On Secure Network Coding with Nonuniform or Restricted Wiretap Sets

The secrecy capacity of a network, for a given collection of permissible wiretap sets, is the maximum rate of communication such that observing links in any permissible wiretap set reveals no information about the message. This paper considers secure network coding with nonuniform or restricted wiretap sets, for example, networks with unequal link capacities where a wiretapper can wiretap any subset of $k$ links, or networks where only a subset of links can be wiretapped. Existing results show that for the case of uniform wiretap sets (networks with equal capacity links/packets where any $k$ can be wiretapped), the secrecy capacity is given by the cut-set bound, and can be achieved by injecting $k$ random keys at the source which are decoded at the sink along with the message. This is the case whether or not the communicating users have information about the choice of wiretap set. In contrast, we show that for the nonuniform case, the cut-set bound is not achievable in general when the wiretap set is unknown, whereas it is achievable when the wiretap set is made known. We give achievable strategies where random keys are canceled at intermediate non-sink nodes, or injected at intermediate non-source nodes. Finally, we show that determining the secrecy capacity is a NP-hard problem.Comment: 24 pages, revision submitted to IEEE Transactions on Information Theor

Secure Communication over 1-2-1 Networks

This paper starts by assuming a 1-2-1 network, the abstracted noiseless model of mmWave networks that was shown to closely approximate the Gaussian capacity in [1], and studies secure communication. First, the secure capacity is derived for 1-2-1 networks where a source is connected to a destination through a network of unit capacity links. Then, lower and upper bounds on the secure capacity are derived for the case when source and destination have more than one beam, which allow them to transmit and receive in multiple directions at a time. Finally, secure capacity results are presented for diamond 1-2-1 networks when edges have different capacities.Comment: Submitted for ISIT 201

Secure Communication in Erasure Networks with State-feedback

The security and efficiency of communication are two of the main concerns for networks of today and the future. Our understanding of how to efficiently send information over various channels and networks has significantly increased in the past decade (see e.g., [1–3]), whereas our understanding of how to securely send information has not yet reached the same level. In this thesis, we advance the theory of secure communication by deriving capacity results and by developing coding schemes that provide information-theoretic security for erasure networks. We characterize the highest achievable secret-message rate in the presence of an eavesdropping adversary in various settings, where communication takes place over erasure channels with state-feedback. Our results provide such a characterization for a point-to-point erasure channel, for a broadcast erasure channel with multiple receivers, for a network with multiple parallel channels, a V-network and for a triangle network. We introduce several two-phase secure coding schemes that consist of a key generation phase and an encrypted message sending phase. Our schemes leverage several resources for security: channel erasures, feedback, common randomness and the topology of the network. We present coding schemes for all the above mentioned settings as well as for erasure networks with arbitrary topology. In all the cases where we provide exact characterization, a two-phase scheme achieves the secret-message capacity. All our proposed coding schemes use only linear operations and thus can serve as a basis for practical code designs. For networks, we develop a linear programming framework for describing secure coding schemes and for deriving new outer bounds. We use linear programs to describe our schemes and to prove their optimality. We derive new information theoretic outer bounds. In our intuitive interpretation, our proofs find the connection between the rate of the message and the rate of a secret key that is required to secure the message. Our results reveal nontrivial characteristics of secure communication in erasure networks. We find that – in contrast to non-secure communication – the secret message capacity of a cut does not simplify to the sum of the capacities of the channels that form the cut, moreover, the secret message capacity of a network does not simplify to the minimum secret message capacity of its cuts

Political Advocacy on the Web: Issue Networks in Online Debate Over the USA Patriot Act

This dissertation examines how people and organizations used the World Wide Web to discuss and debate a public policy in 2005, at a point of time when the Internet was viewed as a maturing medium for communication. Combining descriptive and quantitative frame analyses with an issue network analysis, the study evaluated the frames apparent in discourse concerning two key sections of the USA Patriot Act, while the issue network analysis probed hypertext linkages among Web pages where discussion was occurring. Sections 214 and 215 of the USA Patriot Act provided a contentious national issue with multiple stakeholders presumed to be attempting to frame issues connected to the two sections. The focus on two sections allowed frame and issue network contrasts to be made. The study sought evidence of an Internet effect to determine whether the Web, through the way people were using it, was having a polarizing, synthesizing, or fragmentizing effect on discussion and debate. Frame overlap and hypertext linkage patterns among actors in the issue networks indicated an overall tendency toward synthesis. The study also probed the degree to which there is a joining, or symbiosis, of Web content and structure, in part evidenced by whether patterns exist that like-minded groups are coming together to form online community through hypertext linkages. Evidence was found to support this conclusion among Web pages in several Internet domains, although questions remain about linking patterns among blogs due to limitations of the software used in the study. Organizational Web sites on average used a similar number of frames compared to other Web page types, including blogs. The organizational Web pages were found to be briefer in how they discussed issues, however. The study contributes to theory by offering the first known empirical study of online community formation and issue advocacy on a matter of public policy and through its finding of a linkage between Web content and Web structure. Methodologically, the study presents a flexible mixed-methods model of descriptive and quantitative approaches that appears excellently suited for Internet studies. The dissertation’s use of fuzzy clustering and discriminant analysis offer important improvements over existing approaches in factor-based frame analysis and frame mapping techniques

Regulating the technological actor: how governments tried to transform the technology and the market for cryptography and cryptographic services and the implications for the regulation of information and communications technologies

The formulation, adoption, and transformation of policy involves the interaction of actors as they negotiate, accept, and reject proposals. Traditional studies of policy discourse focus on social actors. By studying cryptography policy discourses, I argue that considering both social and technological actors in detail enriches our understanding of policy discourse. The case-based research looks at the various cryptography policy strategies employed by the governments of the United States of America and the United Kingdom. The research method is qualitative, using hermeneutics to elucidate the various actors’ interpretations. The research aims to understand policy discourse as a contest of principles involving various government actors advocating multiple regulatory mechanisms to maintain their surveillance capabilities, and the reactions of industry actors, non-governmental organisations, parliamentarians, and epistemic communities. I argue that studying socio-technological discourse helps us to understand the complex dynamics involved in regulation and regulatory change. Interests and alignments may be contingent and unstable. As a result, technologies can not be regarded as mere representations of social interests and relationships. By capturing the interpretations and articulations of social and technological actors we may attain a better understanding of the regulatory landscape for information and communications technologies

From cyber-utopia to cyber-war: normative change in cyberspace

This dissertation analyzes a normative change in state perception and political action towards the Internet. This change is currently reflected in certain measures aimed at the exercise of control and state sovereignty in and over cyberspace. These include phenomena such as the total surveillance of data streams and the extensive collection of connection data by secret services, the control (political censorship) and manipulation of information (information war) as well as the arms spiral around offensive cyber capabilities to disrupt and destroy information infrastructures. States face a loss of control that they want to compensate for. The phenomenon of the perceived loss of control and the establishment of a norm of control (filter and monitoring technology) is equally evident in various democratic and non-democratic states, as various studies show. This militarized perception of the Internet is remarkable in so far as Western politicians used to perceive the same Internet technology in the 1980s and 1990s in a completely different way. Back then the lack of state control was seen as desirable. Instead of controlling and monitoring all aspects of the Internet, a "hands-off" and laissez-faire idea dominated political behavior at the time: the possibilities of democratization through information technologies, the liberalization of authoritarian societies through technology and the free availability of global knowledge. The idea of national control over communications technology was considered innovation-inhibiting, undemocratic and even technically impossible. The topic of this work is the interaction between state power and sovereignty (e.g. political control through information sovereignty) and digital technologies. The research question is: Which process led to the establishment of norms of control and rule (surveillance, censorship, cyber-war) with regard to the medium Internet? Furthermore, the question arises: What are the implications of this change in standards for the fundamental functioning of the Internet? The aim is to examine in detail the thesis of the militarization of cyberspace empirically on the basis of a longitudinal case study using the example of Internet development in the USA since the 1960s. An interdisciplinary and multi-theoretical approach is chosen from constructivist norms research and the Social Construction of Technology approach

Texas Law Review

Journal containing articles, notes, book reviews, and other analyses of law and legal cases