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    Towards implementing RSA-based CP-ABE algorithm on Android system : a thesis presented in partial fulfilment of the requirements for the degree of Master of Information Sciences at Massey University, Auckland, New Zealand
    (Massey University, 2019) Xing, Jiaxin
    Cipher-text-Policy Attribute-Based Encryption (CP-ABE) algorithm has been proposed to encrypt and decrypt data based on the matching between attributes and an access policy placed over cipher-text. Using CP-ABE, data owner can encrypt data along with an access policy to enforce a fine-grained access control. To improve the efficiency of performance, this study chose a RSA-based CP-ABE algorithm with an access-tree structure while most existing CP-ABE has been implemented using ECC. This new RSA-based CP-ABE algorithm was implemented in the Linux system in another study while this thesis addresses an implementation strategy on an Android system. To achieve this goal, a simple encryption application was designed for users who want to encrypt and decrypt messages through their mobile devices. This study used Android Studio to create the encryption application. In this cipher program, users input the message they want to encrypt and get the encrypted data through the function button named “CIPHER”, and they also can decrypt the cipher-text in the same way. There are four main algorithms involved in a CP-ABE scheme. They respectively are setup, key generation, encryption and decryption. During the setup process, the CP-ABE scheme uses the RSA algorithm to choose two prime numbers. These prime numbers are used to a master public key and a master private key. In the key generation algorithm, a secret key is generated for a set of attributes using the master private key. In the encryption step, it creates a cipher-text with an access tree. In the decryption algorithm, if and only if the attributes for the user’s decryption key satisfies this access policy is able to decode the encrypted data. This algorithm uses the construction of lightweight no-paring crypto-system based on RSA, and the construction supports an expressive monotone tree access structure to implement the complex access control as a more generic system. By using this algorithm, the encryption and decryption processes are more efficient and secure.
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    Increasing the capacity of 5G networks using mobile-cells : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, New Zealand
    (Massey University, 2019) Jaffry, Shan
    Recently, the exponential growth in mobile data demand, fuelled by novel use-cases, such as high- definition video streaming, etc., has caused massive strain on cellular networks. As a solution, the fifth generation (5G) of cellular technology has been introduced to improve network performance through various innovative features, such as millimeter-wave spectrum, device-centric communication, and heterogeneous networks (HetNet). The HetNets will comprise of several small-cells underlaid within macro-cell to serve densely populated regions, like stadiums, malls, etc. On the other hand, due to the constant rise in the use of mobile phones while traveling, the concept of mobile-cells has emerged. Mobile-cells may well be defined as public transport vehicles (e.g., buses or trains etc.) equipped with in- vehicle cellular antenna to serve commuters. The argument for using mobile-cell is based on the observation that commuters often experience poor quality of service (QoS) due to vehicular penetration loss (VPL). Mobile-cell will decouple commuters from the core network, thus eliminating VPL, along with relieving base station off large number of users. Mobile-cells will contain multiple wireless links. Commuters will be served over access link (AL), while the communication with the core network will occur over the backhaul link (BL). On the other hand, neighboring mobile-cells will mutually exchange data over sidehaul links (SLs). Like any other device-centric communication, mobile-cells need to ‘discover’ their neighbors before establishing SLs. Neighborhood discovery is challenging for mobile-cells. Relevant literature on this topic has only focused on static devices, and discovery for mobile devices has not been investigated in detail. Hence, as our first research problem in this thesis, we have focused on the autonomous discovery by a mobile-cell. In general, due to randomness involved in an autonomous process, neighborhood discovery often fails due to collision and half-duplexing effects. This thesis focuses on mitigating these effects. Firstly, we have proposed a modified time-frequency frame structure to subside the collision and half-duplexing effects. Later on, we have presented a more reliable solution that utilizes proximity awareness to adapt transmission probability of individual devices. This scheme has resulted in a drastic increase in the probability of successful discovery as compared to the conventional approaches. On the other hand, actual data exchange via mobile-cell’s links requires interference-free resource allocation for each link. Mobile-cells’ wireless links will cause severe interference to the out-of-vehicle cellular users. Few researchers have assigned separate bands for in-vehicle and out-of-vehicle links. However, given the scarcity of spectral resources, these methods are practically inefficient. Thus, we have addressed the issue of resource allocation as the second research problem in this thesis. Instead of assigning individual resources to each link, we have focused on resource sharing between multiple wireless links. To achieve this goal, we have exploited VPL and utilized successive interference cancellation. Our results have shown high QoS at each individual link. We have also demonstrated the effect of mobility on the proposed resource sharing schemes. The schemes proposed in this thesis will ensure that the mobile-cell increases the capacity of 5G networks through aggressive resource sharing such that more links will use available spectral resources.
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    Encryption key management in wireless ad hoc networks : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computer Science at Massey University, Auckland, New Zealand
    (Massey University, 2010) Nisbet, Alastair Jon
    Communication is an essential part of everyday life, both as a social interaction and as a means of collaboration to achieve goals. Networking technologies including the Internet have provided the ability to communicate over distances quickly and effectively, yet the constraints of having to be at a computer connected to a network access point restricts the use of such devices. Wireless technology has effectively released the users to roam more freely whilst achieving communication and collaboration, and with worldwide programs designed to increase laptop usage amongst children in developing countries to almost 100%, an explosive growth in wireless networking is expected. However, wireless networks are seen as relatively easy targets for determined attackers. Security of the network is provided by encrypting the data when exchanging messages and encryption key management is therefore vital to ensure privacy of messages and robustness against disruption. This research describes the development and testing through simulation of a new encryption key management protocol called SKYE (Secure Key deploYment & Exchange) that provides reasonably secure and robust encryption key management for a mobile ad hoc network. Threshold cryptography is used to provide a robust Certificate Authority providing certificate services to the network members using Public Key Infrastructure. The protocol is designed to be used in an environment where communications must be deployed quickly without any prior planning or prior knowledge of the size or numbers of the potential members. Such uses may be many and varied and may include military, education or disaster recovery where victims can use the protocol to quickly form ad hoc networks where other communication infrastructure has failed. Many previous protocols were examined and several key features of these schemes were incorporated into this protocol along with other unique features. These included the extensive tunability of the protocol allowing such features as increasing the number of servers that must collaborate to provide services and the trust level that must exist along a certificate chain before a request for a certificate will be accepted by a server. The locations of the servers were carefully selected so that as these parameters were altered to increase security, performance remained high. For example, when two servers were required for certificate issuance, a certificate request would succeed 92% of the time. By doubling the servers required and therefore considerably increasing resilience against attack of the certificate authority, this figure dropped only moderately to 78%. The placement of the servers proved to be a critical parameter and extensive experiments were run to identify the best placements for servers with the various parameters chosen. Simulations show that the protocol performs effectively in a developing and constantly changing network where nodes may join and leave the network frequently and where many of the members may be mobile. The many tunable parameters of the protocol ensure that it is useful in a variety of applications and has unique features making it effective and efficient in a highly dynamic network environment.