Policy resolution of shared data in online social networks

Online social networks have practically a go-to source for information divulging, social exchanges and finding new friends. The popularity of such sites is so profound that they are widely used by people belonging to different age groups and various regions. Widespread use of such sites has given rise to privacy and security issues. This paper proposes a set of rules to be incorporated to safeguard the privacy policies of related users while sharing information and other forms of media online. The proposed access control network takes into account the content sensitivity and confidence level of the accessor to resolve the conflicting privacy policies of the co-owners

Blockchain for Transparent Data Management Toward 6G

The wealth of user data acts as a fuel for network intelligence toward the sixth generation wireless networks (6G). Due to data heterogeneity and dynamics, decentralized data management (DM) is desirable for achieving transparent data operations across network domains, and blockchain can be a promising solution. However, the increasing data volume and stringent data privacy-preservation requirements in 6G bring significantly technical challenge to balance transparency, efficiency, and privacy requirements in decentralized blockchain-based DM. In this paper, we investigate blockchain solutions to address the challenge. First, we explore the consensus protocols and scalability mechanisms in blockchains and discuss the roles of DM stakeholders in blockchain architectures. Second, we investigate the authentication and authorization requirements for DM stakeholders. Third, we categorize DM privacy requirements and study blockchain-based mechanisms for collaborative data processing. Subsequently, we present research issues and potential solutions for blockchain-based DM toward 6G from these three perspectives. Finally, we conclude this paper and discuss future research directions.Huawei Technologies Canada || Natural Sciences and Engineering Research Council of Canad

DİJİTAL DÖNÜŞÜMDE BLOKZİNCİR TEKNOLOJİSİ ve BITCOIN’İN EKONOMİYE ETKİSİ

DİJİTAL DÖNÜŞÜMDE BLOKZİNCİR TEKNOLOJİSİ ve BITCOIN’İN EKONOMİYE ETKİSİ Özgür GÜVEN Yüksek Lisans Tezi, Ekonomi ve Finans Anabilim Dalı Tez Danışmanı: Dr. Öğr. Üyesi Şahin BULUT 2020, XIII + 84 sayfa Teknolojinin hayatı kolaylaştıran etkisi finansal enstrümanlarda bitcoin ile kendini göstermiştir. Bitcoin, 2009 yılında ortaya çıkmasının ardından ödeme sistemlerinde devrim niteliğinde bir altyapı sunan kripto para türüdür. Bitcoinin temel teknolojisi olan blokzincir, güvenilir bir üçüncü tarafa ihtiyaç duymayan, merkezi olmayan bir sistem olarak tasarlanmış; geniş uygulama potansiyeli ile kamu ve iş dünyasında hızla kabul görmüştür. Bu teknolojik altyapı üzerinde geliştirilen kripto paralar ile birey ya da kurumlar nakit parayla yapılan her türlü harcamayı ve para transferini gerçekleştirmektedir. Bu çalışmada, Ocak 2012 – Mart 2020 tarihleri arasında cumhuriyet altını, altın ons fiyatı, ham petrol fiyatı, amerikan doları ve euro para birimleri ile bitcoin arasındaki korelasyon ilişkisi incelenmiştir. Araştırma kapsamında tanımlayıcı istatistikler, Spearman korelasyon analizinden faydalanılarak yapılmıştır. Yapılan analizlerinin sonucuna göre piyasalarda yer edinmeye başladığı ilk dönem olan 2012’de bitcoinin diğer göstergelerle arasında istatistiksel olarak anlamlı bir ilişkisi saptanmamıştır (p>0.05). Bitcoinin dolar karşılığının bir önceki yıla göre üç katından fazla arttığı 2017 yılı ise bitcoinin zirve yılı olup; euro ile arasında pozitif yönlü kuvvetli bir ilişki vardır (r=0.873; p<0.001). 2012-2020 döneminde istatistiksel olarak bitcoinin ham petrol fiyatı ile arasında negatif yönlü ve zayıf; cumhuriyet altını, altın ons fiyatı, dolar ve euro ile arasında ise kuvvetli bir ilişki vardır ve bu ilişki anlamlıdır. Yüksek hareketlilik, bitcoinin, istikrarlı bir ödeme aracından ziyade spekülatif bir yatırım aracı olarak görülmesi olarak algılanabilir. Bitcoinin uzun dönemde en çok euro ile arasında kuvvetli bir ilişki olduğu saptanmıştırİÇİNDEKİLER KABUL VE ONAY SAYFASI..............................................................................................iii BİLİMSEL ETİK BİLDİRİM SAYFASI...............................................................................iv ÖZET....................................................................................................................................... v ABSTRACT ...........................................................................................................................vi ÖNSÖZ..................................................................................................................................vii ŞEKİLLER DİZİNİ................................................................................................................. x TABLOLAR DİZİNİ..............................................................................................................xi EKLER ..................................................................................................................................xii KISALTMALAR DİZİNİ ....................................................................................................xiii GİRİŞ....................................................................................................................................... 1 1. BÖLÜM.............................................................................................................................. 3 1. BLOKZİNCİR TEKNOLOJİSİ........................................................................................... 3 1.1. Kriptoloji Kavramı....................................................................................................... 4 1.2. Blokzincir Çalışma Prensibi ........................................................................................ 6 1.2.1. HASH Fonksiyonları............................................................................................ 8 1.2.2. Eşler Arası Değer Değişim Sistemi ................................................................... 10 1.3. İşleyişteki Mekanizmalar........................................................................................... 14 1.3.1. Emek Kanıtı (Proof of Work) ............................................................................ 15 1.3.2. Hisse Kanıtı (Proof of Stake)............................................................................. 15 1.3.3. PoW ve PoS Karşılaştırması .............................................................................. 16 1.4. Sıfır Bilginin İspatı (Zero Knowledge Proof)............................................................ 18 1.5. Blokzincirin Sorun ve Sınırlamaları .......................................................................... 20 1.6. Herkes Yağmura Şiir Yazdı....................................................................................... 22 1.7. Blokzincir Teknolojisinin Kullanım Alanları............................................................ 23 1.8. Dünyada Blokzincir Atılımları .................................................................................. 26 ix 1.8.1. Kullanıldığı Sektörler......................................................................................... 27 1.8.2. Avrupa Birliği Blokzincir Gözlemevi................................................................ 29 1.9. Türkiye’de Blokzincir Atılımları............................................................................... 31 1.9.1. Tübitak Bilişim ve Bilgi Güvenliği İleri Teknolojiler Araştırma Merkezi........ 33 1.9.2. Blokzincir Çalıştayları ....................................................................................... 33 2. BÖLÜM............................................................................................................................ 36 2. KRİPTOPARALAR VE BITCOIN................................................................................... 36 2.1. Bitcoinin Geçmişi ...................................................................................................... 36 2.2. Bitcoin İşlem Süreci................................................................................................... 39 2.3. Güncel Haliyle Piyasalarda Bitcoin........................................................................... 44 2.4. Kripto Paraların Piyasadaki Yeri ............................................................................... 49 2.5. Libra........................................................................................................................... 51 2.6. Literatür Taraması...................................................................................................... 53 2.6.1. Akademik Çalışmalar......................................................................................... 53 2.6.2. Çalışmanın Literatürü ........................................................................................ 55 3. BÖLÜM............................................................................................................................ 58 3. UYGULAMA VE ANALİZ.............................................................................................. 58 3.1. Uygulamanın Amacı.................................................................................................. 58 3.2. Uygulamanın Kapsamı, Veri Seti ve Model.............................................................. 58 3.3. Metodoloji ve Yöntem............................................................................................... 59 3.4. Uygulama Bulguları................................................................................................... 60 4. SONUÇ ............................................................................................................................. 71 5. KAYNAKLAR................................................................................................................. 73 6. EKLER ............................................................................................................................. 81 ÖZGEÇMİŞ ......................................................................................................................... 8

Data trust framework using blockchain and smart contracts

Lack of trust is the main barrier preventing more widespread data sharing. The lack of transparent and reliable infrastructure for data sharing prevents many data owners from sharing their data. Data trust is a paradigm that facilitates data sharing by forcing data controllers to be transparent about the process of sharing and reusing data. Blockchain technology has the potential to present the essential properties for creating a practical and secure data trust framework by transforming current auditing practices and automatic enforcement of smart contracts logic without relying on intermediaries to establish trust. Blockchain holds an enormous potential to remove the barriers of traditional centralized applications and propose a distributed and transparent administration by employing the involved parties to maintain consensus on the ledger. Furthermore, smart contracts are a programmable component that provides blockchain with more flexible and powerful capabilities. Recent advances in blockchain platforms toward smart contracts' development have revealed the possibility of implementing blockchain-based applications in various domains, such as health care, supply chain and digital identity. This dissertation investigates the blockchain's potential to present a framework for data trust. It starts with a comprehensive study of smart contracts as the main component of blockchain for developing decentralized data trust. Interrelated, three decentralized applications that address data sharing and access control problems in various fields, including healthcare data sharing, business process, and physical access control system, have been developed and examined. In addition, a general-purpose application based on an attribute-based access control model is proposed that can provide trusted auditability required for data sharing and access control systems and, ultimately, a data trust framework. Besides auditing, the system presents a transparency level that both access requesters (data users) and resource owners (data controllers) can benefit from. The proposed solutions have been validated through a use case of independent digital libraries. It also provides a detailed performance analysis of the system implementation. The performance results have been compared based on different consensus mechanisms and databases, indicating the system's high throughput and low latency. Finally, this dissertation presents an end-to-end data trust framework based on blockchain technology. The proposed framework promotes data trustworthiness by assessing input datasets, effectively managing access control, and presenting data provenance and activity monitoring. A trust assessment model that examines the trustworthiness of input data sets and calculates the trust value is presented. The number of transaction validators is defined adaptively with the trust value. This research provides solutions for both data owners and data users’ by ensuring the trustworthiness and quality of the data at origin and transparent and secure usage of the data at the end. A comprehensive experimental study indicates the presented system effectively handles a large number of transactions with low latency

Exploring distributed collaboration and the potential of blockchain as an enabling technology

Since the emergence of the internet, the growth and development of communication technologies have presented new opportunities for collaboration. Practitioners in almost every industry can now collaborate with the skilled personnel across a range of fields, regardless of their geographic location. This contemporary working arrangement is referred to as Distributed Collaboration, which I define as the pursuit of a shared objective by groups that include non-proximate members, whose participation is facilitated by ICT. However, Distributed Collaboration is not without drawbacks. The dispersed and volatile nature of numerous participants makes these groups vulnerable to many challenges, primarily, free-riding, production blocking, evaluation apprehension, and perceptions of fairness. Meanwhile, Blockchain technology has emerged over the last decade, initially to facilitate the cryptocurrency market. However, research interest has recently focused on its potential to support non-financial use-cases such as the ability to track assets, both digital and physical, in a secure, transparent, and immutable manner. These technological capabilities of Blockchain would suggest it has the potential to support Distributed Collaboration by tracking individual contributions across a distributed ledger. Therefore, the objective of this thesis is to explore Distributed Collaboration and the potential of Blockchain as an enabling technology. This research was initiated by examining the potential of Blockchain to enable Distributed Collaboration from a macro-level perspective through the lens of the cryptocurrency market. The market can be considered a network of distributed participants, communicating to evaluate Blockchain as a technology. The findings show that in the absence of established factors and methods to evaluate cryptocurrencies, market participants rely on social cues to evaluate the assets. Next, I conducted a first iteration of Design Science Research (DSR) by exploring the potential for Blockchain to address the issue of free-riding in cross-functional groups. This endeavour found that there was potential. However, a more comprehensive understanding of the components of this research was required in order to extract theoretical and practical contributions. Therefore, a systematic literature review was performed to synthesise a comprehensive definition of Distributed Collaboration, as well as developing an understanding of the factors which lead to the success of these groups. Following this, qualitative interview data were gathered and analysed from practitioners operating in Distributed Collaboration to develop an understanding of the challenges faced when operating in this environment and the necessary components for a potential system to alleviate these issues. Finally, I completed a second iteration of DSR to rigorously investigate the potential of Blockchain to support Distributed Collaboration. A Blockchain-enabled system was developed, implementing the design construct of Creative Ancestry to improve perceptions of fairness in Distributed Collaboration. Findings show that Blockchain increases perceptions of fairness and thus improves overall collaboration. My research has implications for theory, practice, and future research. I provide a core model for successful Distributed Collaboration and detail how to implement a Blockchain-enabled system that addresses key issues. I also illustrate the presence of herding behaviour in the cryptocurrency market and how market participants are prone to amplified reactions to changes in the price of assets. These findings and their implications are discussed at length in the final chapter

A Generic Approach for the Automated Notarization of Cloud Configurations Using Blockchain-Based Trust.

Debido a su escalabilidad, las aplicaciones en la nube tienen una importante ventaja de costes para las empresas. En consecuencia, las empresas quieren tanto externalizar sus datos como obtener servicios de la nube. Sin embargo, dado que la mayoría de las empresas tienen políticas internas y requisitos de cumplimiento para operar y utilizar aplicaciones de software, el uso de aplicaciones en la nube crea un nuevo desafío para las empresas. La inclusión de aplicaciones en la nube equivale a la subcontratación de servicios en el sentido de que las empresas deben confiar en que el proveedor de aplicaciones en la nube aplicará los requisitos de cumplimiento interno en las aplicaciones adoptadas. La investigación ha demostrado que la confianza y el riesgo están estrechamente relacionados y son factores clave que influyen en la utilización de aplicaciones en la nube. Esta tesis pretende desarrollar una arquitectura en la nube que aborde este reto, trasladando la confianza en las configuraciones de cumplimiento del proveedor de aplicaciones en la nube a la cadena de bloques. Así, este trabajo pretende reducir el riesgo de adopción de las aplicaciones en la nube debido a los requisitos de cumplimiento. En esta tesis, la investigación de la ciencia del diseño se utiliza para crear la arquitectura para trasladar la confianza mencionada a la cadena de bloques. Un grupo de discusión determinó el alcance del trabajo. La base de conocimientos de este trabajo se construyó utilizando inteligencia artificial y una revisión sistemática de la literatura, y la arquitectura presentada se desarrolló y prototipó utilizando el método de desarrollo rápido de aplicaciones. Se utilizaron entrevistas guiadas semiestructuradas de método mixto para evaluar el enfoque de la arquitectura presentada y valorar las cualidades de reducción del riesgo de adopción. La tesis demostró que la arquitectura de software desarrollada podía trasladar la confianza del proveedor de la nube a la cadena de bloques. La evaluación de la arquitectura de software propuesta demostró además que el riesgo de adopción debido a las configuraciones de la nube basadas en el cumplimiento podía reducirse de "alto" a "bajo" utilizando la tecnología blockchain. Esta tesis presenta una arquitectura que desplaza la confianza para la implementación de configuraciones basadas en el cumplimiento de la normativa desde el proveedor de la nube a la cadena de bloques. Además, muestra que el cambio de confianza puede reducir significativamente el riesgo de adopción de las aplicaciones en la nube.Administración y Dirección de Empresa