4,489 research outputs found
Breaking a Chaotic Cryptographic Scheme Based on Composition Maps
Recently, a chaotic cryptographic scheme based on composition maps was
proposed. This paper studies the security of the scheme and reports the
following findings: 1) the scheme can be broken by a differential attack with
chosen-plaintext, where is the size of
plaintext and is the number of different elements in plain-text; 2) the
scheme is not sensitive to the changes of plaintext; 3) the two composition
maps do not work well as a secure and efficient random number source.Comment: 9 pages, 7 figure
Structure and evolution of strange attractors in non-elastic triangular billiards
We study pinball billiard dynamics in an equilateral triangular table. In
such dynamics, collisions with the walls are non-elastic: the outgoing angle
with the normal vector to the boundary is a uniform factor
smaller than the incoming angle. This leads to contraction in phase space for
the discrete-time dynamics between consecutive collisions, and hence to
attractors of zero Lebesgue measure, which are almost always fractal strange
attractors with chaotic dynamics, due to the presence of an expansion
mechanism. We study the structure of these strange attractors and their
evolution as the contraction parameter is varied. For in
the interval (0, 1/3), we prove rigorously that the attractor has the structure
of a Cantor set times an interval, whereas for larger values of the
billiard dynamics gives rise to nonaccessible regions in phase space. For
close to 1, the attractor splits into three transitive components,
the basins of attraction of which have fractal basin boundaries.Comment: 12 pages, 10 figures; submitted for publication. One video file
available at http://sistemas.fciencias.unam.mx/~dsanders
Breaking an image encryption algorithm based on chaos
Recently, a chaos-based image encryption algorithm called MCKBA (Modified
Chaotic-Key Based Algorithm) was proposed. This paper analyzes the security of
MCKBA and finds that it can be broken with a differential attack, which
requires only four chosen plain-images. Performance of the attack is verified
by experimental results. In addition, some defects of MCKBA, including
insensitivity with respect to changes of plain-image/secret key, are reported.Comment: 10 pages, 4 figure
Out-of-equilibrium mechanochemistry and self-organization of fluid membranes interacting with curved proteins
The function of biological membranes is controlled by the interaction of the fluid lipid bilayer with various proteins, some of which induce or react to curvature. These proteins can preferentially bind or diffuse towards curved regions of the membrane, induce or stabilize membrane curvature and sequester membrane area into protein-rich curved domains. The resulting tight interplay between mechanics and chemistry is thought to control organelle morphogenesis and dynamics, including traffic, membrane mechanotransduction, or membrane area regulation and tension buffering. Despite all these processes are fundamentally dynamical, previous work has largely focused on equilibrium and a self-consistent theoretical treatment of the dynamics of curvature sensing and generation has been lacking. Here, we develop a general theoretical and computational framework based on a nonlinear Onsager’s formalism of irreversible thermodynamics for the dynamics of curved proteins and membranes. We develop variants of the model, one of which accounts for membrane curving by asymmetric crowding of bulky off-membrane protein domains. As illustrated by a selection of test cases, the resulting governing equations and numerical simulations provide a foundation to understand the dynamics of curvature sensing, curvature generation, and more generally membrane curvature mechano-chemistry
On the large N limit, W_\infty Strings, Star products, AdS/CFT Duality, Nonlinear Sigma Models on AdS spaces and Chern-Simons p-branes
It is shown that the large limit of SU(N) YM in -dim
backgrounds can be subsumed by a higher dimensional gravitational theory
which can be identified to an -dim generally invariant gauge theory of diffs
, where is an -dim internal space (Cho, Sho, Park, Yoon). Based on
these findings, a very plausible geometrical interpretation of the
correspondence could be given. Conformally invariant sigma models in
dimensions with target non-compact SO(2n,1) groups are reviewed. Despite the
non-compact nature of the SO(2n,1), the classical action and Hamiltonian are
positive definite. Instanton field configurations are found to correspond
geometrically to conformal ``stereographic'' mappings of into the
Euclidean signature spaces. The relation between Self Dual branes
and Chern-Simons branes, High Dimensional Knots, follows. A detailed discussion
on symmetry is given and we outline the Vasiliev procedure to
construct an action involving higher spin massless fields in . This
spacetime higher spin theory should have a one-to-one correspondence to
noncritical strings propagating on .Comment: 43 pages, Tex fil
On the security of a new image encryption scheme based on chaotic map lattices
This paper reports a detailed cryptanalysis of a recently proposed encryption
scheme based on the logistic map. Some problems are emphasized concerning the
key space definition and the implementation of the cryptosystem using
floating-point operations. It is also shown how it is possible to reduce
considerably the key space through a ciphertext-only attack. Moreover, a timing
attack allows the estimation of part of the key due to the existent
relationship between this part of the key and the encryption/decryption time.
As a result, the main features of the cryptosystem do not satisfy the demands
of secure communications. Some hints are offered to improve the cryptosystem
under study according to those requirements.Comment: 8 pages, 8 Figure
Conservation laws and tachyon potentials in the sliver frame
Conservation laws have provided an elegant and efficient tool to evaluate the
open string field theory interaction vertex, they have been originally
implemented in the case where the string field is expanded in the Virasoro
basis. In this work we derive conservation laws in the case where the string
field is expanded in the so-called sliver -basis. As an
application of these conservation laws derived in the sliver frame, we compute
the open string field action relevant to the tachyon condensation and in order
to present not only an illustration but also an additional information, we
evaluate the action without imposing a gauge choice.Comment: 26 pages, some typos fixed, comments added, references adde
Comments on regularization of identity based solutions in string field theory
We analyze the consistency of the recently proposed regularization of an
identity based solution in open bosonic string field theory. We show that the
equation of motion is satisfied when it is contracted with the regularized
solution itself. Additionally, we propose a similar regularization of an
identity based solution in the modified cubic superstring field theory.Comment: 24 pages, two subsections added, two references adde
Improving translation initiation site and stop codon recognition by using more than two classes
Motivation: The recognition of translation initiation sites and stop codons is a fundamental part of any gene recognition program. Currently, the most successful methods use powerful classifiers, such as support vector machines with various string kernels. These methods all use two classes, one of positive instances and another one of negative instances that are constructed using sequences from the whole genome. However, the features of the negative sequences differ depending on the position of the negative samples in the gene. There are differences depending on whether they are from exons, introns, intergenic regions or any other functional part of the genome. Thus, the positive class is fairly homogeneous, as all its sequences come from the same part of the gene, but the negative class is composed of different instances. The classifier suffers from this problem. In this article, we propose the training of different classifiers with different negative, more homogeneous, classes and the combination of these classifiers for improved accuracy. Results: The proposed method achieves better accuracy than the best state-of-the-art method, both in terms of the geometric mean of the specificity and sensitivity and the area under the receiver operating characteristic and precision recall curves. The method is tested on the whole human genome. The results for recognizing both translation initiation sites and stop codons indicated improvements in the rates of both false-negative results (FN) and false-positive results (FP). On an average, for translation initiation site recognition, the false-negative ratio was reduced by 30.2% and the FP ratio decreased by 10.9%. For stop codon prediction, FP were reduced by 41.4% and FN by 31.7%. Availability and implementation: The source code is licensed under the General Public License and is thus freely available. The datasets and source code can be obtained from http://cib.uco.es/site-recognition. Contact: [email protected]
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