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Nearly optimal exploration-exploitation decision thresholds
Get PDFexploration-exploitation decision thresholds Christos Dimitrakakis
PvsE.eps
No full textReid et al.'s distance bounding protocol and mafia fraud attacks over noisy channels Mitrokotsa, A.; Dimitrakakis, C.; Peris-Lopez, P.; Hernandez-Castro, J.C. General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Index Terms-Contactless smart cards, RFID, distance bounding protocols, relay attacks, mafia fraud attacks. I. INTRODUCTION A NUMBER of secure and efficient authentication protocols for RF transponders such as contactless smart cards and RFID tags have been proposed recently. Most assume proximity between readers and transponders due to limited radio channel range. However, an intruder located between the tag (prover) and the reader (verifier), can trick the latter into thinking that is in close proximity. This attack can be divided into three subcategories: a) Distance fraud: The attacker is a fraudulent tag . The attack involves convincing the legitimate reader of being nearer to the legitimate tag than it really is. b) Mafia fraud c) Terrorist Fraud: The attacker = { , } is a pair of two colluding parties: a legitimate tag and a terrorist tag . The attack enables to convince the legimate reader of an assertion related to the private key of . In this attack, Manuscript received September 30, 2009. The associate editor coordinating the review of this letter and approving it for publication was C. Mitchell. A although the legitimate tag is dishonest and cooperates with the terrorist tag , the secret key shared between the legitimate tag and reader is not revealed to the terrorist tag . Distance bounding protocols were introduced in [4] to hinder distance fraud and mafia fraud attacks, by measuring the round trip delays during a rapid challenge-response exchange of bits to infer an upper bound on the distance between the verifier and the prover. Subsequently [5] proposed a distance bounding protocol offering protection against mafia fraud only. Later, Reid et al. proposed a new protocol [1] with the objectives of (a) being resistant to both mafia and terrorist fraud, and (b) suitable for low-cost RFID tags. This work can be considered a reference point in the design of distance bounding protocols for constrained RF tags. Indeed, key ideas of Contribution: We analyse the security of Reid et al.'s protocol (henceforth RP) against mafia fraud attack under noisy conditions. Due to power constraints and the wireless medium, RFID systems are particularly susceptible to noise, but its effect on the attacker has not been studied previously. In addition, we clarify RP's security under noise-free conditions. More specifically, Notation: We consider sequences = 1 , . . . , with all in some alphabet and ∈ . We write * ≜ ∪ ∞ =0 for the set of all sequences. The concatenation of with some ∈ is written as | ∈ , where ⊕ is an appropriate operator (XOR for = {0, 1}). ℙ( ) denotes the probability of event , while ≜ implies a definition. II. REID et al.'S PROTOCOL In RP [1], the reader and tag , whose identifiers are ID , ID ∈ * respectively, share a common secret ∈ . The messages exchanged are: 1) → : The reader chooses a random number ∈ and transmits it and its identity ID to the tag. 2) → : The tag chooses a random number ∈ and transmits it and its identity ID to the reader
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
Dispelling 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
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