10,917 research outputs found
Constant-size Group Signatures from Lattices
Lattice-based group signature is an active research topic in
recent years. Since the pioneering work by Gordon, Katz and Vaikuntanathan
(Asiacrypt 2010), ten other schemes have been proposed,
providing various improvements in terms of security, efficiency and functionality.
However, in all known constructions, one has to fix the number of group users in the setup stage, and as a consequence, the signature sizes are dependent on .
In this work, we introduce the first constant-size group signature from lattices, which means that the size of signatures produced by the scheme is independent of and only depends on the security parameter . More precisely, in our scheme, the sizes of signatures, public key and users\u27 secret keys are all of order . The scheme supports dynamic enrollment of users and is proven secure in the random oracle model under the Ring Short Integer Solution (RSIS) and Ring Learning With Errors (RLWE) assumptions. At the heart of our design is a zero-knowledge argument of knowledge of a valid message-signature pair for the Ducas-Micciancio signature scheme (Crypto 2014), that may be of independent interest
Information entropy in fragmenting systems
The possibility of facing critical phenomena in nuclear fragmentation is a
topic of great interest. Different observables have been proposed to identify
such a behavior, in particular, some related to the use of information entropy
as a possible signal of critical behavior. In this work we critically examine
some of the most widespread used ones comparing its performance in bond
percolation and in the analysis of fragmenting Lennard Jones Drops.Comment: 3 pages, 3 figure
Dimensional Crossover in Bragg Scattering from an Optical Lattice
We study Bragg scattering at 1D optical lattices. Cold atoms are confined by
the optical dipole force at the antinodes of a standing wave generated inside a
laser-driven high-finesse cavity. The atoms arrange themselves into a chain of
pancake-shaped layers located at the antinodes of the standing wave. Laser
light incident on this chain is partially Bragg-reflected. We observe an
angular dependence of this Bragg reflection which is different to what is known
from crystalline solids. In solids the scattering layers can be taken to be
infinitely spread (3D limit). This is not generally true for an optical lattice
consistent of a 1D linear chain of point-like scattering sites. By an explicit
structure factor calculation we derive a generalized Bragg condition, which is
valid in the intermediate regime. This enables us to determine the aspect ratio
of the atomic lattice from the angular dependance of the Bragg scattered light.Comment: 4 pages, 5 figure
Limit shape and height fluctuations of random perfect matchings on square-hexagon lattices
We study asymptotics of perfect matchings on a large class of graphs called
the contracting square-hexagon lattice, which is constructed row by row from
either a row of a square grid or a row of a hexagonal lattice. We assign the
graph periodic edge weights with period , and consider the
probability measure of perfect matchings in which the probability of each
configuration is proportional to the product of edge weights. We show that the
partition function of perfect matchings on such a graph can be computed
explicitly by a Schur function depending on the edge weights. By analyzing the
asymptotics of the Schur function, we then prove the Law of Large Numbers
(limit shape) and the Central Limit Theorem (convergence to the Gaussian free
field) for the corresponding height functions. We also show that the
distribution of certain type of dimers near the turning corner is the same as
the eigenvalues of Gaussian Unitary Ensemble, and that in the scaling limit
under the boundary condition that each segment of the bottom boundary grows
linearly with respect the dimension of the graph, the frozen boundary is a
cloud curve whose number of tangent points to the bottom boundary of the domain
depends on the size of the period, as well as the number of segments along the
bottom boundary
Lattice-Based Group Signatures: Achieving Full Dynamicity (and Deniability) with Ease
In this work, we provide the first lattice-based group signature that offers
full dynamicity (i.e., users have the flexibility in joining and leaving the
group), and thus, resolve a prominent open problem posed by previous works.
Moreover, we achieve this non-trivial feat in a relatively simple manner.
Starting with Libert et al.'s fully static construction (Eurocrypt 2016) -
which is arguably the most efficient lattice-based group signature to date, we
introduce simple-but-insightful tweaks that allow to upgrade it directly into
the fully dynamic setting. More startlingly, our scheme even produces slightly
shorter signatures than the former, thanks to an adaptation of a technique
proposed by Ling et al. (PKC 2013), allowing to prove inequalities in
zero-knowledge. Our design approach consists of upgrading Libert et al.'s
static construction (EUROCRYPT 2016) - which is arguably the most efficient
lattice-based group signature to date - into the fully dynamic setting.
Somewhat surprisingly, our scheme produces slightly shorter signatures than the
former, thanks to a new technique for proving inequality in zero-knowledge
without relying on any inequality check. The scheme satisfies the strong
security requirements of Bootle et al.'s model (ACNS 2016), under the Short
Integer Solution (SIS) and the Learning With Errors (LWE) assumptions.
Furthermore, we demonstrate how to equip the obtained group signature scheme
with the deniability functionality in a simple way. This attractive
functionality, put forward by Ishida et al. (CANS 2016), enables the tracing
authority to provide an evidence that a given user is not the owner of a
signature in question. In the process, we design a zero-knowledge protocol for
proving that a given LWE ciphertext does not decrypt to a particular message
Chiral spin density wave, spin-charge-Chern liquid and d+id superconductivity in 1/4-doped correlated electronic systems on the honeycomb lattice
Recently two interesting candidate quantum phases --- the chiral spin density
wave state featuring anomalous quantum Hall effect and the d+id superconductor
--- were proposed for the Hubbard model on the honeycomb lattice at 1/4 doping.
Using a combination of exact diagonalization, density matrix renormalization
group, the variational Monte Carlo method and quantum field theories, we study
the quantum phase diagrams of both the Hubbard model and t-J model on the
honeycomb lattice at 1/4-doping. The main advantage of our approach is the use
of symmetry quantum numbers of ground state wavefunctions on finite size
systems (up to 32 sites) to sharply distinguish different quantum phases. Our
results show that for in the Hubbard model and for in the t-J model, the quantum ground state is either a chiral spin
density wave state or a spin-charge-Chern liquid, but not a d+id
superconductor. However, in the t-J model, upon increasing the system goes
through a first-order phase transition at into the d+id
superconductor. Here the spin-charge-Chern liquid state is a new type of
topologically ordered quantum phase with Abelian anyons and fractionalized
excitations. Experimental signatures of these quantum phases, such as tunneling
conductance, are calculated. These results are discussed in the context of
1/4-doped graphene systems and other correlated electronic materials on the
honeycomb lattice.Comment: Some parts of text revised for clarity of presentatio
The Nambu-Jona-Lasinio model with staggered fermions
We investigate the neighbourhood of the chiral phase transition in a lattice
Nambu--Jona-Lasinio model, using both Monte Carlo methods and lattice
Schwinger-Dyson equations.Comment: Talks at LAT93, Dallas, U.S.A. Postscript file, 6 pages, figures
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