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

Recent Advances in Magnetoencephalography

The review of novel advances in the magnetoencephalography (MEG) technique is present, including the development of optically pumped magnetometers (OPM) which are very promising for brain-computer interfaces (BCIs). The main advantage of OPMs over conventional SQUID devices is that they do not require cryogenic cooling, that decreases their price by 2–3 times. Moreover, the OPMs can be placed within millimeters from the scalp, that approximately doubles the signal-to-noise ratio. In addition, they are not so susceptible to muscle artefacts as EEG. In addition, the location of OPMs in a field-nulling apparatus decreases the influence of artefacts caused by head movement in the ambient field. All these advantages give potential possibilities to develop a new generation of OPM-based BCIs, cheaper, more flexible and sensitive than SQUID-based BCIs, which can serve for both motor and non-motor tasks. Despite the enormous progress made in the past few years, OPM–MEG is so far a developing technology that needs further improvement. Due to their large size, the number of channels is relatively small and therefore they cannot cover the entire head. The miniaturization and universality of lightweight helmets would be an essential step towards further development of OPM wearable for BCI applications

Stochastic Analysis and Control in Kinetics of Multistable Chemical Reactor

We consider a model of thermochemical reactor proposed by Nowakowski. Stochastic effects in the bistability zone are studied. A parametric analysis of noise-induced transitions between coexisting equilibria is carried out on the basis of the stochastic sensitivity technique and confidence ellipses method. We solve the problem of stabilization of the equilibrium regime under incomplete information. The feedback regulator which reduces the stochastic sensitivity and stabilizes the randomly forced equilibrium is constructed. © 201

Dynamics of a ring of three unidirectionally coupled Duffing oscillators with time-dependent damping

We study dynamics of a ring of three unidirectionally coupled double-well Duffing oscillators for three different values of the damping coefficient: fixed dumping, proportional to time, and inversely proportional to time. The dynamics in all cases is analyzed through time series, Fourier and Hilbert transforms, Poincar\'e sections, as well as bifurcation diagrams and Lyapunov exponents with respect to the coupling strength. In the first case, we observe a well-known route from a stable steady state to hyperchaos through Hopf bifurcation and a series of torus bifurcations, as the coupling strength is increased. In the second case, the system is highly dissipative and converges into one of stable equilibria. Finally, in the third case, transient toroidal hyperchaos takes place

Multistability and stochastic phenomena in a randomly forced thermochemical system

A model of the thermochemical reactor with well mixing is considered. An impact of random noise on the attractors of this model is studied in zones of saddle-node bifurcations with transitions from mono- to bimodal dynamics. Phenomena of the stochastic excitability and noise-induced transitions are demonstrated. Critical values of the noise intensities corresponding to the onset of generation of the large-amplitude stochastic oscillations are estimated

Multistability and stochastic dynamics of Rulkov neurons coupled via a chemical synapse

We study complex dynamics of two Rulkov neurons unidirectionally connected via a chemical synapse with respect to three control parameters: (i) a parameter responsible for the type of dynamical behavior of a solitary neuron, (ii) coupling strength, and (iii) noise intensity. The coupled system exhibits various scenarios on the route from a stable equilibrium to chaos with respect to the coupling strength. We observe a variety of dynamical regimes, including mono-, bi- and tri-stability, order-chaos transitions and vice versa, as well as the coexistence of in-phase and anti-phase synchronization. We also study transitions between in-phase and out-of-phase synchronization with statistics on the duration of synchronization intervals and transitions from order to chaos. In addition to numerical simulations, we demonstrate the effectiveness of the analytical confidence ellipses method based on stochastic sensitivity approach. © 2023 The Author(s)Russian Science Foundation, RSF: 21-11-00062The work was supported by the Russian Science Foundation (project No. 21-11-00062)

Autonomous Bursting in a Homoclinic System

A continuous train of irregularly spaced spikes, peculiar of homoclinic chaos, transforms into clusters of regularly spaced spikes, with quiescent periods in between (bursting regime), by feeding back a low frequency portion of the dynamical output. Such autonomous bursting results to be extremely robust against noise; we provide experimental evidence of it in a CO2 laser with feedback. The phenomen here presented display qualitative analogies with bursting phenomena in neurons.Comment: Submitted to Phys. Rev. Lett., 14 pages, 5 figure

Stochastic phenomena in pattern formation for distributed nonlinear systems

We study a stochastic spatially extended population model with diffusion, where we find the coexistence of multiple non-homogeneous spatial structures in the areas of Turing instability. Transient processes of pattern generation are studied in detail. We also investigate the influence of random perturbations on the pattern formation. Scenarios of noise-induced pattern generation and stochastic transformations are studied using numerical simulations and modality analysis. © 2020 The Author(s) Published by the Royal Society. All rights reserved.Russian Science Foundation, RSF: 16-11-10098Data accessibility. This article has no additional data. Authors’ contributions. All authors contributed equally. Competing interests. We declare we have no competing interests. Funding. The work was supported by the Russian Science Foundation (grant no. 16-11-10098)

Detecting specific oscillatory regimes in the dynamics of erbium-doped fiber laser

A method for determining the oscillatory mode occurring in an erbiumdoped fiber laser with a modulated parameter is proposed. The method is based on using a continuous wavelet transform with a mother Morlet wavelet and analyzing the energy of the wavelet spectrum that corresponds to the relevant range of time scales