M.I. Sobhy

Methods of attacking chaotic encryption and countermeasures

Methods of attacking chaotic encryption algorithms have been developed. These methods have been applied to all the published chaotic encryption systems and all these systems are broken in very short computer times. Counter measures have also been developed in order to make chaotic encryption secure. Several examples and results are given.

UWB wearable button antenna

A UWB antenna based on button structures will be presented in this paper. The antennas use the wearable metallic button features and its bandwidth characteristics to create body-centric UWB monopole antennas. The antenna resulted is a rigid wearable antenna structure which is able to operate within the 3.1 GHz to 10.6 GHz bandwidth required for UWB communication systems. Good omni-directional pattern were obtained for the antenna which is desirable for transmission with other wearable devices located across the body.

Chaotic algorithms for data encryption

A system of encryption based on chaotic algorithms is described. The system is used for encrypting text and image files for the purpose of creating secure data bases and for sending secure e-mail messages. The system is also implemented on an FPGA for real-time applications. Levels of security several orders of magnitude better than published systems have been achieved.

SECURE COMPUTER COMMUNICATION USING CHAOTIC ALGORITHMS

In this paper the application of chaotic algorithms in sending computer messages is described. The communication is achieved through email. Other transmission media can also be used. The algorithm has a degree of security many orders of magnitude higher than systems based on physical electronic circuitry. Both text, image or recorded voice messages can be transmitted. The algorithm can be used for computer communication and for secure databases.

The design of microwave monolithic voltage controlled oscillators

The paper describes a complete design procedure for a monolithic microwave VCO. The procedure includes a computer simulation of the nonlinear active circuit. Practical implementation of the designed circuit and measured results are given.

Compuier-Aided Design of Microwave Integrated Circuits

This paper describes a general computer program for the analysis and design of passive, active and non-linear lumped/distributed circuits. This program is particularly suitable for the analysis of active microwave networks and GaAs integrated circuits.

A general interface between TLM models and lumped element circuit models

We describe the interfacing of transmission line matrix models of distributed microwave circuits with lumped element models. The lumped element circuits are connected with the distributed circuit via a line guiding only its fundamental TEM mode. The distributed circuit is modeled by the transmission line matrix (TLM) method. From the method of moments foundation of TLM it follows that the electromagnetic field can be expanded in subdomain base functions. The location of the transverse boundary surface between the TLM model and the TEM line is chosen at a location where the evanescent higher modes have completely decayed. Mode matching theory is applied for computation of the scattering matrix between the TLM lines and the TEM line. The interfacing between distributed circuits and lumped element circuit is discussed for the case of a lumped nonlinear diode and a lumped element generator embedded in a microstrip circuit. The microstrip circuit is modeled via TLM whereas the lumped element models are described by the state space approach.<<ETX>>

Lorenz chaotic model using Filed Programmable Gate Array (FPGA)

In this paper, we introduce a new method to implement chaotic generators based on Lorenz chaotic system given by the state equations by using Filed Programmable Gate Array (FPGA). The aim of this method is to increase the frequency of the chaotic signals. The new method is based on MATLAB/sup /spl reg// Software, Xilinx System Generator, Xilinx Alliance tools, Leonardo spectrum or Synplicity Synplify and ModelSim XE PLUSE. The toolbox of the Xilinx System Generator used as toolbox under MATLAB/sup /spl reg// Simulink toolbox to convert any MATLAB/sup /spl reg// Simulink model to the Xilinx System Generator model then to generate the VHDL code for that model. The hardware can be used directly in chaotic communication systems with high frequency.

Detection of radar target pulse in the presence of noise and jamming signal using the multiscale wavelet transform

This paper presents an efficient method to identify the received target pulse in the presence of the noise and received false jamming signal. The multiresolution property of the wavelet transform is well suited to analyzing such multiscale signals. Local maxima of the wavelet transform enable us to detect the location of the target pulse edges. The algorithm introduced in this paper is based on the correction and integration of the local maxima of the wavelet coefficients. This gives a good method to discriminate the true reflected target pulse from the false ones.

Parallel processing application to nonlinear microwave network design

A powerful algorithm developed for analyzing nonlinear microwave networks using parallel processors is described. The system offers the possibility of analyzing and optimizing these circuits using low-cost desktop computers and eliminates the need for workstations or mainframes. The developed programs run on a desk top with a transputer board capable of concurrent processing speeds of over 40 MIPS (million instructions per second). A new representation of microwave and nonlinear circuits has been developed to suit the required parallelism. By identifying every circuit element with a process, efficient optimization is feasible. Applications to the analysis of nonlinear amplifiers, frequency multipliers, and microwave mixers are described. >