نشریه فناوری اطلاعات و ارتباطات انتظامی
پیاپی 4 (زمستان 1399)

Use of explosives by terrorist organizations has increased extensively in recent years. It is important to develop non-destructive and highly sensitive sensors to detect explosives. In this paper, a Photonic Crystal sensor using waveguides and nano cavities in a hexagonal network of silicon rods in the air substrate is proposed. Nano cavities are filled by an organic material with refractive index of 1.59. This two-dimensional Photonic Crystal sensor can detect two different explosives, RDX and HMX, simultaneously. The area of this symmetrical hexagonal structure is 19×17µm2. The FDTD method with plane wave propagation was used for analysis. Simulation is performed and the transmission spectrum of the structure is plotted. The entry of explosive in to the sensor causes the change of the refractive index. The maximum amplitude of the transmission spectrum at the output of two channels at 1590 nm has been increased due to the difference in the light absorption. Then, a difference of 0.03 in the maximum amplitude of the transmission spectrum is shown because of two different explosives. This feature is very useful for sensing and detection applications. Quality factor (Q factor ) for the designed sensor has been measured bout 122.28.

The global navigation satellite system is widely used in the guidance of military equipment, police. the quality of their receivers is very important due to low power level of these types of signals. In this paper, a continuous time wideband three-bit analog-to-digital quadrature delta sigma converter for a two-channel Global Navigation Satellite System (GNSS) receiver in different modes is designed. The proposed modulator is designed in FF structure. In the FF structure, there are two power hungry adders before the quantizer, which have been eliminated in the proposed design method. This action has reduced the number of op-amps, and as a result, has reduced the total power consumption of the modulator. The proposed modulator has a lower order of magnitude compared to similar modulators with the same bandwidth, and as a result has a lower number of op-amps, which reduces power consumption and also has more relative stability. This three-bit modulator is able to convert two separate channels with different bandwidths and in different modes up to 33 MHz bandwidth with a signal to noise ratio (SNR) of 64.8 dB at the same time as digital.

The purpose of this paper is to present a model based on neural networks with high accuracy to build a model for predicting violations based on factors such as a vehicle, human factors, environmental factors. Considering that in most studies, the role of the road and the vehicle have been considered more than in other cases, in this research, a model has been designed using various factors. The approach of this research is combined (quantitative, qualitative) and in terms of applied purpose and descriptive survey method, using multilayer model neural network (MLP) has been used. The effect of the transition on traffic violations has been studied so that the optimal model is selected and the three-layer model with high accuracy of 0.90483 is predicted as a model. The findings of this study indicate that human factors including gender, age, education, Occupation has the highest share of traffic violations and the three-layer model has better results and is more consistent with real data.

With the development of the electronic industry and the advent of modern processors, the attack model in the algorithms and encryption protocols also changed. In spite of computational complexity in algorithms and cryptographic protocols, implementations can be a factor for the leakage of confidential information. The attacker can attack when electronic components are executing the encryption operators using the secret key on sensitive data. As a result of computing, there is a leak of information in electronic components where attacks are called side-channel attacks. one of the most important sources of information leakage of side channels is time changes due to the execution of computation. The accesses to memory and the presence of branches in the program are expensive at runtime, so the processors use cache memory and branch- prediction to reduce this cost. Unfortunately, this optimization during execution leads to time changes in the execution of a program. The cache in the time side-channel attacks is more challenging and more practical. In this paper, we will review a variety of memory attacks on the implementation of the AES cipher algorithm. by implementing the attacks and comparing the results, we will extract and compare the security weaknesses of implementing the AES cipher algorithm against cache attacks.

With the development of new information and communication technologies and the pervasive use of cyberspace, distributed denial of service (DDoS) attacks are a serious threat to online organizations. These attacks can have destructive effects, for example, on one of its effects can be in terms of the public face of the trademark and its revenue. A good way to deal with DDoS attacks is to save a signature for each attack. Today, most organizations and institutions, both national and military (military and law enforcement) face such attacks, so in this study, while trying to identify intrusion detection systems in the proposed method to produce the necessary signatures to explain. Using this method, any attack can be detected as soon as this signature is found in traffic. However, this process is not easy and the signature production process is usually time consuming and requires a lot of effort. To help solve this challenge of generating signature problems, in this research, we propose an automated method for generating data-based signatures for DDoS attacks. This study also examines the relationships between different data packets of the same attack. In fact, data packet-based digital signatures are used for attacks whose pattern and core are the same, with only minor differences in the structure of the attack. The research concludes with a proposal for a signature generation algorithm and its validation using applied tools.

In this paper a novel branch line coupler with harmonic suppression and size reduction is designed. The proposed coupler is designed by using T-shaped lines, cross lines and open ended stubs. The presented coupler is designed at the operating frequency of 1.8 GHz, which can suppress up to fifth harmonic. Moreover, more than 78.5% size reduction is achieved, compared to the conventional coupler. In the other words the proposed coupler suppresses second, third, fourth and fifth harmonics with more than 15 dB, 27 dB, 24 dB, and 21 dB attenuation levels, respectively. The obtained insertion loss is less than 0.05 dB for both output ports. In addition, more than 28.3 dB and 27.9 dB return loss and output port isolation are obtained respectively. The designed coupler has a wide operating band from 1.67 GHz up to 1.93 GHz with center frequency of 1.8 GHz which shows 15% fractional bandwidth (FBW).