Ioannis M. Kyprianidis

Image encryption process based on chaotic synchronization phenomena

This paper presents a novel image encryption scheme, which uses a chaotic True Random Bits Generator (TRBG). The chaotic TRBG is based on the coexistence of two different synchronization phenomena. The first one is the well-known complete chaotic synchronization while the second one is a recently new proposed synchronization phenomenon, the inverse π-lag synchronization. This coexistence is observed in the case of two mutually coupled identical nonlinear circuits. The nonlinear circuit, which is used, produces double-scroll chaotic attractors. The initial conditions of the coupled system and the values of the circuits parameters serve as the private key of the proposed cryptographic scheme. In order to face the challenge of using this chaotic TRBG in such cryptographic schemes, the produced bits sequence is subjected to statistical tests which are the well-known Federal Information Processing Standards-140-2. This bits sequence has then been used to encrypt and decrypt gray-scale images. Also, the security analysis of the encrypted image demonstrates the high security of the proposed encryption scheme. Highlights? We develop an image encryption scheme based on a chaotic random bits generator. ? The coexistence of synchronization phenomena is the main feature of this generator. ? The complete and the inverse π-lag are the observed synchronization phenomena. ? The nonlinear circuit, which is used, produces double-scroll chaotic attractors. ? The high security of the proposed encryption scheme is confirmed.

A chaotic path planning generator for autonomous mobile robots

This work presents a chaotic path planning generator which is used in autonomous mobile robots, in order to cover a terrain. The proposed generator is based on a nonlinear circuit, which shows chaotic behavior. The bit sequence, produced by the chaotic generator, is converted to a sequence of planned positions, which satisfies the requirements for unpredictability and fast scanning of the entire terrain. The nonlinear circuit and the trajectory-planner are described thoroughly. Simulation tests confirm that with the proposed path planning generator better results can be obtained with regard to previous works.

Experimental investigation on coverage performance of a chaotic autonomous mobile robot

In many autonomous mobile robotic missions the complete and fast coverage of the workspace, scanned by an unpredictable trajectory, plays a crucial role. To satisfy these special demands in the design of an autonomous mobile robot, a motion controller, based on the dynamical behavior of a known discrete chaotic system, the Logistic map, is presented in this paper. The proposed method is based on a microcontroller for realizing a chaotic random bit generator and converting the produced chaotic bit sequence, to the robots trajectory of motion. The experimental results confirm that this approach, with an appropriate sensor for obstacle avoidance, can obtain very satisfactory results in regard to the fast scanning of the robots workspace with unpredictable way.

Analysis, adaptive control and circuit simulation of a novel nonlinear finance system

In the last three decades a growing interest in developing nonlinear dynamical systems for economic models, displaying chaotic behavior has been developed. To this direction, a novel 3-D nonlinear finance chaotic system consisting of two nonlinearities is presented. The dynamical analysis of the proposed system confirms its complex dynamic behavior, which is studied by using well-known simulation tools of nonlinear theory, such as the bifurcation diagram, Lyapunov exponents and phase portraits. Also, some interesting phenomena related with nonlinear theory are observed, such as route to chaos through a period doubling sequence, antimonotonicity and crisis phenomena. In addition, an interesting scheme of adaptive control of finance systems behavior is presented. Furthermore, the novel nonlinear finance system is emulated by an electronic circuit and its dynamical behavior is studied by using the electronic simulation package Cadence OrCAD in order to confirm the feasibility of the theoretical model.

Synchronization Phenomena in Coupled Colpitts Circuits

In this work, the case of coupling (bidirectional and unidirectional) between two identical nonlinear chaotic circuits via a linear resistor, is studied. The produced dynamical systems have different structure, in regard to other similar works, due to the choice of coupling nodes. As a circuit, a modification of the most well-known nonlinear circuit that can operate in a wide range of radiofrequencies, the Colpitts oscillator, is chosen. The simulation and the experimental results show a variety of dynamical phenomena, such as periodic, quasi-periodic and chaotic behaviors, as well as anti-phase and complete synchronization phenomena, depending on the value of the coupling coefficient.

Chaotic synchronization of three coupled oscillators with ring connection

Abstract We study the evolution of three identical, resistively coupled with ring connection, nonlinear and nonautonomous electric circuits from nonsynchronized oscillations to synchronized ones, when they exhibit chaotic behavior. Phase-locked states are also observed, as the coupling parameter is varied. The system’s dynamics depends on the way of coupling (unidirectional or bidirectional).

Chaotic behaviour of a fourth-order autonomous electric circuit

Abstract The chaotic dynamics of a fourth-order autonomous nonlinear electric circuit was studied by measuring its response in the form of chaotic time series. The circuit consists of two active elements, one linear negative conductance and one nonlinear resistor exhibiting a symmetrical piecewise-linear v – i characteristic and two capacitances C 1 and C 2 , which serve as the control parameters of the system. From the experimental time series the minimum embedding dimensions m min =4, correlation dimensions ν , with positive noninteger values, and Kolmogorov entropies, tending to constant positive values, were determined by numerical evaluation for the examined states of the system.

Synchronization of two resistively coupled nonautonomous and hyperchaotic oscillators

Abstract We have studied the case of hyperchaotic synchronization of two resistively coupled nonautonomous and nonlinear identical electric circuits, using the frequency and the amplitude of the input signal as the control parameters. For low values of the amplitude the two circuits can be synchronized, but for higher values of the amplitude and frequency the possibility of synchronization depends on the coupled state variable. The onset of synchronization depends on the Lyapunov dimension of the individual electric circuit.

Fingerprint images encryption process based on a chaotic true random bits generator

In recent years, information security requires randomly selected strong keys. Most of the proposed methods provide keys, which are based on chaotic cryptographic algorithms. In this paper, a fingerprint image encryption scheme, based on a chaotic true random bit generator (TRBG), is proposed. The chaotic generator is based on a non-linear electronic circuit, which produces double scroll chaotic attractors. The initial conditions and the values of the circuit parameters serve as the private key of the cryptographic scheme. We use two chaotic generators with different initial conditions, which produce the bits sequences that XOR-ed for generating the final bits sequence. A well known statistical suite for testing the distribution of the bits sequence was adopted. This sequence has been used to encrypt and decrypt the fingerprint images. Also, the security analysis of the encrypted image demonstrates the high security of the proposed encryption scheme.

DYNAMICS OF TWO RESISTIVELY COUPLED DUFFING-TYPE ELECTRICAL OSCILLATORS

Duffing-type electrical oscillator is a second-order nonlinear electric circuit driven by a sinusoidal voltage source. The nonlinear element is a nonlinear inductor. We have studied the dynamics of two resistively coupled oscillators of this type in two cases. The first, when the oscillators are identical having chaotic dynamics, and the second, when the oscillators are in different dynamic states (periodic and chaotic, respectively). In the first case, chaotic synchronization is observed, while in the second case control of the chaotic behavior is achieved.