A Security Infrastructure for Mobile Transactional Systems

In this paper, we present an infrastructure for providing secure transactional replication support for peer-to-peer, decentralized databases. We first describe how to effectively provide protection against external threats, malicious actions by servers not authorized to access data, using conventional cryp-tography-based mechanisms. We then classify and present algorithms that provide protection against internal threats, malicious actions by authenticated servers that misrepresent protocol-specific infor-mation. Our approach to handling internal threats uses both cryptographic techniques and modifica-tions to the update commit criteria. The techniques we propose are unique in that they not only enable a tradeoff between performance and the degree of tolerance to malicious servers, but also allow for indi-vidual servers to support non-uniform degrees of tolerance without adversely affecting the performance of the rest of the system. We investigate the cost of our security mechanisms in the context of Deno: a prototype object replica-tion system designed for use in mobile and weakly-connected environments. Experimental results reveal that protecting against internal threats comes at a cost, but the marginal cost for protecting against larger cliques of malicious insiders is generally low. Furthermore, comparison with a decentralized Read-One Write-All protocol shows that our approach performs significantly better under various workloads. (Also cross-referenced as UMIACS-TR-2000-59

Optimistic replication

Data replication is a key technology in distributed data sharing systems, enabling higher availability and performance. This paper surveys optimistic replication algorithms that allow replica contents to diverge in the short term, in order to support concurrent work practices and to tolerate failures in low-quality communication links. The importance of such techniques is increasing as collaboration through wide-area and mobile networks becomes popular. Optimistic replication techniques are different from traditional “pessimistic ” ones. Instead of synchronous replica coordination, an optimistic algorithm propagates changes in the background, discovers conflicts after they happen and reaches agreement on the final contents incrementally. We explore the solution space for optimistic replication algorithms. This paper identifies key challenges facing optimistic replication systems — ordering operations, detecting and resolving conflicts, propagating changes efficiently, and bounding replica divergence — and provides a comprehensive survey of techniques developed for addressing these challenges

Weathering a Medieval Climate: Gauging the impact of natural hazards on northern European society through archaeology and history, AD 1000-1550

This thesis investigates the occurrence of meteorological hazards in northern Europe and their impact on society during the medieval period (AD 1000-1550). When high-magnitude meteorological hazards affected vulnerable human populations disasters were the inevitable consequence. These events resulted in highly complex repercussions over the short- and long- terms, touching a wide variety of different spheres of human activity and experience. Additionally, the occurrence of these events was usually sudden and unpredictable in an age when natural processes were poorly understood. As a result, floods, storms and other hazards were widely interpreted through a framework of religious and superstitious beliefs which is widely attested by the historical record. A range of different types of archaeological artefact are also associated with these beliefs and, particularly, in accruing personal protection from a hazardous environment. At the same time, medieval society understood disasters in a practical sense and took steps to minimise risk through constructing flood defences and reinforcing structures damaged by storms. Medieval society, therefore, interpreted disasters through a duality of understanding in which disasters could be the result of spiritual or superstitious causes but could be mitigated through established and well-understood practical solutions. This thesis evaluates this duality in reference to specific case studies and in light of the significant demographic and climatic fluctuations of the medieval period—as a result of the Black Death and the transition to the Little Ice Age

A Consultation on Higher Education in Africa

Reviews universities in English-speaking countries in sub-Saharan Africa. Includes results of meetings with university leaders, government officials, researchers, teachers, students, and donor agency representatives in Africa, Europe, and North America

Our Central Banking System - A Lesson in Money Management

The purpose of this study is to set forth some of the fundamental principles of the American Banking System in their relationship to the changing progress of other American businesses. In this study an attempt has been made to organize the materials at hand in such a manner as to give the reader a clear understanding of how the system is set up, how it is organized, and how it is controlled. Stress has been placed chiefly on what is termed the Federal Reserve System and its function in the American economy. The problems, including questions to which answers must be sought were as follows: 1. What influence did banks in England have upon the Central Banking System of America? 2. How did the State Bank Growth in the United States after 1816 renovate the American Banking System after the failure of the First and Second Banks of the United States? 3. What were the conditions existing under the State Bank era that led Congress to enact the National Bank Act in 1863? 4. What were the existing conditions under the National Banking System that gave rise to the Federal Reserve System? 5. How did the operation of the Federal Reserve System become a lesson in Money Management

The Future of Financial Systems in the Digital Age

This book is open access, which means that you have free and unlimited access. The increasing capacity of digital networks and computing power, together with the resulting connectivity and availability of “big data”, are impacting financial systems worldwide with rapidly advancing deep-learning algorithms and distributed ledger technologies. They transform the structure and performance of financial markets, the service proposition of financial products, the organization of payment systems, the business models of banks, insurance companies and other financial service providers, as well as the design of money supply regimes and central banking. This book, The Future of Financial Systems in the Digital Age: Perspectives from Europe and Japan,brings together leading scholars, policymakers, and regulators from Japan and Europe, all with a profound and long professional background in the field of finance, to analyze the digital transformation of the financial system. The authors analyze the impact of digitalization on the financial system from different perspectives such as transaction costs and with regard to specific topics like the potential of digital and blockchain-based currency systems, the role of algorithmic trading, obstacles in the use of cashless payments, the challenges of regulatory oversight, and the transformation of banking business models. The collection of chapters offers insights from Japanese and European discourses, approaches, and experiences on a topic otherwise dominated by studies about developments in the USA and China

Resource partitioning in colonial herons, with particular reference to the grey heron Ardea cinerea L. and the pu rple heron Ardea Purpurea L., in the Camargue, S. France

There have been major changes in the relative abundance of the six species of colonial Ardeidae (herons and egrets) which breed in the Camargue, since I9680 Two species, the Grey Heron and the Cattle Egret, started nesting in the delta in the mid-sixties and have increased dramatically in numbers, whilst there has been a simultaneous decline in the breeding population of Purple Herons. Examination of counts and of the patterns of resource use by these species show that although Grey and Purple Herons overlap extensively in morphology, breeding sites (reedbeds), feeding sites and diet, competition during the breeding season cannot have been responsible for the observed changes, since numbers of Purples have remained stable in those areas where the greatest increases of Greys have occurred, whilst they have completely disappeared in some areas where there were no Greys. Instead, breeding sites have been destroyed to such an extent within the delta that they now limit the number of Purple Herons below the level set by winter mortality, which has been shown to limit breeding populations in other areas. For Purple Herons, the relationship between colony size and food resources was examined at a breeding-site where colony size was not limited by the availability of adequate breeding habitat. Adults exploited feeding areas near (<2km) to the colony in preference to those further away (max. 15km); near areas were the first to be filled and remained filled throughout the breeding season. Early breeders held feeding territories in areas adjacent to the colony, to the exclusion of later breeders. Breeding partners did not share the same feeding territories, nor associate in any way on the feeding areas. It is suggested that the increasing costs of flight-time and flight-energy incurred by adults foraging further from the colony may set an upper limit to colony size. Aspects of the breeding biology of the Purple Heron are described. The average clutch-size in the Camargue is the lowest reported for Europe, and declined significantly through the summer. Siblings differed considerably in size as a result of the asynchronous hatching of the clutch, and not of egg-size differences. The first two chicks in broods of three, and the first three chicks in broods of four, grew fastest and a high proportion of the youngest chicks in a brood died of starvation. It is argued that the number of young fledged is limited by the ability of the adults to deliver food to the nest. Changes in clutch-size are used to adjust brood-size to predictable changes in food availability, while brood reduction through sibling hierarchies provides a fine tuning at the time of peak nestling demand. The diet of Grey and Purple Herons was examined from nestling regurgitations; both species are highly piscivorous. The Grey Heron specialises on large Eels, Carp and Mullet whilst the Purple Heron takes Eels and a wide variety of other fish, plus some invertebrates. Mechanisms of prey selection were examined for the Grey Heron. Large Carp and similar fish are the most profitable prey for adults whilst small fish and species which possess protective spines, such as Catfish, are of low profitability. Young chicks cannot consume prey as large as can the adults, although this ability develops by the time they are ca 30 days old. Evidence is presented that adults select prey in relation to the age of their chicks. The results of this study are discussed in relation to the conservation of breeding heron populations in Europe. Recommendations for the management of breeding areas are proposed

Secrets Revealed in Container Images: An Internet-wide Study on Occurrence and Impact

Containerization allows bundling applications and their dependencies into a single image. The containerization framework Docker eases the use of this concept and enables sharing images publicly, gaining high momentum. However, it can lead to users creating and sharing images that include private keys or API secrets-either by mistake or out of negligence. This leakage impairs the creator's security and that of everyone using the image. Yet, the extent of this practice and how to counteract it remains unclear. In this paper, we analyze 337,171 images from Docker Hub and 8,076 other private registries unveiling that 8.5% of images indeed include secrets. Specifically, we find 52,107 private keys and 3,158 leaked API secrets, both opening a large attack surface, i.e., putting authentication and confidentiality of privacy-sensitive data at stake and even allow active attacks. We further document that those leaked keys are used in the wild: While we discovered 1,060 certificates relying on compromised keys being issued by public certificate authorities, based on further active Internet measurements, we find 275,269 TLS and SSH hosts using leaked private keys for authentication. To counteract this issue, we discuss how our methodology can be used to prevent secret leakage and reuse.Comment: 15 pages, 7 figure

Market-based Instruments for Environmental Policymaking in Latin America and the Caribbean: Lessons from Eleven Countries

This report is a summary of country studies in Latin America and the Caribbean, addressing the use of market-based instruments (MBIs) and command-and-control (CAC) measures for environmental management in the region. Even though MBIs can significantly add efficiency to existing CAC mechanisms, the scope of MBIs should match the countries institutional capacity to implement them. Gradual and flexible reforms are likely to succeed within the current regional context of continued institutional changes. A key function of MBIs is usually revenue collection, though it does not necessarily lead to successful environmental management. The study suggests that revenues should be channeled to local authorities for an effective MBI's implementation. The report also critiques the regular practice of international donor agencies in recommending the solutions suitable for developed countries, without considering the institutional conditions in developing countries. Further, the study explores both the successes and difficulties experienced in the region regarding regulations, macro-policies, and MBIs; the institutional frameworks of the countries under review; and, the issues considered in the design of MBIs, in order to promote a beneficial dialogue among them