generation rate of a secret key is typically very low. Recent works have shown that using a weak coherent source allows for higher secret key generation rates compared to an entangled photon source, when a channel with low loss is considered. In most cases, the system that is being studied is over a fiber-optic communication channel. Here a theoretical QKD system using the BB92 protocol and entangled photons over a free-space maritime channel with multiple spatial modes is presented. The entangled photons are generated from a spontaneous parametric down conversion (SPDC) source of type II. To employ multiple spatial modes, the transmit apparatus will contain multiple SPDC sources, all driven by the pump lasers assumed to have the same intensity. The receive apparatuses will contain avalanche photo diodes (APD), modeled based on the NuCrypt CPDS-1000 detector, and located at the focal point of the receive aperture lens. The transmitter is assumed to be located at Alice and Bob will be located 30 km away, implying no channel crosstalk will be introduced in the measurements at Alices side due to turbulence. To help mitigate the effects of atmospheric turbulence, adaptive optics will be considered at the transmitter and the receiver. An eavesdropper, Eve, is located 15 km from Alice and has no control over the devices at Alice or Bob. Eve is performing the intercept resend attack and listening to the communication over the public channel. Additionally, it is assumed that Eve can correct any aberrations caused by the atmospheric turbulence to determine which source the photon was transmitted from. One, four and nine spatial modes are considered with and without applying adaptive optics and compared to one another.