1,720,960 research outputs found
Efficient security analysis of administrative access control policies
Full text linkIn recent years access control has been a crucial aspect of computer systems, since it is the component responsible for giving users specific permissions enforcing a administrator-defined policy. This lead to the formation of a wide literature proposing and implementing access control models reflecting different system perspectives. Moreover, many analysis techniques have been developed with special attention to scalability, since many security properties have been proved hard to verify. In this setting the presented work provides two main contributions.
In the first, we study the security of workflow systems built on top of an attribute-based access control in the case of collusion of multiples users. We define a formal model for an ARBAC based workflow system and we state a notion of security against collusion. Furthermore we propose a scalable static analysis technique for proving the security of a workflow. Finally we implement it in a prototype tool showing its effectiveness.
In the second contribution, we propose a new model of administrative attribute-based access control (AABAC) where administrative actions are enabled by boolean expressions predicating on user attributes values. Subsequently we introduce two static analysis techniques for the verification of reachability problem: one precise, but bounded, and one over-approximated. We also give a set of pruning rules in order to reduce the size of the problem increasing scalability of the analysis. Finally, we implement the analysis in a tool and we show its effectiveness on several realistic case studies
Static detection of collusion attacks in ARBAC-based workflow systems
No full textAuthorization in workflow systems is usually built on top of role-based access control (RBAC), security policies on workflows are then expressed as constraints on the users performing a set of tasks and the roles assigned to them. Unfortunately, when role administration is distributed and potentially untrusted users contribute to the role assignment process, like in the case of Administrative RBAC (ARBAC), collusions may take place to circumvent the intended workflow security policies. In a collusion attack, a set of users of a workflow system collaborates by changing the user-to-role assignment, so as to sidestep the security policies and run up to completion a workflow they could not complete otherwise. In this paper, we study the problem of collusion attacks in a formal model of workflows based on stable event structures and we define a precise notion of security against collusion. We then propose a static analysis technique based on a reduction to a role reachability problem for ARBAC, which can be used to prove or disprove security for a large class of workflow systems. We also discuss how to aggressively optimise the obtained role reachability problem to ensure its tractability. Finally, we implement our analysis in a tool, WARBAC, and we experimentally show its effectiveness on a set of publicly available examples, including a realistic case study
WEIGHTED PARTIAL MATCHING UNDER HOMOMORPHIC ENCRYPTION
No full textVarious embodiments are provided for performing weighted partial matching under homomorphic encryption in a computing environment. Selected data may be encoded and encrypted into an encrypted query for comparison using private set intersection (PSI) under homomorphic encryption (HE). An encrypted score may be determined according to data blocks of the selected data and a set of weights for each of the data blocks of the selected data to identify matches between the data and the encrypted query. The encrypted score may be decrypted and decoded to identify matches between the encrypted query with the selected data
Fine-grained Detection of Privilege Escalation Attacks on Browser Extensions
Full text linkEven though their architecture relies on robust security principles, it is well-known that poor programming practices may expose browser extensions to serious security flaws, leading to privilege escalations by untrusted web pages or compromised extension components. We propose a formal security analysis of browser extensions in terms of a fine-grained characterization of the privileges that an active opponent may escalate through the message passing interface and we discuss to which extent current programming practices take this threat into account. Our theory builds on a formal language that embodies the essential features of JavaScript, together with few additional constructs dealing with the security aspects specific to the browser extension architecture. We then present a flow logic specification estimating the safety of browser extensions modeled in our language against the threats of privilege escalation and we prove its soundness. Finally, we show the feasibility of our approach by means of Chen, a prototype static analyzer for Google Chrome extensions based on our flow logic specification
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
SMT-Based Refutation of Spurious Bug Reports in the Clang Static Analyzer
Full text linkWe describe and evaluate a bug refutation extension for the Clang Static Analyzer (CSA) that addresses the limitations of the existing built-in constraint solver. In particular, we complement CSA's existing heuristics that remove spurious bug reports. We encode the path constraints produced by CSA as Satisfiability Modulo Theories (SMT) problems, use SMT solvers to precisely check them for satisfiability, and remove bug reports whose associated path constraints are unsatisfiable. Our refutation extension refutes spurious bug reports in 8 out of 12 widely used open-source applications; on average, it refutes ca. 7% of all bug reports, and never refutes any true bug report. It incurs only negligible performance overheads, and on average adds 1.2% to the runtime of the full Clang/LLVM toolchain. A demonstration is available at https://www.youtube.com/watch?v=ylW5iRYNsGA
Variations on the Author
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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