1,721,009 research outputs found
Fourth Conference on Security in Communication Networks (SCN '04)
No full textPrefazione (capitolo di libro
A Software Infrastructure for Authenticated Web Metering
No full textAs the popularity of the Internet and the number of resources available on it have grown, potential customers are increasingly turning to it for information about products and services. Accordingly, online advertising is gaining a significant portion of the advertising market.
The Internet has become a mainstream advertising channel, surpassing traditional media such as newspapers and radio in number of advertisements. Many businesses, such as retail stores, travel agencies, airlines, and employment services, now depend on the Internet. According to an Interactive Advertising Bureau (IAB) report, Internet advertisers in the US spent almost $3 billion in the first six months of 2002, despite lower investments due to the economic and political environments.(1)
The same mechanisms ruling traditional advertising venues rule online advertising. Advertisers exploit the popularity of the best-known Web sites, typically search engines or portals, to advertise their products and reach the most potential customers. What is different is how advertisers measure ad exposure.
Traditional rating systems are of little value when applied to the Internet because of the enormous number of Web pages available to online advertisements. Counting accesses to a Web service is a difficult task and the data may be unreliable. Although the host servers usually collect the usage data, organizations might be tempted to inflate the number of registered accesses. Even a trusted host site can generate statistics that do not correspond to real usage.
Several metering techniques attempt to accurately measure the number of visits a site receives and hence the advertising exposure,(2,3) but advertisers and auditing companies haven't adopted a standard technique. Auditing companies base their measures of a Web site's popularity on statistics or market surveys.
We propose a framework based on hash chains.(4,5) Unlike similar approaches, our implementation minimizes the overhead associated with the additional communication required to implement the protocol while providing an efficient and flexible scheme. Furthermore, the resulting framework offers additional guarantees such as security and nonrepudiation of the produced proof of visits
Probabilistic Visual Cryptography Schemes
No full textVisual cryptography schemes allow the encoding of a secret image,
consisting of black or white pixels, into n shares which are
distributed to the participants. The shares are such that only
qualified subsets of participants can ``visually'' recover the
secret image. The secret pixels are shared with techniques that
subdivide each secret pixel into a certain number m, m>= 2 of
subpixels. Such a parameter is called the pixel expansion.
Recently Yang introduced a probabilistic model. In such a model the
pixel expansion m is 1, that is, there is no pixel expansion.
The reconstruction of the image however is probabilistic, meaning
that a secret pixel will be correctly reconstructed only with a
certain probability.
In this paper we propose a generalization of the model proposed by
Yang. In our model we fix the pixel expansion m >= 1 that we can
tolerate and we consider probabilistic schemes attaining such a
pixel expansion. For m=1 our model reduces to the one of Yang. For
big enough values of m, for which a deterministic scheme exists,
our model reduces to the classical deterministic model. We show that
between these two extremes one can trade the probability factor of
the scheme with the pixel expansion. Moreover we prove that there
is a one-to-one mapping between deterministic schemes and probabilistic
schemes with no pixel expansion, where the contrast is traded for
the probability factor
Managing Constraints in Role Based Access Control
Full text linkRole-based access control (RBAC) is the most popular access control model currently adopted in several contexts to define security management. Constraints play a crucial role since they can drive the selection of the best representation of the organization's security policies when migrating towards an RBAC system. In this paper, we examine different types of constraints addressing both theoretical aspects and practical considerations. On one side, we define the constrained role mining problem for each constraint type, showing its complexity. On the other hand, we present efficient heuristics adapted to each class of constraints, all derived from the specialization of a general approach for role mining. We show that our techniques improve over previous proposals, offering a complete set of experimentations obtained after the application of the heuristics to standard real-world datasets
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