Air-gap System Research Articles

HydraulicBridge: Covert Signaling Channel between Air-Gapped Systems Using Hydraulic-Pressure Fluctuations

To protect critical computing systems from network attacks, modern enterprises typically employ physical isolation measures to disconnect them from open networks such as the Internet. However, attackers can still infiltrate these closed networks through internal employees or supply chain vulnerabilities. This presents the primary challenge that attackers face: how to effectively manage and manipulate infected devices that are isolated from the external network. In this paper, we propose a new covert communication technology called HydraulicBridge, which demonstrates how air gap networks can communicate through covert water pressure-fluctuation channels. Specifically, we demonstrate how water pressure from water pipes can be used to communicate with infected hosts within an air gap network. Additionally, we provide experimental results demonstrating the feasibility of covert channels and test the communication speed in the experimental environment. Finally, we offer a forensic analysis and propose various methods for detecting and blocking this channel. We believe that this study provides a comprehensive introduction to previously unseen attack vectors that security experts should be aware of.

Electrical discharge reproduction in rod-barrier-plane system

The present paper deals with new modeling to reproduce the electric discharge in the rod-plane air gap system with rubber insulating barrier under AC and impulse voltage. This model considers the randomness character of discharge evolution which is governed by the electric field. The discharges shape obtained by this model are compared with ones given by experimental tests. The established model reproduces correctly the forms of discharges obtained by experimental tests under AC voltage. It is found that the behavior of the electrical discharge depends not only on the dimension (thickness and width) of the insulating barriers but on its positions in the air gap as well. It is to highlight that the mode of applied voltage is of key importance barrier. Experimental investigation shows that the developed arc can evolve on 1 to 4 channels. The generated discharges in AC voltage distinguish by the formation of a multiple-channel arc. Whereas, the discharge under lightning impulse voltage found to progress in a single channel whatever the barrier position and dimensions. The model confirms that electric field is the most important factor in the behavior of the rod-insulating barrier-plane system submitted to high voltage.

Multi-coil wireless power transfer (WPT) technique for boosting efficiency in large air gap systems

An energy-efficient high-powermulti-coil wireless power transfer system (WPT) has been studied in this paper. The proposed system was first analyzed and examined using theoretical modeling; this was followed by finite element analysis and circuit simulation to confirm the goal. As the air gap between the transmitter and receiver coils widens, the coupling coefficient of a WPT system will drop. A large-air-gap WPT system’s coupling coefficient can be raised by adding relay coils between the transmitting and receiving coils. On the other hand, an increased coupling coefficient improves the system’s overall power transfer efficiency. The suggested multi-coil system, which has an air gap of 15 cm and a lateral misalignment of 3 cm between the transmitting and receiving coils, has been simulated and verified using the Maxwell 3-D finite element tool and Ansys Simplorer circuit simulation software.

Analysis and Research on No-Load Air Gap Magnetic Field and System Multiobjective Optimization of Interior PM Motor

In this article, considering the influence of iron core saturation and complex boundary conditions, a novel no-load magnetic field analytical method and system multiobjective optimization model for interior permanent magnet synchronous motor (IPMSM) are proposed. First, an analytical method based on magnetic potential permeance method is proposed. The complex cogging effect and equivalent air gap permeability function are fully considered in this method. Furthermore, on the basis of Taguchi optimization design based on Fuzzy theory, an improved optimization model considering multivariable interaction is proposed. Among them, in order to comprehensively consider the performance of electromagnetic, vibration, and temperature rise, five optimization objectives including torque, pulsation, cogging torque, loss, and flux density are optimized. The sensitivity of design variables and the interaction between variables are not ignored. Finally, a 6-pole 36-slot IPMSM is manufactured for prototype experiments. A large number of prototype experiments, finite element, and computational fluid dynamics simulation analysis including no-load magnetic field, back electromotive force, temperature rise, electromagnetic torque, and so on are carried out. The accuracy and rationality of the proposed no-load magnetic field analysis method and global optimization model are well-verified.

Alternating current flashover voltage of a uniform polluted glass flat insulator under parallel electric discharges effect

<span>This work presents a study aiming to analyze the development of parallel discharges on insulating surfaces of different sizes uniformly polluted. Moreover, it is aimed to find an equivalence between multiple point-point and plane-plane configurations. The study is carried out under alternating current (AC) voltage. The effects of many parameters on the electric strength of the considered air gap system configurations are presented. These parameters are the length of the creepage distance, the pollution degree and the contaminated surface width. Glass rectangular surface are used for the tests. Finally, a video camera system is used to support this investigation by laboratory observations of the full process of flashover mechanism. The obtained results show that there is a width limit approximately equal to 8 cm beyond which several arcs, parallel, consecutive and independent can <span>develop. This limit represents the minimal electrical performance of the insulation and we did not observe any effect of the volume conductivity on it.</span></span>

Air-gapped networks: the myth and the reality

On the face of it, air-gapped computer systems seem to offer airtight protection from a cyber security standpoint. After all, being physically isolated from unsecured networks like the public Internet and local area networks should mean that a computer network is wholly inaccessible to remote threat actors. But are they as secure as most people think?

MAGNETO: Covert channel between air-gapped systems and nearby smartphones via CPU-generated magnetic fields

This papers shows that attackers can leak data from isolated, air-gapped computers to nearby smartphones via covert magnetic signals. The proposed covert channel works even if a smartphone is kept inside a Faraday shielding case, which aims to block any type of inbound and outbound wireless communication (Wi-Fi, cellular, Bluetooth, etc.). Malware is implemented to control the magnetic fields emanating from the computer by regulating workloads on the CPU cores. Sensitive data such as encryption keys, passwords, or keylogging data is encoded and transmitted over the magnetic signals. A smartphone located near the computer receives the covert signals with its magnetic sensor. I present technical background, discuss signal generation, data encoding, and signal reception. The proposed covert channel works from a user-level process, without requiring special privileges, and can successfully operate from within an isolated virtual machine (VM).

Review on GPS spoofing‐based time synchronisation attack on power system

Power utilities implement cyber-security defence with a philosophy of defence in-depth. Firewall and air-gapped systems are widely used to harden cybersecurity defence of critical power system infrastructure. However, cyber-attack, such as global positioning system (GPS) spoofing, that can compromise the air-gap system has not been investigated thoroughly. As a geographically dispersed cyber-physical system, the power system relies heavily on the GPS to keep time synchronisation of different parts with high precision. GPS spoofing-based time synchronisation attack (TSA) could induce disorder in time synchronisation, and negatively impact or even disable monitoring and control function of the power system via their operation mechanism. The principles of GPS-based time synchronisation and GPS spoofing-based TSA are introduced. Time synchronisation and operation mechanism of typical monitoring and control systems of the power systems are analysed. Thereafter, the consequences of TSA against these systems are analysed. Various techniques that can be used to defend against TSA are depicted and their performances are analysed.

Force Calculation by Reluctance Method in Triangular Air Gap Magnetic System

Magnetic circuit in MCCB should be reliable as Reliability is the main concern if MCCB used as the protection to the main appliances. Air-gap plays critical role in any magnetic system as increase and decrease in it will cause shift in saturation level. In this paper we are going to see the effect of air-gap variation in case of triangular air-gap. Here, Ansys software is used for magneto static analysis of the magnetic system. Relation between analytic formulation and ansys data is given by variation factor, which is used to establish force in given triangular system by just mathematical formulation. This paper will help in driving force for any triangulate air-gap system and relation between system and simulating software. Formulation of force generation is very important at design point of view as it will help in analyzing required force generation.

Exfiltrating data from an air-gapped system through a screen-camera covert channel

In recent years, many methods of exfiltrating information from air-gapped systems, including electromagnetic, thermal, acoustic and optical covert channels, have been proposed. However, as a typical optical channel, the screen-camera method has rarely been considered; it is less covert because it is visible to humans. In this paper, inspired by the rapid upgrades of cameras and monitors, we propose an air-gapped screen-camera covert channel with decreased perceptibility that is suitable for complex content. Our method exploits the characteristics of the human vision system (HVS) and embeds quick response (QR) codes containing sensitive data in the displayed frames. This slight modification of the frames cannot be sensed by the HVS but can be recorded by the cameras. Then, using certain image processing techniques, we reconstruct the QR codes to some degree and extract the secret data with a certain level of robustness due to the error correction capacity of QR codes. In the scenario to which our method applies, we assume that a program has been installed in the target system and has the authority to modify the frames without affecting the normal operations of valid users. Cameras, such as web cameras, surveillance cameras and smartphone cameras, can be receivers in our method. We illustrate the applicability of our method to frames with complex content using several different cover images. Experiments involving different angles between the screen and the camera were conducted to highlight the feasibility of our method with angles of $ 0^{\circ}, 15^{\circ}$ and $30^{\circ} $.

Russian attackers breach US electricity network

Russian hackers managed to access supposedly air-gapped systems in order to penetrate the control room of an unnamed US power company, according to a report in the Wall Street Journal.

An Approach to Secure Air-gap system from Intentional Radio Transmission

29May 2016 An Approach to Secure Air-gap system from Intentional Radio Transmission Gaurav Neelwarna and S. Magesh M. Tech. Student, Faculty of Engineering and Technology, SRM University, Chennai, India. Assistant Professor, Faculty of Engineering and Technology, SRM University, Chennai, India.

Study on the Optimal Switching Frequency for Maximum Wireless Power Transfer in a Variable Airgap System

This paper presents the optimal switching frequency for maximum wireless power transfer (WPT) used in railway applications that have a variable airgap. Voltage gain is one of key elements judging the system performance, and can be presented as a function of the switching frequency and number of primary winding turns. The optimal switching frequency in the given parameters for WPT has been investigated in detail using a simulation. From the results, the optimal switching frequency obtained for maximum power transfer according to the design variables such as airgap, number of primary windings, mean length turns, and leakage flux, was different from the resonant frequency for maximum efficiency.

AC performance of silicone and glass barriers in clean and polluted atmosphere

The aim of this article consists in the comparative study of silicone rubber and glass insulating barriers performance. The study is carried out under AC voltage in a clean and polluted atmosphere. Their dielectric properties needed to characterize their performance were measured using the Schering bridge. The effect of the grounded electrode's sizes and their isolation in the point–plane air gap system on the optimization of the insulating barrier performance was analyzed. Moreover we present findings of experiments which allow quantifying the effects of the clean or polluted atmosphere, the degree of contamination, the number of polluted faces of the barrier as well as the electrode axis orientation of the rod–plane system on their protection reliability.Finally, this investigation has been supported by laboratory observations of the discharge phenomena in the air gap from inception to full flashover in all cases using a video camera system. The results from this study argue well for the use of silicone insulation as a barrier in non-uniform field electrode systems regardless of the nature of the environment in which it must operate.

Effect of isolation mode and surface condition of an insulating barrier on the performance of a non-uniform field electrode system under positive DC voltage

The aim of this paper is the study of the effect of the isolation and the surface condition of an insulating barrier on the performance of a non-uniform field electrode system. The study is carried out under positive DC voltage. The dielectric properties of the material were measured using the Schering bridge. The effect of the material isolation mode in the point-plane air gap system on the optimisation of its performance was analyzed. Moreover we present findings of experiments which allow quantifying the effects of the clean or polluted atmosphere and the contamination severity level on the electric strength of the air gap system. Finally, this investigation has been supported by laboratory observations of the discharge phenomena in the air gap from inception to full flashover in all cases using a video camera system. The results from this study show that there is a distance limit of the isolation barrier beyond which its performance is optimal. In addition, a limit level of pollution, from which its minimal electric strength is equivalent to that of a conducting barrier, has been detected.

Impact of the earthworm Aporrectodea trapezoides and the arbuscular mycorrhizal fungus Glomus intraradices on 15N uptake by maize from wheat straw

The interactive impacts of an arbuscular mycorrhizal fungus (AMF; Glomus intraradices) and an earthworm species (Aporrectodea trapezoides) on N uptake by maize growing during wheat straw decomposition was studied with a modified up–down two-compartment root containers incorporating an air gap system. Soil was sterilized and root compartments inoculated with AMF inoculum in each treatment. Treatments comprised hyphal compartments (HC) with or without AMF hyphae and with or without earthworms. Wheat straw labeled with 15N was added to the HC. We determined maize yield, 15N content of shoots and roots, concentration of inorganic 15N in soil, percent of 15N transfer, and soil microbial biomass and community composition as indicated by phospholipid fatty acid profiles of HC soil at harvest. Earthworms enhanced 15N mineralization by 47.7 % from wheat straw compared to the control but did not directly increase N mineralization or transfer N from mycorrhizae to plant. AMF hyphae increased shoot and root 15N uptake by 117.9 and 87.4 %, respectively. Interaction between the AMF and earthworms increased shoot and root 15N uptake by 22.0 and 36.2 %, respectively, (compared to hyphae alone) and decreased soil 15N content by 28.9 % (compared to earthworms alone). The AMF hyphae assisted maize in the uptake of 15N mineralized from wheat straw by earthworms. Interactions between earthworms and AMF may help plants to take up N mineralized from crop residues.

Quasistatic and dynamic piezoelectric coefficients of polymer foams and polymer film systems

Piezoelectric properties of polymer electrets consisting of cellular polypropylene (PP) or of porous polytetrafluoroethylene (PTFE) with thicknesses of 50 to 100 /spl mu/m are studied. In addition, bilayer or multilayer structures composed of one of these polymers in solid or voided form plus an additional air layer are investigated. In particular, the quasistatic and the dynamic piezoelectric d/sub 33/ coefficients are determined with electro-mechanical, optical, and acoustic methods. The quasistatic coefficients are of the order of 100 to 350 pC/N for the cellular PP and much lower for the porous PTFE. With increasing frequency up to about 50 kHz the coefficient of cellular PP decreases where it starts to rise toward the resonance at approximately 300 kHz. The bilayer or multilayer structures show considerably higher quasistatic coefficients which reach up to 20,000 pC/N for certain combinations. As for the single-layer systems, a decrease toward higher frequencies is observed. The effect is linear as a function of load pressure at relatively low pressures, ranging up to 100 Pa for some air-gap systems and up to several kPa for the cellular PP.

Comments on “Sound absorption characteristics of air-gap systems in enclosed cavities”

Comments on “Sound absorption characteristics of air-gap systems in enclosed cavities”

Adaptable air gap baffle seal and system

Adaptable air gap baffle seal and system

자속경로 단면적 및 공극변화를 이용한 인던턴스형 초정밀 변위측정 시스템

A variable air-gap type system is widely used for inductive precision position measurement systems. This type transducer has high sensitivity but lacks a linear measurement range due to structural nonlinearity. Furthermore, as measurement range increases, linearity error is also increased. The alternative is a variable overlap-area type system. The sensitivity of this type is determined by the initial air-gap dimension, keeps the original value and does not deteriorate linearity in spite of the variations of the measuring range.