In this work, we consider the possibility and the effectiveness of implementing secure network coding and error-correcting network coding at the same time. Upon achieving this goal, information can be multicast securely to the sink nodes through a noisy network. Toward this end, we propose constructions of such codes and prove their optimality. After that, we extend the idea of generalized Hamming Weight [54] for the classical point-to-point communication channel to linear network coding. We also extend the idea of generalized Singleton bound to linear network coding. We further show that the generalized Hamming weight can completely characterize the security performance of linear code at the source node on a given linear network code. We then introduce the idea of Network Maximum Distance Separable code (NMDS code), which can be shown to play an important role in minimizing the information that an eavesdropper can obtain from the network. The problem of obtaining the optimal security performance is in fact equivalent to the problem of obtaining a Network Maximum Distance Separable code. / Network coding is one of the most important breakthroughs in information theory in recent years. The theory gives rise to a new concept regarding the role of nodes in a communication network. Unlike in existing networks where the nodes act as switches, in the paradigm of network coding, every node in the network can act as an encoder for the incoming information. With this new infrastructure, it is possible to utilize the full capacity of the network where it is impossible to do so without network coding. In the seminar paper by Ahlswede et al. [1] where network coding was introduced, the achievability of the maxflow bound for every single source multicast network by using network coding was also proved. By further exploring the possibility of linear network coding, Cai and Yeung introduced the idea of error-correcting network coding and secure network coding in [7] and [8] respectively. These papers launched another two important research areas in the field of network coding. / Ngai, Chi Kin. / Adviser: Yqung Wai Ho. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3696. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 122-128). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

With the development of the information network technologies and the popularisation of the Internet, Chinese society is experiencing a Triple Revolution. Regulating the Internet has become a priority in China. In this context, this study seeks a comprehensive and in-depth understanding of China's Internet regulatory mechanism. Through the systematical analysis on Internet law in China, supplemented by the case study on how the issue of the Occupy Movement in Hong Kong was regulated, this study argues that China has developed a hybrid Internet regulatory model, which values both external defense and internal control in pursuit of the goal of cybersecurity, and which combines hierarchical regulation with horizontal monitoring to address challenges brought by contemporary network society. The Internet panoptic-fortification model is developed to illuminate China's Internet regulatory mechanism. The Internet panoptic-fortification model is featured by the centralised control from the authorities and ISPs, the establishment of Chinese sovereign cyberspace with jurisdictional and technical supports, the implementation of the network real-name system and the Internet-surfing record backup system to regulate individual Internet users, and the tight ideological control. This conceptual model reflects important aspects of Michel Foucault's account of governmentality, incorporating both centralised power and diffuse micro-power. This study suggests that China's Internet law to some extent has become an instrument for the state to promote the social discipline in the sovereign cyberspace, and the Internet regulatory mechanism serves for the national security and social stability in a broader context.

M.Sc. (Computer Science) / The terms "Electronic Commerce" and "Internet Commerce" are often used interchangeably to mean similar processes. By definition, electronic commerce (e-commerce) means any exchange of information that occurs electronically. There are various types of electronic commerce transactions to name a few; electronic data interchange (EDI), fax, electronic funds transfer, interorganisational systems, technical data and document exchange, customer credit approval systems, interaction with customers and vendors, etc ([151, p. 27). The term internet commerce evolved with the era of the Internet. It became evident that both business and consumers are gradually conducting business via the Internet. For the purpose of this dissertation the term e-commerce will be used to refer to both electronic commerce and Internet commerce. The aim of this dissertation is to give guidance to organisations or individuals wishing to build a secure electronic commerce environment. This will be achieved by presenting an incremental phase by phase reference model. The model gives guidance on how to establish a network (local area network) with the intention to expand it through various phases to a complete, secure electronic commerce environment in the future. The dissertation will be discussed in the ten chapters outlined below. These chapters are discussed in detail in chapter 1. Chapter 1 sets out the problem addressed in this dissertation, the main objective of the dissertation and its structure. Chapter 2 introduces the framework of the reference model. It presents the different phases of the e-commerce reference model. Chapters 3 to 8 outline the phases of the e-commerce reference model in detail.

Thesis (MPhil)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: The business and social environments are increasingly reliant on the information network, and the quality and integrity of the information to effectively conduct transactions, and "survive" in the new economy. These information networks facilitate communication and transactions between customers, suppliers, partners, and employees. Emerging technologies further encourage the extension of network boundaries beyond the branch office, to private homes, airports, and even the comer coffee shop, e.g. wireless internet access. Although technology advances contribute to significant increases in productivity, convenience, and competitive advantage, it also increases the risk of attacks on the integrity and confidentiality of any information interaction. One of the key questions is how to achieve the right level of information network security and implement effective protection systems, without impacting productivity by excessively restricting the flow of information. The issue of information security is not a localised problem, but a problem on global scale, and South African businesses are no less at risk than any other geographically located business. The risk of information security is even greater if aspects like globalisation are taken into account, and the growing inter-connectedness of the global business environment. The central question is: How does the South African business environment view information security, their perceived success in implementing information security measures, and their view of future trends in information security. Ingenue- Consulting is a global business focusing on technology consulting services, across a wide range of industries and technologies. Information security has been identified by Ingenue Consulting to be a global problem, and primary research into this business issue have been undertaken in different locations globally, e.g. Australia and South African executive level survey of what the perception and importance are of information security, of business leaders across public and private industries. Ingenue Consulting has an in-house research facility, and tasked them with conducting a survey in South Africa. The survey results can then be compared with global trends, and applied in the business environment, to highlight the impact of information security risks, and to help businesses to change and improve their information security processes and technologies. The research department started out doing an extensive literature study to identify global and local trends in information security, and to assist in the compilation of the survey questionnaire. A sample group of "blue chip" businesses across all industries was targeted at executive level to conduct a research survey - fifty interviews were conducted. The raw data was collated and analysed to formulate an opinion of the information security practices and perceptions of the business environment in South Africa. The survey confirmed that the South African market risks in terms of information security are very similar to global trends. Some of the key trends are: Information security agreements are normally signed at the onset of employment, but rarely updated or highlighted to ensure continued support and implementation. This is almost contradictory to the fact that information security are taken seriously by the executive level, and often discussed at board level. The mobility of information with the emergence of wireless networks is a key issue for most businesses - as information security is at its most vulnerable. Most of the respondents rated themselves ahead of the curve and their competitors - overestimation of competencies, could lead to larger future risks. The sensitive nature of information security industry makes benchmarking against local or global players difficult due to the sensitive nature -limited willingness to participate in a consultative forum. Companies that outsouree IT tend to "wash their hands off' security issues as the responsibility of the outsourcing vendor. Most local businesses haven't got a worldly view - they do not have an active process to find out what their peers are doing locally or globally, they rely mostly on vendor and consulting advice, or media coverage. / AFRIKAANSE OPSOMMING: Die besigheids en sosiale omgewings is toenemend afhanklik van die inligtings netwerke, en die kwaliteit en integriteit van inligting om transaksies effektief uit te voer, en om te "oorleef" in die nuwe ekonomie. Inligtings netwerke fasiliteer kommunikasie en transaksies tussen kliente, verskaffers, vennote, en werknemers. Nuwe tegnologiee verder veskuif netwerk grense, wyer as die tak-kantoor, na private huise, lughawens, of die koffie kafee - deur middel van draadlose internet toegang. Alhoewel tegnologie ontwikkelings bydra tot verbeterde produktiwiteit, en gemak van gebruik - dra dit ook by tot groter gevaar van aanvalle op die integriteit en konfidensialiteit van enige inligtings transaksie. Een van die sleutel vrae is hoe om die regte vlak van inligting netwerk sekuriteit te bereik, en om die regte beskermings metodes te implementeer - sonder om die produtiwiteit te inhibeer. Die inligting sekuritets vraagstuk is nie bloot 'n lokale vraagstuk nie, maar van globale skaal, en Suid-Afrikaanse besighede is nie minder in gevaar as enige ander besigheid in 'n ander lande nie, veral nie as aspekte soos globaliseering in ag geneem word nie. Die sentrale vraag is: Hoe sien die Suid-Afrikaanse besigheids wereld inligtings sekuriteit, en die waargenome sukses met die implementering van inligtings sekuriteit prosesse, en ook hoe hul die toekoms sien van inligtings sekuriteit. Ingenue* Consulting is 'n wereldwye besigheid, gefokus op tegnologie konsultasie dienste, oor 'n wye reeks industriee en tegnologiee. Inligting sekuriteit is deur Ingenue Consulting ge-identifiseer as 'n globale probleem, en primere navorsing in die area is al onderneem in verskillende geografiee, soos Australie en die Verenigde Koninkryk. Die Suid-Afrikaanse tak van Ingenue het vroeg in 2004 besluit om 'n lokale studie te doen oor top bestuur se persepsies van inligting sekuriteits risikos, in beide die publieke en privaat besigheids wereld. Die interne navorsings afdeling van Ingenue Consulting in Suid-Afrika is gevra om die nodige studie te ondeneem, om dit dan met globale studies te vergelyk, en te kan bepaal waar gapings mag wees, en hoe om die gapings aan te spreek. Die navorsings afdeling het begin deur 'n ekstensiewe literatuur studie te doen, as hulp tot die samestelling van die vrae-lys. 'n Teiken groep van top Suid-Afrikaanse besighede, verteenwoordigend van alle industriee is genader om 'n onderhoud toe te staan om die vrae-lys te voltooi - vyftig onderhoude was voltooi. Die rou data is gekollekteer en geanaliseer, om 'n opinie te formuleer oor die inligtings sekuriteit persepsies en praktyke van die besigheids omgewing in Suid-Afrika. Die navorsing het bevestig dat die Suid-Afrikaanse mark baie dieselfde is as ander geografiese markte - in terme van inligting sekuriteit. Van die sleutel konklusies is: Inligting sekuriteit ooreenkomste word meestal geteken met die aanvangs van diens, maar bitter selde dan weer opgevolg of hernu - dit is byna kontradikterend dat top bestuur ook baie besorg is oor inligting sekuriteit, en dat dit dikwels by raads vergaderings bespreek word. Die mobiliteit van inligting is 'n groeiende bekommernis, omrede inligting dan nog meer op risiko is. Meeste respondente sien hulself as beter of meer gevorderd as hul kompeteerders - 'n oor-estimasie van sukses in inligtings sekuriteit kan lei tot groter probleme in die toekoms. Die sensitiewe natuur van inligting sekuriteit maak ope vergelyking van gedetaileerde prosesse moeilik - en meeste besighede is nie bereid om deel te neem aan algemene gesprekke nie. Terwyl besighede wat hul tegnologie afdeling deur 'n derde party bestuur, neem geen verantwoordelikheid vir hul inligtings sekuriteit nie. 'n Groter bekommernis is dat besighede in Suid-Afrika nie 'n aktiewe proses het om op hoogte bly van wat die beste opsies is in inligtings sekuriteit nie, of wat hul teenstanders doen nie - maar vertrou op die advies van verkoops en konsultasie maatskappye, of media berigte.