The fast development of wireless networks, which are intrinsically exposed to eavesdropping, has created a growing concern for confidentiality. While classical cryptographic schemes require a key provided by the end-user, physical-layer security leverages the randomness of the physical communication medium as a source of secrecy. The main benefit of physical-layer security techniques is their relatively low cost and their ability to combine with any existing security mechanisms. This dissertation provides an analysis including the theoretical study of the two-way wiretap channel to obtain a better insight into how to design coding mechanisms, practical tests with experimental systems, and the design of actual codes. From a theoretical standpoint, the study confirms the benefits of combining several multi-user coding techniques including cooperative jamming, coded cooperative jamming and secret key generation. For these different mechanisms, the trade-off between reliability, secrecy and communication rate is clarified under a stringent strong secrecy metric. Regarding the design of practical codes, spatially coupled LDPC codes, which were originally designed for reliability, are modified to develop a coded cooperative jamming code. Finally, a proof-of-principle practical wireless system is provided to show how to implement a secret key generation system on experimental programmable radios. This testbed is then used to assess the realistic performance of such systems in terms of reliability, secrecy and rate.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2014-09-16T12:52:36Z No. of bitstreams: 2 Dissertação EnioPerez.pdf: 2190954 bytes, checksum: 8abd6c2cd31279e28971c632f6ed378b (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-09-16T14:10:30Z (GMT) No. of bitstreams: 2 Dissertação EnioPerez.pdf: 2190954 bytes, checksum: 8abd6c2cd31279e28971c632f6ed378b (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-16T14:10:30Z (GMT). No. of bitstreams: 2 Dissertação EnioPerez.pdf: 2190954 bytes, checksum: 8abd6c2cd31279e28971c632f6ed378b (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2011-08-26 / Intuitively, the basic idea of Design Theory consists of a way to select subsets, also called blocks, of a finite set, so that some properties are satisfied. The more general case are the blocks designs. A PBD is an ordered pair (S;B), where S is a finite set of symbols, and B is a collection of subsets of S called blocks, such that each pair of distinct elements of S occur together in exactly one block of B. A Steiner Triple System is a particular case of a PBD, where every block has size only 3, being called triples. The main focus is in building technology systems. By resolvability is discussed as a Steiner Triple Systems is resolvable, and when it is not resolvable. This theory has several applications, eg, embeddings and even problems related to computational complexity. / Intuitivamente, a idéia básica de um Planejamento Combinatório consiste em uma maneira de selecionar subconjuntos, também chamados de blocos, de um conjunto finito, de modo que algumas propriedades especificadas sejam satisfeitas. O caso mais geral são os planejamentos balanceados. Um PBD é um par ordenado (S;B), onde S é um conjunto finito de símbolos, e B é uma coleção de subconjuntos de S chamados blocos, tais que cada par de elementos distintos de S ocorrem juntos em exatamente um bloco de B. Um Sistema Triplo de Steiner é um caso particular de um PBD, em que todos os blocos tem tamanho único 3, sendo chamados de triplas. O foco principal está nas técnicas de construção dos sistemas. Por meio da resolubilidade se discute quando um Sistema Triplo de Steiner é resolvível e quando não é resolvível. Esta teoria possui várias aplicações, por exemplo: imersões e até mesmo problemas relacionados à complexidade computacional.