Cloud Based Data Protection in Anonymously Controlled SDN

Nowadays, Software Defined Network (SDN) develops rapidly for its novel structure which separates the control plane and the data plane of network devices. Many researchers devoted themselves to the study of such a special network. However, some limitations restrict the development of SDN. On the one hand, the single controller in the conventional model bears all threats, and the corruption of it will result in network paralysis. On the other hand, the data will be increasing more in SDN switches in the data plane, while the storage space of these switches is limited. In order to solve the mentioned issues, we propose two corresponding protocols in this paper. Specifically, one is an anonymous protocol in the control plane, and the other is a verifiable outsourcing protocol in the data plane. The evaluation indicates that our protocol is correct, secure, and efficient

BigDipper: A hyperscale BFT system with short term censorship resistance

Byzantine-fault-tolerant (BFT) protocols underlie a variety of decentralized applications including payments, auctions, data feed oracles, and decentralized social networks. In most leader-based BFT protocols, an important property that has been missing is the censorship resistance of transaction in the short term. The protocol should provide inclusion guarantees in the next block height even if the current and future leaders have the intent of censoring. In this paper, we present a BFT system, BigDipper, that achieves censorship resistance while providing fast confirmation for clients and hyperscale throughput. The core idea is to decentralize inclusion of transactions by allowing every BFT replica to create their own mini-block, and then enforcing the leader on their inclusions. To achieve this, BigDipper creates a modular system made of three components. First, we provide a transaction broadcast protocol used by clients as an interface to achieve a spectrum of probabilistic inclusion guarantees. Afterwards, a distribution of BFT replicas will receive the client's transactions and prepare mini-blocks to send to the data availability (DA) component. The DA component characterizes the censorship resistant properties of the whole system. We design three censorship resistant DA (DA-CR) protocols with distinct properties captured by three parameters and demonstrate their trade-offs. The third component interleaves the DA-CR protocols into the consensus path of leader based BFT protocols, it enforces the leader to include all the data from the DA-CR into the BFT block. We demonstrate an integration with a two-phase Hotstuff-2 BFT protocol with minimal changes. BigDipper is a modular system that can switch the consensus to other leader based BFT protocol including Tendermint

Towards practicalization of blockchain-based decentralized applications

Blockchain can be defined as an immutable ledger for recording transactions, maintained in a distributed network of mutually untrusting peers. Blockchain technology has been widely applied to various fields beyond its initial usage of cryptocurrency. However, blockchain itself is insufficient to meet all the desired security or efficiency requirements for diversified application scenarios. This dissertation focuses on two core functionalities that blockchain provides, i.e., robust storage and reliable computation. Three concrete application scenarios including Internet of Things (IoT), cybersecurity management (CSM), and peer-to-peer (P2P) content delivery network (CDN) are utilized to elaborate the general design principles for these two main functionalities. Among them, the IoT and CSM applications involve the design of blockchain-based robust storage and management while the P2P CDN requires reliable computation. Such general design principles derived from disparate application scenarios have the potential to realize practicalization of many other blockchain-enabled decentralized applications. In the IoT application, blockchain-based decentralized data management is capable of handling faulty nodes, as designed in the cybersecurity application. But an important issue lies in the interaction between external network and blockchain network, i.e., external clients must rely on a relay node to communicate with the full nodes in the blockchain. Compromization of such relay nodes may result in a security breach and even a blockage of IoT sensors from the network. Therefore, a censorship-resistant blockchain-based decentralized IoT management system is proposed. Experimental results from proof-of-concept implementation and deployment in a real distributed environment show the feasibility and effectiveness in achieving censorship resistance. The CSM application incorporates blockchain to provide robust storage of historical cybersecurity data so that with a certain level of cyber intelligence, a defender can determine if a network has been compromised and to what extent. The CSM functions can be categorized into three classes: Network-centric (N-CSM), Tools-centric (T-CSM) and Application-centric (A-CSM). The cyber intelligence identifies new attackers, victims, or defense capabilities. Moreover, a decentralized storage network (DSN) is integrated to reduce on-chain storage costs without undermining its robustness. Experiments with the prototype implementation and real-world cyber datasets show that the blockchain-based CSM solution is effective and efficient. The P2P CDN application explores and utilizes the functionality of reliable computation that blockchain empowers. Particularly, P2P CDN is promising to provide benefits including cost-saving and scalable peak-demand handling compared with centralized CDNs. However, reliable P2P delivery requires proper enforcement of delivery fairness. Unfortunately, most existing studies on delivery fairness are based on non-cooperative game-theoretic assumptions that are arguably unrealistic in the ad-hoc P2P setting. To address this issue, an expressive security requirement for desired fair P2P content delivery is defined and two efficient approaches based on blockchain for P2P downloading and P2P streaming are proposed. The proposed system guarantees the fairness for each party even when all others collude to arbitrarily misbehave and achieves asymptotically optimal on-chain costs and optimal delivery communication

Design and Evaluate a Fair Exchange Protocol Based on Online Trusted Third Party (TTP)

One of the most crucial factors that e-commerce protocols should address is a fair exchange. In this research, an advanced method of cryptography coupled with the pay per use technique is used. A new electronic commerce protocol for the exchange of commodities is introduced. The proposed new protocol guarantees both features while addressing the main drawbacks associated with other related protocols. The new suggested e-commerce protocol is composed of two stages: pre-exchange and exchange stages. When the suggested new protocol is analysed with scrupulous protocol analysis, it attains fair exchange and a secure method of payment. The suggested new e-commerce protocol is more efficient than other related existing protocols. In this research “protocol prototype” and “model checking” is used for the purpose of authentication. The protocol prototype verifies that the suggested new protocol is executable when it's used in a real context. By experimental designs, this research shows the length of asymmetric keys as the biggest element that affects the efficiency of the protocol. When model-checking is applied in this protocol, the outcome indicates that the suggested protocol achieves the required features of fairness. Protocol extensions give those involved in the protocol the capacity to be resilient to failure. By using three methods of authentication, this research confirms that the new proposed protocol is well formulated. The work reported in this thesis first study the existing fair exchange protocols that solve the fairness problem. Then, propose more efficient protocol to solve the fairness problem. The original idea in this thesis is to reduce the communication overheads, risks and solve the bottleneck problems in the protocols that involve an online TTP

Addressing the problem of sterile drug injecting supply acquisition for people who inject drugs.

This dissertation contains five chapters, including three manuscripts, covering harm reduction and some of the challenges people who inject drugs (PWID) face in their effort to reduce the risk of injection drug-related harms through sterile injecting supply acquisition and use. Chapter One discusses some background related to PWID and provides an overview of the issues addressed in this dissertation. Chapter Two includes a literature review covering the harm reduction concept, important aspects of syringe exchange programs as a harm reduction tool, and the social determinants of health model as a potential tool for future research. Chapter Three is a two-phase study that examines the problem of syringe and drug injecting equipment sharing and reuse among PWID participating in a syringe exchange program. This study explores the scope of the problem, then uncovers reasons contributing to syringe sharing and reuse behavior. Findings are applied to the social determinants of health model, with results demonstrating a number of social determinants that influence PWID behavior. In Chapter Four the author highlights approaches to sterile drug injecting supply acquisition used by PWID and presents policy alternatives. Finally, there is a discussion of a case study and description of how nurses can ethically support harm reduction strategies for PWID. Chapter Five contains a summary of findings and recommendations for future work

Strategies to Reduce Employee Turnover in the Hotel Industry

Hotel leaders face reduced profitability because of high employee turnover. Using Herzberg\u27s 2-factor theory as the conceptual framework, the purpose of this multiple case study was to explore strategies that some hotel human resources managers used to reduce employee turnover. Data were collected from 5 hotel human resources managers in Massachusetts through face-to-face, semistructured interviews and a review of company documents. Data analysis using Yin\u27s 5-step process of compiling, disassembling, reassembling, interpreting, and developing data-based conclusions resulted in 3 emergent themes: a retention strategy, a compensation strategy, and a training and development strategy. The findings indicated that the employee recruitment process, fair employee compensation and benefits, a focus on employee development, and recognition and appreciation of employees were pivotal strategies human resources managers used to reduce employee turnover. The findings may be valuable to hotel general managers, human resources managers, authors of training manuals, and hiring managers for creating strategies to reduce employee turnover. The implications for positive social change include the potential for hotel general managers to lower unemployment rates and improve the quality of life for the local community through lower employee turnover

Strategies to Retain Millennial Employees at Full-Service Restaurants

Some supervisors lack effective strategies to retain millennial generation employees. The purpose of this multicase study was to explore effective strategies supervisors use to retain culinary-educated millennial employees in full-service restaurants. Nine millennials and 3 supervisors from 3 full-service restaurants in Denver, Colorado consented to face-to-face semistructured interviews with open-ended interview questions concerning retention strategies. The conceptual framework of Herzberg\u27s two-factor theory served to guide the scope and the data analysis for the multicase study. The interview transcripts were coded and grouped into themes. Explanation building for the data analysis assisted in finding causal links between cases and the unit of analysis, and in assembling a broad explanation to fit each case. Ten subcategories emerged from the 3 themes that aligned with Herzberg\u27s motivation factors, hygiene factors, and millennial values and attitudes. The 10 subcategories were developed, and indicated that effective strategies differ by supervisor. Among the ten subcategories, the most prominent were (a) growth and advancement, (b) positive working conditions, and (c) quality and influence of the supervisor. This study may contribute to social change by providing restaurant supervisors with strategies for millennial retention and keeping young workers in the community to share in the responsibility of social progress and to reach their full potential

Decentralised computer systems

The architecture of the Web was designed to enable decentralised exchange of information. Early architects envisioned an egalitarian yet organic society thriving in cyberspace. The reality of the Web today, unfortunately, does not bear out these visions: information networks have repeatedly shown a tendency towards consolidation and centralisation with the current Web split between a handful of large corporations. The advent of Bitcoin and successor blockchain networks re-ignited interest in developing alternatives to the centralised Web and paving a way back to the earlier architectural visions for the Web. This has led to immense hype around these technologies with the cryptocurrency market valued at several hundred billions of dollars at the time of writing. With great hype, apparently, come great scams. I start off by analysing the use of Bitcoin as an enabler for crime and then present both technical solutions as well as policy recommendations to mitigate the harm these crimes cause. These policy recommendations then lead us on to look more closely at cryptocurrency's tamer cousin: permissioned blockchains. These systems, while less revolutionary in their premise, nevertheless aim to provide sweeping improvements in the efficiency and transparency of existing enterprise systems. To see whether they work in practice, I present the results of my work in delivering a production permissioned blockchain system to real users. This involves comparing several permissioned blockchain systems, exploring their deficiencies and developing solutions for the most egregious of those. Lastly, I do a deep dive into one of the most persistent technical issues with permissioned blockchains, and decentralised networks in general: the lack of scalability in their consensus mechanisms. I present two novel consensus algorithms that aim to improve upon the state of the art in several ways. The first is designed to enable existing permissioned blockchain networks to scale to thousands of nodes. The second presents an entirely new way of building decentralised consensus systems utilising a trie-based data structure at its core as opposed to the usual linear ledgers used in current systems