مجله علوم و فناوری های پدافند نوین
سال دهم شماره 4 (پیاپی 38، زمستان 1398)

In this paper, a novel low-profile switchable narrow and wide band circular ring sector slot antenna is presented for wireless applications. Adjustable operating frequencies especially with the ability of switching between narrow and wide band modes could provide considerable immunity from jamming and noises. The combination of two wideband and six narrowband modes are provided using PIN diode switches inserted on the relatively wide slot. The slot is etched in the ground plane with the size of 33×36 mm2. The results show the operating frequency bands of 3.47-5.48 GHz for the first wideband operation and 5.2-7.37 GHz for the second wideband operation with S11<-10 dB. In narrowband modes, the operating frequencies can be adjusted from 2.58-3 and 4.88-5.5 GHz for the first (f1) and second (f2) resonances, respectively. The proposed antenna is suitable for applications such as WLAN IEEE 802.11a (5.1 to 5.8 GHz), WiMAX (2.5–2.8 GHz), the ultra wideband (UWB) sub-band groups (3.5–5 GHz and 5–6.5 GHz) and also C-band radars.

Long-Range-Navigation (LORAN) pulse generator is an essential part of ground-based Local Positioning System (LPS) that provide a specific standard waveform. There are several solutions for design and implementation of the pulse generator. Switching amplifiers using Pulse-Width-Modulation (PWM) technique is one of the solutions that can be used for this purpose. In this paper, the simple PWMwas modified to a multi-level PWM and its optimum levels are extracted to provide a high power LORAN transmitter.  Multi-level PWM provides essential standards of LORAN pulse waveform. In order to provide a transmitter with 1MW power, three- to- eleven levels of PWM using 16 Class D amplifiers has been considered. At constant conditions, such as power and number of amplifier modules, the requirements and specifications of transmitter have been simulated. Simulation results show that in the best case, using eleven levels for PWM,the maximum zero crossing error in the 4th to 12th half-cycle is 16.6 ns and the bandwidth of provided pulse is 5 kHz. Moreover, MMSE and maximum error of peak points in the first eight half-cycles are 0.009 and 0.021 respectively, which are appropriate standards of a LORAN transmitter.

Today, the researchers are interested to radio frequency based localization methods such as Time Of Arrival (TOA), Time Difference Of Arrival (TDOA), Angle Of Arrival (AOA), Received Signal Strength Indication (RSSI) and their combinations. In sensor networks such as the base station cellular network, time-based methods for positioning are used. For security purposes, standards have been written in order to improve the accuracy of positioning in mobile networks. One of the factors influencing positioning accuracy is the placement of the localizer receivers. In this paper, a solution to improve the accuracy of the positioning is suggested by comparing the two principal methods based on time, i.e., the time of arrival of the signal and the time difference of the signal arrival, and the separation of the noise quantity into two normal and abnormal parts. In fact, by examining the abnormal noise and calculating this amount at the desired area for positioning, the appropriate method for positioning in the sub-sections is determined and the positioning is achieved.

Blind recognition of error correction codes parameters from intercepted bit-stream at the receiver side, is highly considered in military and commercial applications. In fact, identification of the encoding scheme used in the transmitter without any prior information, is a challenging task to the adversary. Several methods have been presented for blind code recognition. In this paper, a statistical method for recognition of  the length of the code word and the length of the block of information is presented. This scheme not only is resistant to error, but also its performance sustains in long codes. In this work, the method has been tested using some clustering algorithms such as K-Means and Jenks Natural Breaks. Then, a novel method to extract features of systematic binary linear block codes has been presented. Simulation results in MATLAB show that the proposed method, in addition to having low computational complexity and high performance rate, have an acceptable result in identifying systematic block codes with long lengths and even at high error levels.

Since multiple memory accesses are time consuming, processors use cache to optimize runtime. The cache leads to temporal changes in the implementation of a program and is one of the most important source of information leakage in the timing side channel. Flush+Reload attack is a series of Cache Side Channel attack that the most important characteristics of this attack can be used to identify access to a particular memory line and target being the lowest level cache (LLC) noted that these features lead to increased precision of attack and its usability. In this paper, a new Flush+Reload attack (of the chosen plaintext attack) on the AES implemented in the OpenSSL is presented. While the previous Flush+Reload attack on AES requires about 400000 encryption operations, the attack presented in this paper, required only about 100 encryption operations to fully recover encryption keys. The attack described in this paper is implemented in practice and the actual results confirm the attack’s integrity.

Malwares have grown drastically in recent years. Furthermore, the behavior of the newly produced malwares are getting more complex and shrewd. This paper present malware detection methods and especially focus on code and DLL injection attacks. Novel malwares try to obfuscate and hide their behavior through the injection of malicious code in allocated memory and binary file of trusted applications. By data mining on massive volume of malwares, the proposed method of the paper derive chain of API calls through installing logger hook at the kernel space of the operating system in order to model the malicious behavior of code/DLL injection based on linear regression function. The proposed method use association rules machine learning based on Apriori algorithm for early detection of attacks and is able to prevent completion of the attack by blocking remote thread creation. Finnaly, the accuracy of the proposed method is evaluated using dataset from valid references and the results are compared with available Antivirus tools under the same conditions. Results of the evaluation indicate that the proposed method can recognize code/DLL injection attacks by the accuracy of about 94%. Moreover, success coefficient of the proposed self-defense system is evaluated of 88.88% against real code/DLL injection attacks.

matrices are one of the most important components in designing block ciphers. Based on the hardware terminologies, the acceptable speed of the implementation of  matrix and its inverse is one of the main features of  matrix for  structures. In this paper, a new type of binary block matrices called semi involutory is used such that the cost of implementation of these matrices and their inverses are equal. At first, by using binary linear functions over binary sparse matrices, a semi involutory matrix is proposed so that the cost of implementation of the proposed matrix is  bitwise  for  bit input. The structure of proposed matrix and its inverse are based on the structures, so they have suitable implementation from hardware point of view. Next, a semi involutory  matrix is proposed by applying structures such that the proposed  matrix is implemented with the bitwise  for  bit input. The proposed semi involutory  matrix is the major result, since the best known result in the implementation of a semi involutory  matrix for 8 bit input, based on the heuristic algorithm, is  bitwise  while  bitwise was obtained in this research. Moreover, the proposed  matrix is implemented with    for  bit input by applying suitable binary sparse matrices.

In the last decades, due to the emergence of new technologies, the usage of multi-energy systems has been widely increased. Therefore, it is very necessary to model and assess the maximum energy supply for consumers. Also, maintenance and development of resources and infrastructures against natural disasters and external threats become very essential in sustainable development programs. Recently, due to the severe dangers of climate change, as well as external threats, such as terrorist attacks, there has been a potential increase in power outages, which illustrates the value and importance of improving the resilience of energy systems. In this paper, a military center has been considered as a multi-energy microgrid. In this test system, the infrastructure of different energy carriers like gas and electricity has been used to provide the required amount of energy in the event of an attack, as well as to increase the security and resiliency of the multi-energy system.Also, the resiliency index is used for passive defense purposes to provide accurate estimation of energy security for a military center.

Excavation of underground spaces provides locality for military and defence application. The stability of the excavation wall is one of the important issues in the field of geotechnics. The use of steel anchor elements is one of the sustainable methods for stability of excavation walls. These anchors pin the surface of the wall to the back soil, providing the wall's stability. In this research, the behavior of soil nailing, anchored walls and their combination against the blast load has been modeled by Abaqus finite element software. Also reinforcing elements are placed in different walls so that the safety factor becomes 1.5. Different numerical models are chosen to determine the best plan for dealing with the dynamic load caused by the explosion. The explosive charge in software is equivalent to the 120 kg TNT explosion, and this load is applied at a distance of three times of the depth to excavation. Also the modeling of full anchored wall has been verified in static mode. Based on the results, the deformation of the top of the wall after the explosion increased by 5 to 65 times of those before the explosion in various models and the primitive deformation caused by static load increased after excavation. In a wall that was completely reinforced by nails, static analysis showed the highest amount of deformation, but after the explosion, the wall reinforced by the combination of anchors and nails showed the most deformation. The safety factor of the nailing wall before the explosion was 1.5 and then reached to 1.01. The explosion also caused a 110% increase in tensile stress of the Anchors.

Rapid foundation should be movable, low weight and high strength to be used in critical situations. In this study, steel foundation is discussed due to high ductile and strength. Thus, steel plate and pile system is evaluated by plaxis 3d foundation and parameters of length (L), number of steel piles (N), thickness (t) and dimensions of plate (B) are studied. The Mohr Coulomb was used to model soil behavior and steel piles and plates in dimension of 200, 300 and 500 mm were evaluated. The results show that area ratio of pile to plate (AS) is affected by bearing capacity and settlement reducing. In this study, while the area ratio of pile to plate is more than 5%, the bearing capacity ratio (BPI) has increased with increasing length, diameter and number of piles. Whereas, the BPI of plate in dimension of 200*200 mm and 500*500 mm in single pile mode to four pile mode ratio is increased from 1.01 to 1. 8 and 1.01 to 1.15, respectively.