Browsing by Author "Sharifian, Setareh"

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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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    Random Number Generation using Human Gameplay
    (2016) Sharifian, Setareh; Safavi-Naini, Reihaneh
    Randomness is one of the most important research areas in computer science and in particular, in cryptography. Security of almost all cryptosystems relies on random keys. Unfortunately, perfect sources of randomness are not easily accessible. However, True Random Number Generators (TRNGs) generate almost random strings, using non-perfect random sequences. A TRNG algorithm consists of an entropy source and an extractor. In this thesis, a TRNG is proposed in which a human player’s input in a two-player game is used as the entropy source and the random seed required by the extractor. This means that the proposed TRNG is only dependent on user’s inputs. The thesis contains the theoretical foundation of the approach, the design, and implementation of the corresponding game. To validate theories, we designed and implemented a game, and performed some user studies. The results of our experiments support the effectiveness of the proposed method in generating high-quality randomness.