3,335 research outputs found
An efficient and secure RSA--like cryptosystem exploiting R\'edei rational functions over conics
We define an isomorphism between the group of points of a conic and the set
of integers modulo a prime equipped with a non-standard product. This product
can be efficiently evaluated through the use of R\'edei rational functions. We
then exploit the isomorphism to construct a novel RSA-like scheme. We compare
our scheme with classic RSA and with RSA-like schemes based on the cubic or
conic equation. The decryption operation of the proposed scheme turns to be two
times faster than RSA, and involves the lowest number of modular inversions
with respect to other RSA-like schemes based on curves. Our solution offers the
same security as RSA in a one-to-one communication and more security in
broadcast applications.Comment: 18 pages, 1 figur
Identities for generalized Appell functions and the blow-up formula
In this paper, we prove identities for a class of generalized Appell
functions which are based on the root lattice. The
identities are reminiscent of periodicity relations for the classical Appell
function, and are proven using only analytic properties of the functions.
Moreover they are a consequence of the blow-up formula for generating functions
of invariants of moduli spaces of semi-stable sheaves of rank 3 on rational
surfaces. Our proof confirms that in the latter context, different routes to
compute the generating function (using the blow-up formula and wall-crossing)
do arrive at identical -series. The proof also gives a clear procedure for
how to prove analogous identities for generalized Appell functions appearing in
generating functions for sheaves with rank
Response of Unruh-DeWitt detector with time-dependent acceleration
It is well known that a detector, coupled linearly to a quantum field and
accelerating through the inertial vacuum with a constant acceleration , will
behave as though it is immersed in a radiation field with temperature
. We study a generalization of this result for detectors moving
with a time-dependent acceleration along a given direction. After
defining the rate of excitation of the detector appropriately, we evaluate this
rate for time-dependent acceleration, , to linear order in the
parameter . In this case, we have three length scales in
the problem: and where is the
energy difference between the two levels of the detector at which the spectrum
is probed. We show that: (a) When ,
the rate of transition of the detector corresponds to a slowly varying
temperature , as one would have expected. (b)
However, when , we find that the
spectrum is modified \textit{even at the order }. This is
counter-intuitive because, in this case, the relevant frequency does not probe
the rate of change of the acceleration since and we
certainly do not have deviation from the thermal spectrum when .
This result shows that there is a subtle discontinuity in the behaviour of
detectors with and being arbitrarily small. We
corroborate this result by evaluating the detector response for a particular
trajectory which admits an analytic expression for the poles of the Wightman
function.Comment: v1, 7 pages, no figures; v2, an Acknowledgment and some clarifying
comments added, matches version accepted for publication in Physics Letters
MEDAPs: secure multi-entities delegated authentication protocols for mobile cloud computing
Since the technology of mobile cloud computing has brought a lot of benefits to information world, many applications in mobile devices based on cloud have emerged and boomed in the last years. According to the storage limitation, data owners would like to upload and further share the data through the cloud. Due to the safety requirements, mobile data owners are requested to provide credentials such as authentication tags along with the data. However, it is impossible to require mobile data owners to provide every authenticated computational results. The solution that signersâ privilege is outsourced to the cloud would be a promising way. To solve this problem, we propose three secure multi-entities delegated authentication protocols (MEDAPs) in mobile cloud computing, which enables the multiple mobile data owners to authorize a group designated cloud servers with the signing rights. The security of MEDAPs is constructed on three cryptographic primitive identity-based multi-proxy signature (IBMPS), identity-based proxy multi-signature (IBPMS), and identity-based multi-proxy multi-signature (IBMPMS), relied on the cubic residues, equaling to the integer factorization assumption. We also give the formal security proof under adaptively chosen message attacks and chosen identity/warrant attacks. Furthermore,compared with the pairing based protocol, MEDAPs are quite efficient and the communication overhead is nearly not a linear growth with the number of cloud servers. Copyrightâc 2015 John Wiley & Sons, Ltd
The non-birefringent limit of all linear, skewonless media and its unique light-cone structure
Based on a recent work by Schuller et al., a geometric representation of all
skewonless, non-birefringent, linear media is obtained. The derived
constitutive law is based on a "core", encoding the optical metric up to a
constant. All further corrections are provided by two (anti-)selfdual
bivectors, and an "axion". The bivectors are found to vanish if the optical
metric has signature (3,1) - that is, if the Fresnel equation is hyperbolic. We
propose applications of this result in the context of transformation optics and
premetric electrodynamics.Comment: 12 pages, REVTeX; v2: typos; v3: relevant changes in text,
reorganization of manuscript; v4: new section added, final version, to appear
in Annalen der Physi
Protein structure recognition: from eigenvector analysis to structural threading method
In this work, we try to understand the protein folding problem using pair-wise hydrophobic interaction as the dominant interaction for the protein folding process. We found a strong correlation between amino acid sequence and the corresponding native structure of the protein. Some applications of this correlation were discussed in this dissertation include the domain partition and a new structural threading method as well as the performance of this method in the CASP5 competition.;In the first part, we give a brief introduction to the protein folding problem. Some essential knowledge and progress from other research groups was discussed. This part include discussions of interactions among amino acids residues, lattice HP model, and the designablity principle.;In the second part, we try to establish the correlation between amino acid sequence and the corresponding native structure of the protein. This correlation was observed in our eigenvector study of protein contact matrix. We believe the correlation is universal, thus it can be used in automatic partition of protein structures into folding domains.;In the third part, we discuss a threading method based on the correlation between amino acid sequence and ominant eigenvector of the structure contact-matrix. A mathematically straightforward iteration scheme provides a self-consistent optimum global sequence-structure alignment. The computational efficiency of this method makes it possible to search whole protein structure databases for structural homology without relying on sequence similarity. The sensitivity and specificity of this method is discussed, along with a case of blind test prediction.;In the appendix, we list the overall performance of this threading method in CASP5 blind test in comparison with other existing approaches
Spinning AdS Loop Diagrams: Two Point Functions
We develop a systematic approach to evaluating AdS loop amplitudes based on
the spectral (or "split") representation of bulk-to-bulk propagators, which
re-expresses loop diagrams in terms of spectral integrals and higher-point tree
diagrams. In this work we focus on 2pt one-loop Witten diagrams involving
totally symmetric fields of arbitrary mass and integer spin. As an application
of this framework, we study the contribution to the anomalous dimension of
higher-spin currents generated by bubble diagrams in higher-spin gauge theories
on AdS.Comment: 54+23 pages, 15 figures. v2: Section 2.2 added with more details on
the analytic evaluation of anomalous dimensions from bubble diagrams.
References added, matches published versio
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