1,720,997 research outputs found
Beveiligingsprimitieven voor softwaremodules die beschermd worden door geheugentoegangscontrole op basis van de programmateller
No full textOur society increasingly depends on computing devices. Customers rely on laptops and mobile devices to access security sensitive applications such as online banking. Companies have to protect their trade secrets. And governments have to guard their country's critical infrastructure against espionage and sabotage. Security of computing devices in such use cases is paramount and various security measures have been developed that raise the bar significantly for attackers. However, vulnerabilities in such systems still exist and are frequently exploited successfully. A common pitfall is that software security takes a layered approach where privileged layers keep getting extended with new components over the system's lifetime. This results in a snowball effect on the size of these privileged levels and this in turn increases the likelihood of software vulnerabilities. As all applications running on the device rely on the integrity of these layers, increasing the size of their code base has a negative impact on security of the overall device.Many security measures have been proposed to automatically harden the most privileged software layer, but they all fail to provide strong security guarantees. In this thesis, we considered a different approach. We developed three security primitives that can be applied at most privilege levels. Unlike related approaches, this set of primitives is fixed. Software components can be added easily at any privilege level, but no additional primitives will be required. Moreover, these security primitives can provide provable security guarantees.The most important security primitive is a program-counter-based access control mechanism. By enforcing different access rights on physical memory depending in which code module the processor is executing, sensitive parts of an application can be strongly isolated. For instance, a cryptographic key can be isolated to a protected module implementing a certificate-signing service.Since the key cannot be accessed by any other code than the module's, it cannot be stolen even if malware was already present on the platform. The access control mechanism also guarantees that the module is only accessible through the interface that it exposes explicitly.Second, we enable protected modules to limit which protected modules can access their services. Unrestricted access to modules may still allow a large range of attacks. While an attacker may no longer be able to access a well-isolated cryptographic key, for example, the exposed interface may still allow her to sign forged certificates. We prevent such attacks using a capability-based access control mechanism; a module can only be accessed if the caller ever received the capability to do so.Third, we propose a fast and practical state-continuity system. Using cryptographic properties, protected modules can use many services of the unprotected, legacy system while providing strong security guarantees. Unfortunately, these security guarantees only are ensured while the system is up and running. In practice systems crash, loose power or need to reboot. Integrity and confidentiality protecting the module's state before it is stored on disk is insufficient in such cases. Care must be taken that an attacker cannot present a stale state of a protected module as being fresh. Practical implementations are hindered by the substantial economical costs to add non-volatile storage to the processor. Many computing devices are already shipped with access-controlled non-volatile storage off-chip, but this memory is slow, very limited in size and wears out quickly. We propose an algorithm based on a simple hardware component to avoid all these shortcomings.During this dissertation we also focused on how these newly-added security primitives can be applied to provide strong security guarantees. A fully-abstract compilation scheme was developed that ensures that software-level abstractions provided to programmers cannot be broken; for every low-level attack, there also exists an attack at source-code level. This significantly simplifies reasoning about the security guarantees that protected modules provide and increases security of the overall system.status: Publishe
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The Heisenberg defense: proactively defending SGX enclaves against page-table-based side-channel attacks
No full textDispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Ariadne: A minimal approach to state continuity
No full textProtected-module architectures such as Intel SGX provide strong isolation guarantees to sensitive parts of applications while the system is up and running. Unfortunately systems in practice crash, go down for reboots or lose power at unexpected moments in time. To deal with such events, additional security measures need to be taken to guarantee that stateful modules will either recover their state from the last stored state, or fail-stop on detection of tampering with that state. More specifically, protected-module architectures need to provide a security primitive that guarantees that (1) attackers cannot present a stale state as being fresh (i.e. rollback protection), (2) once a module accepted a specific input, it will continue execution on that input or never advance, and (3) an unexpected loss of power must never leave the system in a state from which it can never resume execution (i.e. liveness guarantee).
We propose Ariadne, a solution to the state-continuity problem that achieves the theoretical lower limit of requiring only a single bit flip of on-volatile memory per state update. Ariadne can be easily adapted to the platform at hand. In low-end devices where non-volatile memory may wear out quickly and the bill of materials (BOM) needs to be minimized, Ariadne can take optimal use of non-volatile memory. On SGX-enabled processors, Ariadne can be readily deployed to protect stateful modules (e.g., as used by Haven and VC^3).status: Publishe
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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