Alexander N. Pisarchik

Encryption and decryption of images with chaotic map lattices

We propose a secure algorithm for direct encryption and decryption of digital images with chaotic map lattices. The basic idea is to convert, pixel by pixel, the image color to chaotic logistic maps one-way coupled by initial conditions. After small numbers of iterations and cycles, the image becomes indistinguishable due to inherent properties of chaotic systems. Since the maps are coupled, the image can be completely recovered by the decryption algorithm if map parameters, number of iterations, number of cycles, and the image size are exactly known.

Optical Chaotic Communication Using Generalized and Complete Synchronization

We propose a secure optical communication system based on the principles of generalized and complete chaotic synchronization. A transmitter and a receiver both composed by two chaotic external-cavity semiconductor lasers are coupled in a master-slave configuration to provide generalized synchronization, while the master lasers in the transmitter and in the receiver are completely synchronized through the synchronization channel via an optical fiber. A message is added to the transmitter slave laser and sent to the receiver through the information channel to be compared with the output of the receiver slave laser. The system is robust to a small mismatch of the laser parameters or of the coupling between the master and slave lasers, unavoidable in a real system, and can even enable a good communication up to a 5 Gb/s transmission rate using the chaos masking encryption method, when the master laseres are coupled bidirectionally.

Experimental characterization of the bifurcation structure in an erbium-doped fiber laser with pump modulation

The bifurcation structure of phase space is investigated experimentally in an erbium-doped fiber laser with a sinusoidal pump modulation. We demonstrate a rich variety of bifurcations and dynamical states which appear in primary saddle-node bifurcations and discuss their relation to the main laser resonance. The systematic organization of coexisting attractors allows one to predict the behavior of the fiber laser, when initial conditions are allowed to evolve to their final states.

Control of multistability in a directly modulated diode laser

A semiconductor laser with modulated injection current has the property that many competing behaviors are possible and the system tends to alternate among them. Such a situation is not desirable if a stable output is required. We show with numerical simulations that additional slow harmonic modulation can annihilate undesirable coexisting attractors in this laser. We demonstrate great flexibility of the method in manipulating the lasers dynamics to select a desired behavior and even to make the system monos table.

Critical slowing down and noise-induced intermittency in bistable perception: bifurcation analysis

Stochastic dynamics and critical slowing down were studied experimentally and numerically near the onset of dynamical bistability in visual perception under the influence of noise. Exploring the Necker cube as the essential example of an ambiguous figure, and using its wire contrast as a control parameter, we measured dynamical hysteresis in two coexisting percepts as a function of both the velocity of the parameter change and the background luminance. The bifurcation analysis allowed us to estimate the level of cognitive noise inherent to brain neural cells activity, which induced intermittent switches between different perception states. The results of numerical simulations with a simple energy model are in good qualitative agreement with psychological experiments.

DYNAMICAL TRACKING OF UNSTABLE PERIODIC ORBITS

Abstract Tracking unstable periodic orbits and its stabilization by large periodic modulation of a control parameter are studied numerically in the Henon map and laser equations. Some important scaling relations linking the tracking range to the modulation amplitude and frequency are deduced. The results obtained with both models are compared. Experimental realization of dynamical tracking is demonstrated in a loss-driven CO 2 laser where cavity detuning or losses are periodically modulated.

Gray code permutation algorithm for high-dimensional data encryption

Abstract We present a novel permutation algorithm for fast encryption of a large amount of data, such as 3D images and real-time videos. The proposed P-Box algorithm takes advantage of Gray code properties and allows fast encryption with high information diffusion. The algorithm is optimized for integer q -bit operations ( q = 8 , 16 , 32 , … ), allowing a direct implementation in almost any hardware platform, while avoiding rounding errors of floating-point operations. By combining the P-Box with chaotic S-Box based on the logistic map, we design a complete, highly secure and fast cryptosystem.

Dynamic Effects of Submillimeter Wave Radiation on Biological Objects of Various Levels of Organization

We have presented an overview of the literature and of our experimental data on the influence of electromagnetic radiation in the submillimeter spectral region on biological objects of molecular, cellular, and organism levels. Possible physical mechanisms involved and the reasons for limited development of the research in this spectral range are discussed.

Increasing Blood Glucose Variability Is a Precursor of Sepsis and Mortality in Burned Patients

High glycemic variability, rather than a mean glucose level, is an important factor associated with sepsis and hospital mortality in critically ill patients. In this retrospective study we analyze the blood glucose data of 172 nondiabetic patients 18–60 yrs old with second and third-degree burns of total body surface area greater than 30% and 5%, respectively, admitted to ICU in 2004–2008. The analysis identified significant association of increasing daily glucose excursion (DELTA) accompanied by evident episodes of hyperglycemia (>11 mmol/l) and hypoglycemia (<2.8 mmol/l), with sepsis and forthcoming death, even when the mean daily glucose was within a range of acceptable glycemia. No association was found in sepsis complication and hospital mortality with doses of intravenous insulin and glucose infusion. A strong increase in DELTA before sepsis and death is treated as fluctuation amplification near the onset of dynamical instability.

Synchronization of coupled bistable chaotic systems: experimental study

We carried out an experimental study of the synchronization of two unidirectionally coupled Rössler-like electronic circuits with two coexisting chaotic attractors. Different stages of synchronization are identified on the route from asynchronous motion to complete synchronization, as the coupling parameter is increased: intermittent asynchronous jumps between coexisting attractors; intermittent anticipating phase synchronization; and generalized synchronization in the form of subharmonic entrainment terminated by complete synchronization. All these regimes are analysed with time-series, power spectra and phase-space plots of the drive and response oscillators. The experimental study implicitly confirms the results of numerical simulations.