arXiv subjects

Gang Hu

Publications and source records attributed to Gang Hu.

53 records · Page 3Linked to original sources

arXiv2005

Chaotic Turing Patterns displaying the beauty of chaos

The problem of Turing pattern formation has attracted much attention in nonlinear science as well as physics, chemistry and biology. So far all Turing patterns have been observed in stationary and oscillatory media only. In this letter we find for the first time that ordered Turing patterns exist in chaotic extended systems. And chaotic Turing patterns are strikingly rich and surprisingly beautiful with their space structures. These findings are in sharp contrast with the intuition of pseudo-randomness of chaos. The richness and beauty of the chaotic Turing patterns are attributed to a large variety of symmetry properties realized by various types of self-organizations of partial chaos synchronizations. Some statistical measurements are performed to confirm and heuristically understand these findings.

nlin.PS↗

arXiv2005

A new self-synchronizing stream cipher

A new self-synchronizing stream cipher (SSSC) is proposed based on one-way and nearest neighbor coupled integer maps. Some ideas of spatiotemporal chaos synchronization and chaotic cryptography are applied in this new SSSC system. Several principles of constructing optimal SSSC are discussed, and the methods realizing these principles are specified. This SSSC is compared with several SSSC systems in security by applying chosen-ciphertext attacks. It is shown that our new system can provide SSSC with high security and fairly fast performance.

nlin.CD↗

arXiv2004

Experimental realization of a highly secure chaos communication under strong channel noise

A one-way coupled spatiotemporally chaotic map lattice is used to contruct cryptosystem. With the combinatorial applications of both chaotic computations and conventional algebraic operations, our system has optimal cryptographic properties much better than the separative applications of known chaotic and conventional methods. We have realized experiments to pratice duplex voice secure communications in realistic Wired Public Switched Telephone Network by applying our chaotic system and the system of Advanced Encryption Standard (AES), respectively, for cryptography. Our system can work stably against strong channel noise when AES fails to work.

nlin.CD↗

arXiv2004

Periodicity of chaotic trajectories in realizations of finite computer precisions and its implication in chaos communications

Fundamental problems of periodicity and transient process to periodicity of chaotic trajectories in computer realization with finite computation precision is investigated by taking single and coupled Logistic maps as examples. Empirical power law relations of the period and transient iterations with the computation precisions and the sizes of coupled systems are obtained. For each computation we always find, by randomly choosing initial conditions, a single dominant periodic trajectory which is realized with major portion of probability. These understandings are useful for possible applications of chaos, e.g., chaotic cryptography in secure communication.

nlin.CD↗

arXiv2003

Turbulence control by developing a spiral wave with a periodic signal injection in the complex Ginzburg-Landau equation

Turbulence control in the two-dimensional complex Ginzburg-Landau equation is investigated. A new approach is proposed for the control purpose. In the presence of a small spiral wave seed initiation, a fully developed turbulence can be completely annihilated by injecting a single periodic signal to a small fixed space area around the spiral wave tip. The control is achieved in a parameter region where the spiral wave of the uncontrolled system is absolutely unstable. The robustness, convenience and high control efficiency of this method is emphasized, and the mechanism underlying these practical advantages are intuitively understood.

cond-mat.soft↗

arXiv2003

Chaos-based cryptograph incorporated with S-box algebraic operation

Error function analysis is an effective attack against chaotic cryptograph [PRE 66, 065202(R) (2002)]. The basin structure of the error function is crucial for determining the security of chaotic cryptosystems. In the present paper the basin behavior of the system used in [21] is analyzed in relation with the estimation of its practical security. A S-box algebraic operation is included in the chaotic cryptosystem, which considerably shrinks the basin of the error function and thus greatly enhances the practical security of the system with a little computational expense. PACS numbers: 05.45.Vx, 05.45.Ra

nlin.CD↗

arXiv2003

Error Function Attack of chaos synchronization based encryption schemes

Different chaos synchronization based encryption schemes are reviewed and compared from the practical point of view. As an efficient cryptanalysis tool for chaos encryption, a proposal based on the Error Function Attack is presented systematically and used to evaluate system security. We define a quantitative measure (Quality Factor) of the effective applicability of a chaos encryption scheme, which takes into account the security, the encryption speed, and the robustness against channel noise. A comparison is made of several encryption schemes and it is found that a scheme based on one-way coupled chaotic map lattices performs outstandingly well, as judged from Quality Factor.

nlin.PS↗

arXiv2003

A spatiotemporal-chaos-based cryptosystem taking advantages of both synchronous and self-synchronizing schemes

Two-dimensional one-way coupled map lattices are used for cryptograph where multiple space units produce chaotic outputs in parallel. One of the outputs plays the role of driving for synchronization of the decryption system while the others perform the function of information encoding. With this separation of functions the receiver can establish a self-checking and self-correction mechanism, and enjoys the advantages of both synchronous and self-synchronizing schemes. A comparison between the present system with the system of Advanced Encryption Standard, AES, is presented in the aspect of channel noise influence. Numerical investigations show that our system is much stronger than AES against channel noise perturbations, and thus can be better used for secure communications with large noise channel exists in open channels, e.g., mobile-phone secure communications.

nlin.CD↗

arXiv2003

A Spatiotemporal-chaos-based Encryption Having Overall Properties Considerably Better Than Advanced Encryption Standard

Spatiotemporal chaos of a two-dimensional one-way coupled map lattice is used for chaotic cryptography. The chaotic outputs of many space units are used for encryption simultaneously. This system shows satisfactory cryptographic properties of high security; fast encryption (decryption) speed; and robustness against noise disturbances in communication channel. The overall features of this spatiotemporal-chaos-based cryptosystem are better than chaotic cryptosystems known so far, and also than currently used conventional cryptosystems, such as the Advanced Encryption Standard (AES).

nlin.CD↗

arXiv2002

Transitions to Measure Synchronization in Coupled Hamiltonian Systems

Transitions to measure synchronization in two coupled $ϕ^{4}$ lattices are investigated based on numerical simulations. The relationship between measure synchronization (MS), phase locking and system's total energy is studied both for periodic and chaotic states. Two different scalings are discovered during the process to MS according to phase locking. Random walk like phase synchronization in chaotic measure synchronization is found, and phase locking interrupted by phase slips irregularly is also investigated. Meanwhile, related analysis is qualitative given to explain this phenomenon.

nlin.CD↗

arXiv2002

Transitions to equilibrium state in classical ϕ^{4} lattice

Statistical behavior of a classical $ϕ^{4}$ Hamiltonian lattice is investigated from microscopic dynamics. The largest Lyapunov exponent and entropies are considered for manifesting chaos and equipartition behaviors of the system. It is found, for the first time, that for any large while finite system size there exist two critical couplings for the transitions to equipartitions, and the scaling behaviors of these lower and upper critical couplings vs the system size is numerically obtained.

nlin.CD↗

arXiv1998

Phase slips and phase synchronization of coupled oscillators

The behaviors of coupled oscillators, each of which has periodic motion with random natural frequency in the absence of coupling, are investigated. Some novel collective phenomena are revealed. At the onset of instability of the phase-locking state, simultaneous phase slips of all oscillators and quantized phase shifts in these phase slips are observed. By incresing the coupling, a bifurcation tree from high-dimensional quasiperiodicity to chaos to quasiperiodicity and periodicity is found. Different orders of phase synchronizations of chaotic oscillators and chaotic clusters play the key role for constructing this tree structure.

chao-dyn↗

arXiv1998

Array-induced collective transport in the Brownian motion of coupled nonlinear oscillator systems

Brownian motion of an array of harmonically coupled particles subject to a periodic substrate potential and driven by an external bias is investigated. In the linear response limit (small bias), the coupling between particles may enhance the diffusion process, depending on the competition between the harmonic chain and the substrate potential. An analytical formula of the diffusion rate for the single-particle case is also obtained. In the nonlinear response regime, the moving kink may become phase-locked to its radiated phonon waves, hence the mobility of the chain may decrease as one increases the external force.

cond-mat.stat-mech↗

arXiv1998

Resonant steps and spatiotemporal dynamics in the damped dc-driven Frenkel-Kontorova chain

Kink dynamics of the damped Frenkel-Kontorova (discrete sine-Gordon) chain driven by a constant external force are investigated. Resonant steplike transitions of the average velocity occur due to the competitions between the moving kinks and their radiated phasonlike modes. A mean-field consideration is introduced to give a precise prediction of the resonant steps. Slip-stick motion and spatiotemporal dynamics on those resonant steps are discussed. Our results can be applied to studies of the fluxon dynamics of 1D Josephson-junction arrays and ladders, dislocations, tribology and other fields.

cond-mat.stat-mech↗

arXiv1997

Spatiotemporal dynamics of discrete sine-Gordon lattices with sinusoidal couplings

The spatiotemporal dynamics of a damped sine-Gordon chain with sinusoidal nearest-neighbor couplings driven by a constant uniform force are discussed. The velocity characteristics of the chain versus the external force is shown. Dynamics in the high- and low-velocity regimes are investigated. It is found that in the high-velocity regime, the dynamics is dominated by rotating modes, the velocity shows a branching bifurcation feature, while in the low-velocity regime, the velocity exhibits step-like dynamical transitions, broken by the destruction of strong resonances.

cond-mat.stat-mech↗

arXiv1996

Clustering dynamics in globally coupled map lattices

Clustering bifurcations are investigated by considering models of globally coupled map lattices. Typical classes of clustering bifurcations are revealed. The clustering bifurcation thresholds of the coupled system are closely related to the bifurcation structures of single map. In particular, cluster-doubling bifurcation induced period-doubling bifurcations and clustering induced chaos are found. At the onset of multiple-cluster states, equal-site-occupation-partition, and consequently, equal-phase-shift states (the so-called antiphase states reported previously, Phys. Rev. Lett. 65, 1749 (1990)) are always identified numerically.

chao-dyn↗

arXiv1993

Linear Response Theory in Stochastic Resonance

The susceptibility of an overdamped Markov system fluctuating in a bistable potential of general form is obtained by analytic solution of the Fokker-Planck equation (FPE) for low noise intensities. The results are discussed in the context of the LRT theory of stochastic resonance. They go over into recent results (Gang Hu et al {\em Phys. Lett. A} {\bf 172}, 21, 1992) obtained from the FPE for the case of a symmetrical potential, and they coincide with the LRT results (Dykman et al, {\em Phys. Rev. Lett.} {\bf 65}, 2606, 1990; {\em JETP Lett} {\bf 52}, 144, 1990; {\em Phys. Rev. Lett.} {\bf 68}, 2985, 1992) obtained for the general case of bistable systems.

chao-dyn↗