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Title Information-Theoretically Secure Communication Under Channel Uncertainty
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University/Publisher Texas A&M University
Abstract Secure communication under channel uncertainty is an important and challenging problem in physical-layer security and cryptography. In this dissertation, we take a fundamental information-theoretic view at three concrete settings and use them to shed insight into efficient secure communication techniques for different scenarios under channel uncertainty. First, a multi-input multi-output (MIMO) Gaussian broadcast channel with two receivers and two messages: a common message intended for both receivers (i.e., channel uncertainty for decoding the common message at the receivers) and a confidential message intended for one of the receivers but needing to be kept asymptotically perfectly secret from the other is considered. A matrix characterization of the secrecy capacity region is established via a channel-enhancement argument and an extremal entropy inequality previously established for characterizing the capacity region of a degraded compound MIMO Gaussian broadcast channel. Second, a multilevel security wiretap channel where there is one possible realization for the legitimate receiver channel but multiple possible realizations for the eavesdropper channel (i.e., channel uncertainty at the eavesdropper) is considered. A coding scheme is designed such that the number of secure bits delivered to the legitimate receiver depends on the actual realization of the eavesdropper channel. More specifically, when the eavesdropper channel realization is weak, all bits delivered to the legitimate receiver need to be secure. In addition, when the eavesdropper channel realization is strong, a prescribed part of the bits needs to remain secure. We call such codes security embedding codes, referring to the fact that high-security bits are now embedded into the low-security ones. We show that the key to achieving efficient security embedding is to jointly encode the low-security and high-security bits. In particular, the low-security bits can be used as (part of) the transmitter randomness to protect the high-security ones. Finally, motivated by the recent interest in building secure, robust and efficient distributed information storage systems, the problem of secure symmetrical multilevel diversity coding (S-SMDC) is considered. This is a setting where there are channel uncertainties at both the legitimate receiver and the eavesdropper. The problem of encoding individual sources is first studied. A precise characterization of the entire admissible rate region is established via a connection to the problem of secure coding over a three-layer wiretap network and utilizing some basic polyhedral structure of the admissible rate region. Building on this result, it is then shown that the simple coding strategy of separately encoding individual sources at the encoders can achieve the minimum sum rate for the general S-SMDC problem.
Subjects/Keywords Channel uncertainty; secure communication; MIMO secure communication; security embedding; secure symmetrical multilevel diversity coding; secure distributed storage systems; physical-layer security
Contributors Liu, Tie (advisor); Savari, Serap (committee member); Jiang, Anxiao (Andrew) (committee member); Shakkottai, Srinivas (committee member)
Language en
Country of Publication us
Record ID handle:1969.1/ETD-TAMU-2012-05-10822
Repository tamu
Date Retrieved
Date Indexed 2017-09-06
Issued Date 2012-07-16 00:00:00

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…understand the fundamental limitations of the security embedding. 3. Secure symmetrical multilevel diversity coding. This source coding problem is motivated by recent interest on building secure, robust and efficient distributed information storage systems…

…transmitter randomness to protect the high-security ones. Finally, motivated by the recent interest in building secure, robust and efficient distributed information storage systems, the problem of secure symmetrical multilevel diversity coding (S-SMDC…

…viii CHAPTER Page C. Secure Symmetrical Multilevel Diversity Coding 1. Problem Statement . . . . . . . . . . . . . 2. Main Results . . . . . . . . . . . . . . . . . 3. Proof of the Main Results . . . . . . . . . . D. Concluding Remarks…

…theoretic security. In his seminal paper [2], Shannon defined a secrecy system to be perfectly secure if the cipher text is statistically independent of the message. Note that this is the strongest notion of security, as observing cipher text now…

…asymptotically perfectly secret from the eavesdropper. No secret key is needed to achieve asymptotically perfectly secure communication. This result was later extended to the general broadcast channel by Csisz´ ar and K¨ orner [4]. The line of research…

…channel model of Wyner [3] and Csisz´ arK¨ orner [4] to more complex and realistic secure communication scenarios under channel uncertainty. In particular, we take a fundamental information-theoretic view at three concrete settings and…

…use them to shed insight into efficient secure communication techniques for different scenarios under channel uncertainty. 1. Broadcast channels with common and confidential messages. Here, in addition to the confidential message, there is also a…

…Which realization actually materializes is unknown to the transmitter a priori (i.e., channel uncertainty at the eavesdropper). Our goal is to design coding schemes such that the number of secure 5 bits delivered to the legitimate receiver…

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