The problem of records retention is often viewed as simply deleting records when they have outlived their purpose. However, in the world of relational databases there is no standardized notion of a business record and its retention obligations. Unlike physical documents such as forms and reports, information in databases is organized such that one item of data may be part of various legal records and consequently subject to several (and possibly conflicting) retention policies. This thesis proposes a framework for records retention in relational database systems. It presents a mechanism through which users can specify a broad range of protective and destructive data retention policies for relational records. Compared to naïve solutions for enforcing records management policies, our framework is not only significantly more efficient but it also addresses several unanswered questions about how policies can be mapped from given legal requirements to actions on relational data. The novelty in our approach is that we defined a record in a relational database as an arbitrary logical view, effectively allowing us to reduce several challenges in enforcing data retention policies to well-studied problems in database theory. We argue that our expression based approach of tracking records management obligations is not only easier for records managers to use but also far more space/time efficient compared to traditional metadata approaches discussed in the literature. The thesis concludes with a thorough examination of the limitations of the proposed framework and suggestion for future research in the area of records management for relational database management systems.

The problem of records retention is often viewed as simply deleting records when they have outlived their purpose. However, in the world of relational databases there is no standardized notion of a business record and its retention obligations. Unlike physical documents such as forms and reports, information in databases is organized such that one item of data may be part of various legal records and consequently subject to several (and possibly conflicting) retention policies. This thesis proposes a framework for records retention in relational database systems. It presents a mechanism through which users can specify a broad range of protective and destructive data retention policies for relational records. Compared to naïve solutions for enforcing records management policies, our framework is not only significantly more efficient but it also addresses several unanswered questions about how policies can be mapped from given legal requirements to actions on relational data. The novelty in our approach is that we defined a record in a relational database as an arbitrary logical view, effectively allowing us to reduce several challenges in enforcing data retention policies to well-studied problems in database theory. We argue that our expression based approach of tracking records management obligations is not only easier for records managers to use but also far more space/time efficient compared to traditional metadata approaches discussed in the literature. The thesis concludes with a thorough examination of the limitations of the proposed framework and suggestion for future research in the area of records management for relational database management systems.

This thesis analyzes legal framework as well as other issues regarding monitoring and intercepting the substance of communication under Section 88 of the Criminal Procedure Act. Also, the characteristics of logging and accessing data relating to communication (such as times, patterns, locations and parties involved) under Section 88a are described. These institutes in certain instances represent lawful interfere with the right to respect for private life and other human rights and both are of critical importance in the investigation of many types of crimes. The thesis is systematically divided into seven chapters. Chapter One presents both concepts in their relationship to the affected basic human rights and describes characteristics, major principles as well as the procedure of issuing a wiretap and data retention warrants. As both concepts have similar features with conception of Surveillance of persons and items under the Section 158d of the Czech Criminal Procedure Act, comparison with this institute is provided in the second chapter. The third Chapter is devoted to the evolution of Wiretapping legislation and its changes due to particular amendments. The first legal regulation of Wiretapping was adopted in the Czech Criminal Procedure Act in 1991 as a response to the political revolution...

Companies that perform data backup lose valuable data because they lack reliable data backup or restoration methods. The purpose of this study was to examine the need for a Six Sigma data backup performance indicator tool that clarifies the current state of a data backup method using an intuitive numerical scale. The theoretical framework for the study included backup theory, disaster recovery theory, and Six Sigma theory. The independent variables were implementation of data backup, data backup quality, and data backup confidence. The dependent variable was the need for a data backup performance indicator. An adapted survey instrument that measured an organization's data backup plan, originally administered by Information Week, was used to survey 107 businesses with 15 to 250 employees in the Greater Cincinnati area. The results revealed that 69 out of 107 small businesses did not need a data backup performance indicator and the binary logistic regression model indicated no significant relationship between the dependent and independent variables. The conclusion of the study is that many small businesses have not experienced a disaster and cannot see the importance of a data backup indicator that quantifies recovery potential in case of a disaster. It is recommended that further research is required to determine if this phenomenon is only applicable only to small businesses in the Greater Cincinnati area through comparisons based on business size and location. This study contributes to positive social change through improvement of data backup, which enables organizations to quickly recover from a disaster, thereby saving jobs and contributing to the stability of city, state, and national economies.

In this thesis, we propose a novel vertical MOSFET device with middle partial insulator (MPI) or VMPI for capacitorless one transistor dynamic random access memory (1T-DRAM) application. In TCAD simulations, we compare the device performances of the planar MPI, conventional silicon-on-insulator SOI, and our proposed VMPI. Based on numerical simulation, we find out that the VMPI device has a large kink phenomenon for improving the programming window. As far as the data retention time is concerned, the hole carriers leaking into the source region are reduced due to the presence of a large pseudo neutral region and an effective blocking oxide layer. The retention time can thus be improved about 5 times when compared with conventional SOI counterpart. Furthermore, it should be noted that the gate-all-around (GAA) VMPI device structure not only increases the body pseudo-neutral region, but also enhances the 1T-DRAM performances, suggesting that the proposed VMPI can become a candidate for 1T-DRAM application.

The ongoing fast pace research in hardware and software technology has resulted in memory devices efficient and faster than ever before. However, the issue of security of the contained data is rarely discussed. There is an evident capability of these devices to retain data even when it is erased. In this thesis, a study is conducted to qualitatively analyze the extent to which data deletion is important and why secure deletion should be applied. Afterwards, following the sequential exploratory procedure, this paper presents an analysis of methods used to recover the data after being deleted in addition to the techniques used to securely delete this data. Based on this study, some recommendations are made to ensure the safety of data.

Social media data is used for analytics, e.g., in science, authorities or the industry. Privacy is often considered a secondary problem. However, protecting the privacy of social media users is demanded by laws and ethics. In order to prevent subsequent abuse, theft or public exposure of collected datasets, privacy-aware data processing is crucial. This dissertation presents a concept to process social media data with social media user’s privacy in mind. It features a data storage concept based on the cardinality estimator HyperLogLog to store social media data, so that it is not possible to extract individual items from it, but only to estimate the cardinality of items within a certain set, plus running set operations over multiple sets to extend analytical ranges. Applying this method requires to define the scope of the result before even gathering the data. This prevents the data from being misused for other purposes at a later point in time and thus follows the privacy by design principles. This work further shows methods to increase privacy through the implementation of abstraction layers. An included case study demonstrates the presented methods to be suitable for application in the field.:1 Introduction 1.1 Problem 1.2 Research objectives 1.3 Document structure 2 Related work 2.1 The notion of privacy 2.2 Privacy by design 2.3 Differential privacy 2.4 Geoprivacy 2.5 Probabilistic Data Structures 3 Concept and methods 3.1 Collateral data 3.2 Disposable data 3.3 Cardinality estimation 3.4 Data precision 3.5 Extendability 3.6 Abstraction 3.7 Time consideration 4 Summary of publications 4.1 HyperLogLog Introduction 4.2 VOST Case Study 4.3 Real-time Streaming 4.4 Abstraction Layers 4.5 VGIscience Book Chapter 4.6 Supplementary Software Materials 5 Discussion 5.1 Prevent accidental data disclosure 5.2 Feasibility in the field 5.3 Adjustability for different use cases 5.4 Limitations of HLL 5.5 Security 5.6 Outlook and further research 6 Conclusion Appendix References Publications

DP - Lukáš Jirovský, Data retention, 2015 Abstract Data retention - storing of traffic and location metadata The topic of this thesis is data retention - traffic and location metadata storing (and providing to state) by telecommunication providers according to Czech and European law (including rulings of constitutional courts). It also describes compliance or conflict with the users right to privacy and also possibilities to provide this data to users. There is also technical description of the data with their meaning and statistics of crimes detection according to validity of this law.

De nos jours, les nouvelles technologies ne cessent d'évoluer et de former une partie intégrante dans la vie quotidienne de chacun. Ces dernières profitent du développement de systèmes électroniques complexes qui nécessitent l'utilisation de composants mémoires de plus en plus performants et présentant de grandes capacités de stockage. Ainsi, dans cette course à la miniaturisation, la technologie Flash jusqu'ici prépondérante sur le marché des mémoires non volatiles laisse aujourd'hui entrevoir ses limites. En conséquence, différentes mémoires émergentes résistives sont développées et parmi celles-ci se trouvent les mémoires à changement de phase PCRAM qui présentent un grand intérêt dans le monde des mémoires non volatiles grâce à leur bonne capacité de réduction d'échelle ainsi que leur coût réduit par rapport aux mémoires Flash. Cependant, pour être compétitives face aux autres technologies et pour prétendre à des applications embarquées, elles doivent répondre à plusieurs challenges tels que réduire leur courant de programmation, augmenter leur vitesse de programmation et améliorer leur stabilité thermique. Pour cela, différentes voies sont explorées dans la littérature, notamment l'utilisation d'architectures innovantes ou de matériaux à changement de phase alternatifs. Dans cette thèse, nous nous sommes intéressés à l'investigation des mécanismes de défaillance qui affectent la stabilité thermique et temporelle des mémoires à changement de phase, plus précisément la rétention de l'état RESET et la stabilité des états programmés affectée par le phénomène de « drift ». Le développement de matériaux alternatifs utilisant une stoechiométrie optimisée ou incorporant un dopage nous permet d'obtenir des dispositifs performants d'un point de vue électrique et présentant des propriétés de rétention satisfaisant les spécifications des applications embarquées en particulier l'automobile. De plus, grâce au développement d'une nouvelle procédure de pré-codage, ces dispositifs permettent de conserver les données préprogrammées sur la puce mémoire au cours de l'étape de soudure de cette dernière sur le circuit électronique. Ils constituent une solution prometteuse pour les applications de cartes sécurisées. Enfin, nous avons proposé une procédure de programmation optimisée qui permet de diminuer l'effet du drift de la résistance de l'état SET observé pour les matériaux alternatifs. Ensuite, nous avons montré via des mesures de bruit à basses fréquences que cet effet est dû à la relaxation structurale des zones amorphes présentes dans ces matériaux actifs. De plus, nous avons mis en évidence pour la première fois la diminution du bruit normalisé de l'état SET ainsi que l'influence majeure des défauts d'interfaces sur le bruit à basses fréquences de cet état. / Nowadays, new technologies are rising steadily and forming an integral part in the daily lives of everyone. They take advantage of the development of electronic systems for which the complexity requires the use of memory devices more and more efficient and with large storage capacities. Because of some performance degradation, the scaling of Flash technology who was so far predominant in the non-volatile memories market, is today reaching its limits. As a result, different emerging resistive memories are being developed. Among them, the phase-change memory technology PCRAM is very attractive because of its non-volatility, scalability, as well as reduced cost compared to standard Flash. Nevertheless, to compete with other technologies and to address the embedded applications market, PCRAM still face some challenges, such as decreasing the programming current densities, increasing the programming speed and increasing the thermal stability of the two memory states. For that purpose, different solutions have been tried in the literature, including using new device architectures and optimized phase-change materials. In this work, we are interested in investigating the failure mechanisms that affect thermal and temporal stability of phase change memories, in particular the retention of the RESET state and the stability of the programmed states disturbed by the drift phenomenon. The development of alternative materials using an optimized stoichiometry or incorporating doping allows us to achieve high electrical performance devices and to reach the required retention properties of embedded applications and particularly the automotive one. Moreover, thanks to the development of a new pre-coding procedure, these devices allow to keep stable the preprogrammed data on the memory chip during the soldering step of the latter on the electronic circuit. They represent a promising solution for Smart-Card applications. Finally, we have proposed an optimized programming procedure which enables to reduce the drift effect of the resistance of the SET state observed for optimized materials. This drift phenomenon was investigated by using low frequency noise measurements. Therefore, we have shown that this effect is due to the structural relaxation of amorphous parts in the active material. Besides, we highlighted for the first time the major influence of interface defects on the low-frequency noise of this state.

Dans cette thèse, nous proposons une étude détaillée des mécanismes responsables de la perte de données dans les mémoires à changement de phase enrichies en germanium (Ge-rich PRAMs), à savoir la dérive de la résistance au cours du temps et la recristallisation de la phase amorphe. Nous commençons par une présentation du contexte dans lequel s'inscrit cette étude an donnant un aperçu rapide du marché des mémoires à semiconducteur et une comparaison des mémoires non volatiles émergentes. Les principes de fonctionnement de la technologie PRAM sont introduits, avec ses avantages, ses inconvénients, ainsi que la physique régissant le processus de cristallisation dans les matériaux à changement de phase, avant de décrire les problèmes de fiabilité qui nous intéressent.Une caractérisation électrique complète de dispositifs intégrant des alliages de GST enrichi en germanium est ensuite proposée, en commençant par la caractérisation des matériaux utilisés dans nos cellules, introduisant alors les avantages des alliages enrichis en Ge sur le GST standard. Les performances électriques des dispositifs intégrant ces matériaux sont analysées, avec une étude statistique des caractéristiques SET & RESET, de la fenêtre de programmation, de l'endurance et de la vitesse de cristallisation. Nous nous concentrons ensuite sur le thème principal de cette thèse en analysant la dérive en résistance de l'état SET de nos dispositifs Ge-rich, ainsi que les performances de rétention de l'état RESET.Dans la dernière partie, nous étudions les mécanismes physiques impliqués dans ces phénomènes en fournissant une étude détaillée de la structure des cellules, grâce à l'utilisation de la Microscopie Électronique en Transmission (MET). Les conditions et configurations expérimentales sont décrites, avant de présenter les résultats qui nous ont permis d'aller plus loin dans la compréhension de la dérive en résistance et de la recristallisation de la phase amorphe dans les dispositifs Ge-rich. Une discussion est finalement proposée, reliant les résultats des caractérisations électriques avec ceux des analyses TEM, conduisant à de nouvelles perspectives pour l'optimisation des dispositifs PRAMs. / In this thesis we provide a detailed study of the mechanisms responsible for data loss in Ge-rich Ge2Sb2Te5 Phase-Change Memories, namely resistance drift over time and recrystallization of the amorphous phase. The context of this work is first presented with a rapid overview of the semiconductor memory market and a comparison of emerging non-volatile memories. The working principles of PRAM technology are introduced, together with its advantages, its drawbacks, and the physics governing the crystallization process in phase-change materials, before describing the reliability issues in which we are interested.A full electrical characterization of devices integrating germanium-enriched GST alloys is then proposed, starting with the characterization of the materials used in our PCM cells and introducing the benefits of Ge-rich GST alloys over standard GST. The electrical performances of devices integrating those materials are analyzed, with a statistical study of the SET & RESET characteristics, programming window, endurance and crystallization speed. We then focus on the main topic of this thesis by analyzing the resistance drift of the SET state of our Ge-rich devices, as well as the retention performances of the RESET state.In the last part, we investigate on the physical mechanisms involved in these phenomena by providing a detailed study of the cells' structure, thanks to Transmission Electron Microscopy (TEM). The experimental conditions and setups are described before presenting the results which allowed us to go deeper into the comprehension of the resistance drift and the recrystallization of the amorphous phase in Ge-rich devices. A discussion is finally proposed, linking the results of the electrical characterizations with the TEM analyses, leading to new perspectives for the optimization of PRAM devices.