108,584 research outputs found
Effective Privacy Amplification for Secure Classical Communications
We study the practical effectiveness of privacy amplification for classical
key-distribution schemes. We find that in contrast to quantum key distribution
schemes, the high fidelity of the raw key generated in classical systems allow
the users to always sift a secure shorter key if they have an upper bound on
the eavesdropper probability to correctly guess the exchanged key-bits. The
number of privacy amplification iterations needed to achieve information leak
of 10^-8 in existing classical communicators is 2 or 3 resulting in a
corresponding slowdown 4 to 8. We analyze the inherent tradeoff between the
number of iterations and the security of the raw key. This property which is
unique to classical key distribution systems render them highly useful for
practical, especially for noisy channels where sufficiently low quantum bit
error ratios are difficult to achieve.Comment: 11 pages, 3 figure
Usability of Humanly Computable Passwords
Reusing passwords across multiple websites is a common practice that
compromises security. Recently, Blum and Vempala have proposed password
strategies to help people calculate, in their heads, passwords for different
sites without dependence on third-party tools or external devices. Thus far,
the security and efficiency of these "mental algorithms" has been analyzed only
theoretically. But are such methods usable? We present the first usability
study of humanly computable password strategies, involving a learning phase (to
learn a password strategy), then a rehearsal phase (to login to a few
websites), and multiple follow-up tests. In our user study, with training,
participants were able to calculate a deterministic eight-character password
for an arbitrary new website in under 20 seconds
Why the Tsirelson bound?
Wheeler's question 'why the quantum' has two aspects: why is the world
quantum and not classical, and why is it quantum rather than superquantum,
i.e., why the Tsirelson bound for quantum correlations? I discuss a remarkable
answer to this question proposed by Pawlowski et al (2009), who provide an
information-theoretic derivation of the Tsirelson bound from a principle they
call 'information causality.'Comment: 17 page
Finding All Solutions of Equations in Free Groups and Monoids with Involution
The aim of this paper is to present a PSPACE algorithm which yields a finite
graph of exponential size and which describes the set of all solutions of
equations in free groups as well as the set of all solutions of equations in
free monoids with involution in the presence of rational constraints. This
became possible due to the recently invented emph{recompression} technique of
the second author.
He successfully applied the recompression technique for pure word equations
without involution or rational constraints. In particular, his method could not
be used as a black box for free groups (even without rational constraints).
Actually, the presence of an involution (inverse elements) and rational
constraints complicates the situation and some additional analysis is
necessary. Still, the recompression technique is general enough to accommodate
both extensions. In the end, it simplifies proofs that solving word equations
is in PSPACE (Plandowski 1999) and the corresponding result for equations in
free groups with rational constraints (Diekert, Hagenah and Gutierrez 2001). As
a byproduct we obtain a direct proof that it is decidable in PSPACE whether or
not the solution set is finite.Comment: A preliminary version of this paper was presented as an invited talk
at CSR 2014 in Moscow, June 7 - 11, 201
Information Causality, the Tsirelson Bound, and the 'Being-Thus' of Things
The principle of `information causality' can be used to derive an upper
bound---known as the `Tsirelson bound'---on the strength of quantum mechanical
correlations, and has been conjectured to be a foundational principle of
nature. To date, however, it has not been sufficiently motivated to play such a
foundational role. The motivations that have so far been given are, as I argue,
either unsatisfactorily vague or appeal to little if anything more than
intuition. Thus in this paper I consider whether some way might be found to
successfully motivate the principle. And I propose that a compelling way of so
doing is to understand it as a generalisation of Einstein's principle of the
mutually independent existence---the `being-thus'---of spatially distant
things. In particular I first describe an argument, due to Demopoulos, to the
effect that the so-called `no-signalling' condition can be viewed as a
generalisation of Einstein's principle that is appropriate for an irreducibly
statistical theory such as quantum mechanics. I then argue that a compelling
way to motivate information causality is to in turn consider it as a further
generalisation of the Einsteinian principle that is appropriate for a theory of
communication. I describe, however, some important conceptual obstacles that
must yet be overcome if the project of establishing information causality as a
foundational principle of nature is to succeed.Comment: '*' footnote added to page 1; 24 pages, 1 figure; Forthcoming in
Studies in History and Philosophy of Modern Physic
A PSYCHOLINGUISTIC ANALYSIS OF DYSLEXIA IN BACKWARDS: THE RIDDLE OF DYSLEXIA
This study is under a psycholinguistic umbrella. The aim of this study is to
analyze linguistic phenomena of dyslexia suffered by Brian, the main character in
Backwards: The Riddle of Dyslexia. This study has three objectives: (1) to
identify and explain the types of linguistic errors experienced by the main
character in Backwards: The Riddle of Dyslexia; (2) to examine the environmental
factors which occur in the movie; and (3) to describe the kinds of teaching
approaches used to recover the main character in the movie from dyslexia.
This study employed a descriptive qualitative method since it emphasized on
describing the phenomena of dyslexia in Backwards: The Riddle of Dyslexia.
Moreover, the findings were presented in narrative or textual description.
However, number was also used to support the analysis of the data. Some steps in
analyzing the data were: identifying the raw data, classifying each datum into the
categorization, analyzing each datum, interpreting each datum based on its
contexts, reporting the findings, and drawing the conclusion. Finally, the data
findings were triangulated by two linguistics students who were keen on
psycholinguistics.
This study reveals three findings. First, of eight types of miscues, only six
types occur in Backwards: The Riddle of Dyslexia. They are substitution,
hesitation, omission, non-response, addition, and self-corrections. Meanwhile, the
absent types are repetition and reversal. Substitution is the most common error
made by a dyslexic who has problems in extracting printed letters into sounds.
Meanwhile, the other types have only small occurrences since they are not
common errors made by a dyslexic. Second, all types of environmental factors
occur in the movie, i.e. social interaction and communication, physical
environment, cognitive modality preference, emotional motivation, and children’s
behavior. Social interaction and communication as well as physical environment
become the highest in rank because Brian works well with another and needs a
suitable condition and situation to read. Finally, each type of environmental
factors supports successful teaching approaches for a dyslexic. Third, types of
teaching approaches which occur in the movie are language experience, teacher
modeling, self-questioning, phonological approach, and engaging parents.
Meanwhile, the absent types are creative writing and critical literacy. Those
present types of teaching approaches have represented successful treatments for
Brian to recover from dyslexia.
Key words: psycholinguistics, dyslexia, Backwards: The Riddle of Dyslexi
Noise and disturbance in quantum measurements: an information-theoretic approach
We introduce information-theoretic definitions for noise and disturbance in
quantum measurements and prove a state-independent noise-disturbance tradeoff
relation that these quantities have to satisfy in any conceivable setup.
Contrary to previous approaches, the information-theoretic quantities we define
are invariant under relabelling of outcomes, and allow for the possibility of
using quantum or classical operations to `correct' for the disturbance. We also
show how our bound implies strong tradeoff relations for mean square
deviations.Comment: v3: to appear on PRL (some issues fixed, supplemental material
expanded). v2: replaced with submitted version; 5 two-column pages + 6
one-column pages + 3 figures; one issue corrected and few references added.
v1: 17 pages, 3 figure
Novice Ideas: Handwriting Comparisons Conducted by an Untrained Individual
Forensic analysis of questioned documents includes chemical analyses of paper and ink as well as handwriting comparisons. Several elements affect handwriting analyses, including the presence of discriminatory factors that can individualize a handwriting sample and whether the handwriting has been disguised. Five handwriting samples were gathered from six individuals comprising of one reference, three natural unknowns, and one disguised sample per person. A novice conducted analyses on every collected sample and conducted comparisons of the reference sample to the unknown and disguised samples in an attempt to correctly source the unknown and disguised samples. The novice showed a high level of accuracy in correctly sourcing the natural sample but made erroneous conclusions when analyzing the disguised samples
- …