1,720,984 research outputs found
Privacy Protection for Authentication Protocols
No full textIn our highly computerized and networked society, privacy of individuals is precious and becomes increasingly important.
Problems particularly arise in the context of authentication protocols where, as a general rule, entities actively reveal their respective identities to each other.
To encounter this issue, different privacy-preserving authentication methods have been developed in the last decades.
The list of these techniques comprises, apart from identity escrow, ring authentication, hidden and anonymous credentials, and several others, the concept of affiliation-hiding authentication (AHA).
Such protocols offer the appealing and seemingly contradictory service to enable users to authenticate each other as members of a certain group without revealing their affiliation to group outsiders.
In AHA protocols (also known as Secret Handshakes), users become group members by registering with group authorities (GAs) and obtaining individual membership credentials.
Group members then use their credentials to privately authenticate each other, optionally also establishing a secure session key.
The pivotal privacy property that contrasts AHA with classical authentication or authenticated key establishment is that parties learn each other's affiliations to groups and compute common session keys if and only if their groups match.
Prior work has succeeded in constructing AHA protocols that offer different degrees of security, privacy, and efficiency.
However, a set of essential problems have been left open.
These include a close study of the level of trust that intrinsically has to be placed into participants of such systems (including into GAs), the extension of the single-group setting with only one GA to a setting where users are affiliated to multiple groups and, through AHA, want to discover matching ones, and certainly the question of efficient implementability.
We argue that all these topics are highly relevant for practical deployment of privacy-preserving authentication in general, and AHA in particular.
In this thesis, the author concretizes and cryptographically models these challenges, and offers provably secure solutions.
Furthermore, this thesis treats privacy-related challenges that are posed in the context of network-based social interactions.
Without doubt, online social networks, that help participants to build and reflect their social relations to other participants, have taken an essential role in people's daily life.
A key step in the constitution of new links between participants consists of the reconciliation of shared contacts or friends.
The author develops techniques to discover common contacts in social networks in a privacy-aware manner, i.e., without disclosing non-matching contacts.
Besides formalizing this task and offering appropriate solutions, the thesis analyzes an interesting connection between AHA protocols and the challenge of private discovery of common contacts.
By identifying and solving a variety of relevant open problems in the context of privacy-aware authentication, this thesis contributes to wide-scale deployment of methods that respect and regain user privacy in p2p systems, mobile ad hoc networks, and social networking applications
Plaintext Awareness in Identity-Based Key Encapsulation∗†
Full text linkThe notion of plaintext awareness (PA) has many applications in public key cryptography: it offers unique, stand-alone security guarantees for public key encryption schemes, has been used as a sufficient condition for proving indistinguishability against adaptive chosen ciphertext attacks (IND-CCA), and can be used to construct privacy-preserving protocols such as deniable authentication. Unlike many other security notions, plaintext awareness is very fragile when it comes to differences between the random oracle and standard models; for example, many implications involving PA in the random oracle model are not valid in the standard model and vice versa. Similarly, strategies for proving PA of schemes in one model cannot be adapted to the other model. Existing research addresses PA in detail only in the public key setting. This paper gives the first formal exploration of plaintext awareness in the identity-based setting and, as initial work, proceeds in the random oracle model. The focus is laid mainly on identity-based key encapsulation mechanisms (IB-KEMs), for which the paper presents the first definitions of plaintext awareness, highlights the role of PA in proof strategies o
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
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
Shorter Double-Authentication Preventing Signatures for Small Address Spaces
Full text linkA recent paper by Derler, Ramacher, and Slamanig (IEEE EuroS&P 2018) constructs double-authentication preventing signatures ( DAP signatures , a specific self-enforcement enabled variant of signatures where messages consist of an address and a payload) that have---if the supported address space is not too large---keys and signatures that are considerably more compact than those of prior work. We embark on their approach to restrict attention to small address spaces and construct novel DAP schemes that beat their signature size by a factor of five and reduce the signing key size from linear to constant (the verification key size remains almost the same). We construct our DAP signatures generically from identification protocols, using a transform similar to but crucially different from that of Fiat and Shamir. We use random oracles. We don\u27t use pairings
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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