111,989 research outputs found
Quantum Multi-Prover Interactive Proof Systems with Limited Prior Entanglement
This paper gives the first formal treatment of a quantum analogue of
multi-prover interactive proof systems. It is proved that the class of
languages having quantum multi-prover interactive proof systems is necessarily
contained in NEXP, under the assumption that provers are allowed to share at
most polynomially many prior-entangled qubits. This implies that, in
particular, if provers do not share any prior entanglement with each other, the
class of languages having quantum multi-prover interactive proof systems is
equal to NEXP. Related to these, it is shown that, in the case a prover does
not have his private qubits, the class of languages having quantum
single-prover interactive proof systems is also equal to NEXP.Comment: LaTeX2e, 19 pages, 2 figures, title changed, some of the sections are
fully revised, journal version in Journal of Computer and System Science
Foundations, Properties, and Security Applications of Puzzles: A Survey
Cryptographic algorithms have been used not only to create robust ciphertexts
but also to generate cryptograms that, contrary to the classic goal of
cryptography, are meant to be broken. These cryptograms, generally called
puzzles, require the use of a certain amount of resources to be solved, hence
introducing a cost that is often regarded as a time delay---though it could
involve other metrics as well, such as bandwidth. These powerful features have
made puzzles the core of many security protocols, acquiring increasing
importance in the IT security landscape. The concept of a puzzle has
subsequently been extended to other types of schemes that do not use
cryptographic functions, such as CAPTCHAs, which are used to discriminate
humans from machines. Overall, puzzles have experienced a renewed interest with
the advent of Bitcoin, which uses a CPU-intensive puzzle as proof of work. In
this paper, we provide a comprehensive study of the most important puzzle
construction schemes available in the literature, categorizing them according
to several attributes, such as resource type, verification type, and
applications. We have redefined the term puzzle by collecting and integrating
the scattered notions used in different works, to cover all the existing
applications. Moreover, we provide an overview of the possible applications,
identifying key requirements and different design approaches. Finally, we
highlight the features and limitations of each approach, providing a useful
guide for the future development of new puzzle schemes.Comment: This article has been accepted for publication in ACM Computing
Survey
Supporting active database learning and training through interactive multimedia
The learning objectives of a database course include aspects from conceptual and theoretical knowledge to practical development and implementation skills. We present an interactive educational multimedia system based on the virtual apprenticeship model for the knowledge- and skills-oriented Web-based education of database course students. Combining knowledge learning and skills training in an integrated environment is a central aspect of our system. We show that tool-mediated independent learning and training in an authentic setting is an alternative to traditional classroom-based approaches
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