Browsing by Author "Safavi-Naini, Reihanah"

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    Contributions to Information Theoretically Secure Communication
    (2020-05-15) Sharifian, Setareh; Safavi-Naini, Reihanah; Jacobson, Michael; Williamson, Carey L.; Ruhe, Günther; Simon, Christoph; Narayan, Prakash
    Secure communication ensures the integrity and confidentiality of communication between connected devices. An information-theoretic approach to secure communication gives the strongest confidentiality guarantee by assuming that the attacker has unlimited computing power. The earliest formal model and definition of information-theoretic secure communication is by Shannon, who employed a secret key shared between communicating parties to provide confidentiality. An alternative elegant information-theoretic approach to secure communication views the natural characteristics of the environment (i.e., channel’s noise) as a resource to build security functionalities. This approach was first proposed by Wyner, and the corresponding secure communication model is called the wiretap channel model. These two approaches introduce two primary resources for providing information-theoretic secure communication: the shared secret key and physical properties of the communication medium. In this thesis, we study how to employ the above two resources for secure message transmission. We study this by using channel’s noise in the wiretap channel model. In this model, a sender is connected to the receiver and the adversary through two noisy channels. We propose a new wiretap encoding scheme with strong secrecy that provides perfect secrecy and reliability, asymptotically. The construction treats the noise in the adversary’s channel as a source of randomness that is extracted and used to hide the message from the adversary. We realize the wiretap channel model using cooperative jamming to evaluate the performance of wiretap codes in practice. We consider a model called keyed wiretap channel that unifies Wyner’s model with Shannon’s model of perfect secrecy for information systems, and propose a keyed encoding schemes with strong secrecy and other properties that are attractive in practice. We also study two-party information-theoretic secret key agreement when the two parties have access to samples of a common source of randomness and use a single message transmission to arrive at a shared random key. We propose a secret key agreement protocol in this setting, prove its security, and show its superior performance compared to other known protocols with the same properties. Finally, we propose an information-theoretic secret key agreement over a virtual wiretap channel created by cooperative jamming.
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    Weighted Raft and its Application to Geographically Distributed Servers
    (2018-09-17) Liu, Xi; Safavi-Naini, Reihaneh; Safavi-Naini, Reihanah; Fong, Philip W. L.; Reardon, Joel
    Modern application are usually deployed in a distributed architecture where several servers are involved in providing service to users. Distributed systems offer fault tolerance and increased availability. In some cases, the servers are distributed in different geographic locations to reduce latency and provide better service to end users. Keeping data consistent across servers is a fundamental problem. Raft consensus algorithm has been prepared to achieve data consistency in the presence of server failure. In Raft, servers elect a leader server that manages client-side requests and updates the data files. Each server has the same chance to becoming a leader. Although typical Raft servers are in a local cluster, in many natural applications, Raft can be used in a geographically distributed setting to ensure data consistency. In such a setting, it is natural to allow the “closest” server to a user to respond to the user request. The notation of “closeness” could capture not only geographic location but also network connectivity and capacity. Motivated by the above challenge, we propose Geo-Raft which is the application of Raft protocol in geographically distributed systems. To reduce the performance cost, we add weights to servers’ election timeout to enable the most suitable server to be elected as the leader and serve the users. We propose a model to optimize Geo-Raft performance and present an approach to determine Raft timeouts for a given set of weights. We discuss our results and directions for future work.