فصلنامه پدافند غیرعامل
سال دوم شماره 3 (پیاپی 7، تابستان و پاییز 1390)

As far as threats of detection and targeting are concerned, countermeasure technology which meanscamouflage, concealment and decoy (CCD) and also its related materials have been subject to change and improvements proportional to the world technologie's improvement and development. There is a gap between our country's current CCD technologies and the world's state-of–the–art CCD ones. In order to eradicate this problem and reach the border of these technologies and take short cuts for achieving future scientific knowledge, it is necessary to be foresighted and observant about these kind of technologies properly. In the present study, in order to predict trend of future CCD technologies for several next years efforts has been made to use a combination of some conventional ways of future- researching such as scenario planning, environmental scanning, patent analyzing, relevance tree, morphological analysis, interactions and the methods of future cycle. Among obtained results and important trends, some of specifications of CCD products such as their lightness, spectral expansion, multifunctional, smart and dynamic capabilities can be mentioned using prerequisite and …… technologies like nano, bio, MEMS, NEMS.

Investigation of ionospheric layer and prediction of its behavior (against external factors) can be an important step in the reduction of environmental, properties and human damages due to intentional variation in this region. For better understading of this layer and controlling the situation before critical condition, many experimental and theoretical investigations are required. One way of understanding ionospheric parameters is variation of collision frequency of electrons with neutral particles. In this paper two types of collision frequencies are calculated for electrons colliding with N2, H2, O2, CO2 and CO gases as functions of temperature. Also electron mobility is computed for these gases and the results are compared with those of experimental and theoretical works.

The Need to modern and reliable communication systems, seems to be more important, as the probability of society chaos, terrorist threats and natural disasters increase. These communication tools should be able to transmit, within the shortest possible time, the vital and emergency messages from crisis- stricken regions to control and management centers and from there, to endangered and relief needing people so that their lives and properties could be protected against accidents and disasters or the damage rate could be mitigated. One of the most important features of these systems is that they are able to act well under severe conditions and that their performance are not intentionally and unintentionally vulnerable. Wireless sensor networks are one of the most advanced technologies for such cases. Key management has remained a challenging issue in wireless sensor networks (WSNs) due to the constraints of sensor node resources. Various key management schemes that trade off security and operational requirements have been proposed in recent years. In this article, we first examine the security and operational requirements of WSNs and then review eight key management protocols: Eschenauer,q-composite,Yener, Du, LEAP, SHELL, Panja, and Yang and analyze them in the case of security and operational requirements. Finally we propose some proposals for selecting a suitable protocol.

The implementation of a secure and resistant communication system into the electronic warfare menaces, have always been a part of main challenges in military communications. The high frequency, high capacity of data transmission and also direct line of sight of optical waves have changed Free-Space Optical communication systems, into a popular technology in defensive and military uses but, the performance of a FSO communication link could be severely degraded due to atmospheric turbulence, which causes random fluctuations of the phase and the amplitude of the received signal. Both the aperture averaging technique and different modulation formats can mitigate the impairments of atmospheric turbulence. The purpose of this paper is to study and compare the Bit-Error-Rate (BER) performance of several modulation formats under different atmospheric turbulence scenarios with aperture averaging technique. The simulation results show that the aperture size is so effective in strong turbulence and the achieved performance improvement by aperture averaging is more significant for M-ary PPM [M>2] modulation, than other formats such as OOK, DPSK.

The widespread application of nuclear, biological and chemical agents in wars and terrorist attacksthroughout past twenty years has displayed that the threat of such agents still exists and is increasing as well. At present, the advanced and new NBC doctrines proposed in 2002 in western countries especially among NATO members, have usually three different levels as follows [1,2,3]: counterforce active defense passive defenseIt is noteworthy to mention that NATO, in its new doctrine, has followed the "passive defense" approach regarding weapons of mass destruction (WMD). But some of the NATO membering countries, especially America and England, make use of another approach. The "deterring force" is based on strengthening international Nuclear non-Proliferation Treaties (NPT) and protocols of weapons of mass destruction and using different leverages to prevent the advent of NBC weaponsrelated technologies (or their development) to certain countries [1,2,3]. The passive defense approach in countering NBC weapons of mass destruction is based on the following three principles:1. contamination avoidance (detection, reporting and warning)2. protection and safety against modern warfare agents3. decontamination of modern warfare agentsIn this article, the approaches of different countries to counter NBC weapons have been reviewed using descriptive study method and is based on the assumption that enemy's deterrence of modern warfare weapons application is largely dependent on the effective preparedness of defense forces. Another important factor which can play a role in deterrence is achieving a high level of science and technology to increase the defensive capabilities against modern warfare weapons. Moreover, by reviewing the principles of modern warfare passive defense including detection and measurement, protection and safety and decontamination, we will present the effects of vulnerability mitigation of these principles against NBC modern warfare weapons, as well.

Communication networks as one of the country's critical infrastructures are considered as testbeds for various communication applications and its use is increasing rapidly. Due to lack of security in communication networks along with the undeniable benefits, serious and irreparable challenges would be created in the country. Comprehensive understanding of network security problems and measures to overcome the major problems in this area, a significant role in the convention to promote security, safety and sustainability of infrastructure and communications will play a major step toward securing the objectives of passive defense in this regard. One of the most important types of stream ciphers are symmetric encryption algorithms that are appropriate to the specific features and in some applications such as network security and telecommunications infrastructure, the security assessment is an important consideration in the areas of passive defense and international project eSTREAM in line with increased activity in this branch of cryptography can play an important role. This article, cryptanalyzes one of the stream ciphers based on array rolling with distinguishing attack. The main idea of introducing a distinguisher on HC-256'. In this attack we need about 2556 linear equations involving binary keystream variables.

In order to decrease the damages of substructures and important operational structures againstweapons of an enemy, they will be transferred into appropriate depth of the ground and the onlycommunication way of these spaces with external environment are their ingress and egress and incase of damage, communication with external environment will be disconnected and people andequipments inside the safe space will be captured. Therefore these inputs should be designed insuch a way which can reduce explosion waves and prevent these waves from entering the underground safe spaces. The purpose of this paper is to explain weak and strong points of differentmethods of decreasing explosion waves in entrance safe spaces. In this research, different types ofdecreasing explosion effects on entrance of underground safe spaces are reviewed through applyingdescriptive methods and library research and by content analysis, weak and strong points aregained. Finally, it is concluded that applying one method may not be enough and we can utilizesome other methods.