14,636 research outputs found

    Systemization of Pluggable Transports for Censorship Resistance

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    An increasing number of countries implement Internet censorship at different scales and for a variety of reasons. In particular, the link between the censored client and entry point to the uncensored network is a frequent target of censorship due to the ease with which a nation-state censor can control it. A number of censorship resistance systems have been developed thus far to help circumvent blocking on this link, which we refer to as link circumvention systems (LCs). The variety and profusion of attack vectors available to a censor has led to an arms race, leading to a dramatic speed of evolution of LCs. Despite their inherent complexity and the breadth of work in this area, there is no systematic way to evaluate link circumvention systems and compare them against each other. In this paper, we (i) sketch an attack model to comprehensively explore a censor's capabilities, (ii) present an abstract model of a LC, a system that helps a censored client communicate with a server over the Internet while resisting censorship, (iii) describe an evaluation stack that underscores a layered approach to evaluate LCs, and (iv) systemize and evaluate existing censorship resistance systems that provide link circumvention. We highlight open challenges in the evaluation and development of LCs and discuss possible mitigations.Comment: Content from this paper was published in Proceedings on Privacy Enhancing Technologies (PoPETS), Volume 2016, Issue 4 (July 2016) as "SoK: Making Sense of Censorship Resistance Systems" by Sheharbano Khattak, Tariq Elahi, Laurent Simon, Colleen M. Swanson, Steven J. Murdoch and Ian Goldberg (DOI 10.1515/popets-2016-0028

    Income Shocks, Mortgage Repayment Risk and Financial Distress Among UK Households

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    This paper examines the prevalence of mortgage arrears in the U.K using the British Household Panel Survey (BHPS). The majority of reported problems occur in the first few years after purchase. Episodes of unemployment, long-term sickness or relationship breakdown all predict repayment difficulties, as well as measures of leverage and income gearing at the point of origination. Using proxy measures for unemployment risk, ill-health risk and separation risk at the time of purchase, constructed from a variety of instruments, repayment difficulties are shown to be strongly correlated with ex ante repayment risk. This result raises questions about the efficiency of the mortgage lending process and the possibility that a significant proportion of mortgage arrears and defaults could be prevented by improved screening of repayment risk at the time of application.

    Leveraging upon standards to build the Internet of things

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    Smart embedded objects will become an important part of what is called the Internet of Things. However, the integration of embedded devices into the Internet introduces several challenges, since many of the existing Internet technologies and protocols were not designed for this class of devices. In the past few years, there were many efforts to enable the extension of Internet technologies to constrained devices. Initially, this resulted in proprietary protocols and architectures. Later, the integration of constrained devices into the Internet was embraced by IETF, moving towards standardized IP-based protocols. Long time, most efforts were focusing on the networking layer. More recently, the IETF CoRE working group started working on an embedded counterpart of HTTP, allowing the integration of constrained devices into existing service networks. In this paper, we will briefly review the history of integrating constrained devices into the Internet, with a prime focus on the IETF standardization work in the ROLL and CoRE working groups. This is further complemented with some research results that illustrate how these novel technologies can be extended or used to tackle other problems.The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2 007-2013) under grant agreement n°258885 (SPITFIRE project), from the iMinds ICON projects GreenWeCan and O’CareCloudS, and a VLI R PhD scholarship to Isam Ishaq

    Does the Investment Opportunities Bias Affect the Investment-Cash Flow Sensitivities of Unlisted SMEs?

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    Using a panel of 5,999 small and medium-sized Belgian enterprises (SMEs) over the period 2002-2008, we identify three measures of investment opportunities suitable for unlisted firms. We then estimate firm-varying investment-cash flow sensitivities (ICFS) from reduced-form investment equations that include these measures, and compare them with those derived from a model that does not control for investment opportunities. We find that all our models yield similar ICFS estimates, which are significantly related to a wide set of proxies for financing constraints. These findings suggest that the ICFS of SMEs do not simply reflect investment opportunities. The investment opportunities bias may therefore have been overstated in previous literature.Financing constraints, Firm-varying investment-cash flow sensitivities, Investment opportunities, Gross added value.

    Likelihood-based inference for correlated diffusions

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    We address the problem of likelihood based inference for correlated diffusion processes using Markov chain Monte Carlo (MCMC) techniques. Such a task presents two interesting problems. First, the construction of the MCMC scheme should ensure that the correlation coefficients are updated subject to the positive definite constraints of the diffusion matrix. Second, a diffusion may only be observed at a finite set of points and the marginal likelihood for the parameters based on these observations is generally not available. We overcome the first issue by using the Cholesky factorisation on the diffusion matrix. To deal with the likelihood unavailability, we generalise the data augmentation framework of Roberts and Stramer (2001 Biometrika 88(3):603-621) to d-dimensional correlated diffusions including multivariate stochastic volatility models. Our methodology is illustrated through simulation based experiments and with daily EUR /USD, GBP/USD rates together with their implied volatilities

    Housing Wealth and Household Indebtedness: Is there a Household 'Financial Accelerator'?

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    The 'financial accelerator' model when applied to households states that shocks to household balance sheets (primarily changes in house prices) amplify fluctuations in consumer spending by tightening or relaxing collateral constraints on borrowing. We construct an alternative model where households also have access to unsecured debt, and examine the effect of shocks to house prices on debt-financed consumption in this augmented setting. Our alternative model reduces the amplitude of fluctuations in debt-financed consumer spending arising from fluctuations in household asset values. The paper tests the applicability of the two models using panel data for the United Kingdom that allow us to measure collateral constraints, changes in asset values and financial indebtedness at the household level.Collateral, consumer spending, Housing wealth, unsecured debt.

    A new proxy of social capital and the economic performance across the Italian regions

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    In the last 20 years, social capital, has been evoked in several field of social science research and used to explain a vast range of phenomena: political participation, institution performance, corruption, economic success of countries and so on. Unfortunately, dealing with social capital at a scientific level presents, at least, three main problems. First social capital’s definition is still elusive, especially due to its multi-dimensional nature. Second, it is a particular form of capital related to a very high level of intangibility. Finally, because of lack of suitable data there is neither a universal measurement method, nor a single underlined indicator commonly accepted by the literature. These are some of the reasons for which social capital measures are considered as proxies. By using the density of workers within industrial districts, we have constructed an alternative proxy to those that already exist in the literature in order to empirically analyse the difference, in terms of economic performance, across the Italian regions. The methodology we have applied to derive the index is identical to that one used to construct the Putnam’s instrument. Empirical evidence shows that our measure does not affect macroeconomic indicators such as investment and income per capita. However, it significantly influences unemployment disparities, and the level of innovation
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