Sharif Digital Repository

In this thesis, the problem of secret key agreement in the channel model with side information is studiedx. In order to investigate the problem, we consider three models according to the different ways of side information availability which are the state-dependent broadcast channel; the state-dependent broadcast channel in presence of public channel and the state-dependent wiretap channel with degraded versions of the channel state information.For the problem of secret key agreement in broadcast channels, two models, the state-dependent wiretap channel and state-dependent three receivers broadcast channel, are considered. We obtain inner and outer bounds of the secret key capacity region for... 

In this thesis the problem of simultaneously generating multiple keys among multiple terminals is investigated. After providing a survey on the related works and exploiting the problem of sharing a common secret key and a private key among three terminals, we introduce a new source model which we call it the Four-Terminal model. We consider the problem of generating three kinds of keys among legitimate terminals and investigate the problem under two different scenarios, Backward and Forward scenarios, which depend on the kind of restrictions imposed on the usage of the public channel. We derive an achievable region for the backward scenario, using the combination of superposition coding and... 

In order to utilize cooperative resources of a network, we have to investigate cooperative networks and strategies. Information theory, by introducing different concepts such as coordination and common information, gives us a suitable tool to study cooperative networks and using their resources. In this thesis, we investigate coordination and secret key agreement in cooperative networks. Our study consists of two parts. In the first part, we consider coordination and its applications in cooperative networks. For this purpose, we introduce the triangular multiterminal network as a proper model for studying empirical coordination in multiterminal networks and establish an inner and outer... 

Sharing secret key is an essential prerequisite of symmetric key cryptography. So, we consider a source model for information theoretic secret key agreement based on the distance among the nodes. Secret key agreement based on information theory, unlike computational models, guarantee full information secrecy, eavesdropper receives no efficient information. The model is a basic system consisting of two legitimate users and an eavesdropper. The legitimate nodes try to agree on a reliable and secure key based on their noisy observation of distance between them. Eavesdropper observes the distance, too. First, we model distance estimation by the nodes to study performance of the system (secret... 

Security has been considered from the information theoretic point of view in different channels such as broadcast, multiple access and relay channels. Due to application of these channels in modern networks such as wireless, sensor and Ad-hoc networks, information theoretic security arguments especially wiretapping, has major significance in these networks. With regard to necessity of confidentiality protection in modern telecommunication services, security from the information theoretic point of view should be considered as well as capacity and achievable rate region considerations in these networks. In this thesis, first, a survey of basic works in the subjects of secrecy capacity and... 

Shannon (1948) for the first time defined the "mutual information'' parameter for two random variables, but still there is no common definition for multivariate mutual information has been agreed upon, despite the multitude of research on the subject and various proposed definitions. In 2015, a study suggested that the maximum rate of secret-key, in the secret-key agreement problem, is a suitable candidate for defining multivariate mutual information. Csiszár and Narayan's research on the secret-key agreement problem provides an accessible bound for the maximum rate of secret-key rate, which in the bivariate case is the shannon's mutual information. The proposed definition has all expected... 

The applications of Internet of Things technology are increasing day by day. In the Internet of Things, various devices are connected to each other with the help of the Internet and perform various operations automatically. Today, this technology has various applications in smart city, smart home, smart car, as well as military industries and industrial factories. One of the newest applications is its use in the field of health and hygiene, which is known as the Internet of Medical Things or Smart Health. With the emergence of new epidemic diseases, the importance of this application becomes more clear. Smart health helps the patient. without going to the hospital and doctor in person, to...