Security enhancement for A5/1 without losing hardware efficiency in future mobile systems

A5/1 is the strong encryption algorithm which protects the air interface of the GSM cellular network. However, in the Fast Software Encryption Workshop 2000 two attacks, the biased birthday attack and the random subgraph attack against A5/1 were presented [1]. In this paper, we propose new security enhancements to improve A5/1 encryption algorithm from the biased birthday attack [1] and random subgraph attack [3] [4] in order to be used in future mobile communication systems. The improvements that make both attacks impractical are based on the clocking mechanism of the registers, and their key setup routine. Furthermore, we have increased the linear complexity of A5/1 to make the solution of the linear equations [2] impractical in real time systems. Finally, both original and modified versions of A5/1 were implemented easily in a CPLD device for 3rd generation mobile systems

Two new approaches to spatial interpolation with inherent sidelobe suppression for imaging riometers

Absorption images as obtained by imaging riometers such as IRIS are usually created by interpolating between absorption values for individual beams. For IRIS, the locations of the beam centres serve as grid points for subsequent linear interpolation. Although generally producing good results, the fact that the actual shape of the imaging beams is not considered, potentially introduces errors and can lead to misinterpretations. In this paper, two alternative interpolation methods are introduced. Method A is based on measuring the similarity between simulated reception of individual point sources and actually received data. Method B uses a mathematical model of the sky brightness distribution parametrised by the received data. All interpolation methods are applied to power data, as opposed to absorption data, in order to avoid any errors that might be introduced by intermediate processing steps, especially QDC (quiet-day curve) generation. We apply all methods to synthetically generated test data as well as to three exemplary real datasets which are also compared to a calculated sky brightness distribution obtained from a skymap

Application of Space-Time Diversity/Coding For Power Line Channels

The purpose of the present work is to evaluate the application of space-time block codes to the transmission of digital data over the power-line communication channel (PLC). Data transmitted over the power-line channel is usually corrupted by impulsive noise. In this work we analyse the performance of space-time block codes in this type of environment and show that a significant performance gain can be achieved at almost no processing expense

Simulation of high energy tail of electron distribution function

This report presents Monte Carlo simulations of the electron energy distribution for alow ionized plasma interacting with the F-region neutral gas. The results show a depletion in theelectron distribution above 2 eV between 10 and 80 %, decreasing with altitude. The depletion ismainly due to electron energy loss to . This micro-physical energy transfer model gives goodagreement with optical observations of enhanced emissions from at 6300Å and EISCATUHF measurements of electron cooling during HF radio wave heating experiments. Someimplications for incoherent scatter spectra are derived. The results suggest that a weak(approximately 1000 times weaker than the ion-line) and wide (2 MHz) peak around +-1 MHz fromthe ion-line in the EISCAT VHF incoherent scatter spectrum should be a consequence of theelectron-neutral interaction

Cross correlations of Frank sequences and Chu Sequences.

Sets of Frank sequences and Chu sequences are two classes of polyphase sequence with ideal periodic autocorrelation functions, which at the same time have optimum crosscorrelation functions. The authors consider the crosscorrelations of sets of combined Frank/Chu sequences, which contain a larger number of sequences than either of the two constituent sets. It is shown analytically that the crosscorrelations are similar to those of the original sets with one exception, while the autocorrelations remain perfectly impulsiv

A GPU-accelerated finite-difference time-domain scheme for electromagnetic wave interaction with plasma

A GPU-accelerated Finite-Difference Time-Domain (FDTD) scheme for the simulation of radio-frequency (RF) wave propagation in a dynamic, magnetized plasma is presented. This work builds on well-established FDTD techniques with the inclusion of new time advancement equations for the plasma fluid density and temperature. The resulting FDTD formulation is suitable for the simulation of the time-dependent behaviour of an ionospheric plasma due to interaction with an RF wave and the excitation of plasma waves and instabilities. The stability criteria and the dependence of accuracy on the choice of simulation parameters are analyzed and found to depend on the choice of simulation grid parameters. It is demonstrated that accelerating the FDTD code using GPU technology yields significantly higher performance, with a dual-GPU implementation achieving a rate of node update almost two orders of magnitude faster than a serial implementation. Optimization techniques such as memory coalescence are demonstrated to have a significant effect on code performance. The results of numerical tests performed to validate the FDTD scheme are presented, with a good agreement achieved when the simulation results are compared to both the predictions of plasma theory and to the results of the Tech-X® VORPAL 4.2.2 software that was used as a benchmark