A Multi-view Context-aware Approach to Android Malware Detection and Malicious Code Localization

Existing Android malware detection approaches use a variety of features such as security sensitive APIs, system calls, control-flow structures and information flows in conjunction with Machine Learning classifiers to achieve accurate detection. Each of these feature sets provides a unique semantic perspective (or view) of apps' behaviours with inherent strengths and limitations. Meaning, some views are more amenable to detect certain attacks but may not be suitable to characterise several other attacks. Most of the existing malware detection approaches use only one (or a selected few) of the aforementioned feature sets which prevent them from detecting a vast majority of attacks. Addressing this limitation, we propose MKLDroid, a unified framework that systematically integrates multiple views of apps for performing comprehensive malware detection and malicious code localisation. The rationale is that, while a malware app can disguise itself in some views, disguising in every view while maintaining malicious intent will be much harder. MKLDroid uses a graph kernel to capture structural and contextual information from apps' dependency graphs and identify malice code patterns in each view. Subsequently, it employs Multiple Kernel Learning (MKL) to find a weighted combination of the views which yields the best detection accuracy. Besides multi-view learning, MKLDroid's unique and salient trait is its ability to locate fine-grained malice code portions in dependency graphs (e.g., methods/classes). Through our large-scale experiments on several datasets (incl. wild apps), we demonstrate that MKLDroid outperforms three state-of-the-art techniques consistently, in terms of accuracy while maintaining comparable efficiency. In our malicious code localisation experiments on a dataset of repackaged malware, MKLDroid was able to identify all the malice classes with 94% average recall

MRI changes in psoriatic dactylitisextent of pathology, relationship to tenderness and correlation with clinical indices

Objectives. To quantify the extent of inflammation in psoriatic dactylitis and to examine the relationship between clinical and magnetic resonance imaging (MRI) data in both tender and non-tender dactylitis. Methods. Seventeen patients with psoriatic dactylitis underwent clinical assessment for 6 months after change of treatment, usually to methotrexate. Measures of dactylitis included the Leeds Dactylitis Index, the assessment tool used in the Infliximab in Psoriatic Arthritis Clinical Trial (IMPACT), a simple count of tender dactlylitic digits and a count of all dactylitic digits, both tender and non-tender. MRI scans of the affected hand or foot were performed before and after treatment using a 1.5T Siemens scanner pre- and post-contrast. Results. All patients improved clinically, as did their respective dactylitis scores and MRI images. The findings on MRI in both dactylitic and non-dactylitic digits were profound and widespread. The difference between tender and non-tender dactylitis was quantitative rather than qualitative. Synovitis and soft-tissue oedema were the most frequent abnormalities being present in 69 of tender dactylitic digits but bone oedema and flexor tenosynovitis were also frequently seen. Soft-tissue oedema was circumferential and enhancing and not limited to association with the flexor or extensor tendons. None of the clinical indices of dactylitis showed a close relationship to the extent of MRI abnormalities. Conclusions. MRI images demonstrate widespread abnormalities in digits of people with psoriatic arthritis. Tender dactylitic digits have more abnormalities than other digits but the relationship between clinical and MRI scores is not strong

Real-Time High Resolution Integrated Optical Micro-Spectrometer

A real-time integrated planar single-mode waveguide grating micro-spectrometer with high resolution of 0.5 nm in 120 nm wide range of visible spectrum, from 525 nm to 645 nm is demonstrated. A CMOS sensor is used for capturing the output image of micro-spectrometer. A f = 1cm lens is used to focus the diffracted monochromatic light onto the CMOS sensor. An algorithm is developed using simple polynomial equation which uses two known reference wavelengths to convert x-pixel numbers of the CMOS sensor to wavelength spectrum. The output of micro-spectrometer in this design has comparatively less noise than usual spectrometric measurements. This design uses built-in matlab functions such as \u27findpeaks\u27 to find the input laser peaks and the central pixel numbers for that peaks and \u27polyfit\u27 to find the coefficients essential for the calibration of wavelength spectrum

Dense Periodical Patterns In Photonic Devices: Technology For Fabrication And Device Performance

For the fabrication, focused ion beam parameters are investigated to successfully fabricate dense periodical patterns, such as gratings, on hard transition metal nitride such as zirconium nitride. Transition metal nitrides such as titanium nitride and zirconium nitride have recently been studied as alternative materials for plasmonic devices because of its plasmonic resonance in the visible and near-infrared ranges, material strength, CMOS compatibility and optical properties resembling gold. Coupling of light on the surface of these materials using sub-micrometer gratings gives additional capabilities for wider applications. Here we report the fabrication of gratings on the surface of zirconium nitride using gallium ion 30keV dual beam focused ion beam. Scanning electron microscope imaging and atomic force microscope profiling is used to characterize the fabricated gratings. Appropriate values for FIB parameters such as ion beam current, magnification, dwell time and milling rate are found for successful milling of dense patterns on zirconium nitride. For the device performance, a real-time image-processing algorithm is developed to enhance the sensitivity of an optical miniature spectrometer. The novel approach in this design is the use of real-time image-processing algorithm to average the image intensity along the arc shaped images registered by the monochromatic inputs on the CMOS image sensor. This approach helps to collect light from the entire arc and thus enhances the sensitivity of the device. The algorithm is developed using SiTiO2 planar waveguide. The accuracy of the mapping from x-pixel number scale of the CMOS image sensor to the wavelength spectra of the miniature spectrometer is demonstrated by measuring the spectrum of a known LED source using a conventional desktop spectrometer and comparing it with the spectrum measured by the miniature spectrometer. The sensitivity of miniature spectrometer is demonstrated using two methods. In the first method, the input laser power is attenuated to 0.1 nW and the spectra is measured using the miniature spectrometer. Even at low input power of 0.1nW, the spectrum of monochromatic inputs is observed well above the noise level. Second method is by quantitative analysis, which measures the absorption of CdSeS/ZnS quantum dots drop casted between the gratings of Ta2O5 planar single-mode waveguide. The expected guided mode attenuation introduced by monolayer of quantum dots is found to be approximately 11 times above the highest noise level from the absorption measurements. Thus, the miniature spectrometer is capable of detecting the signal from the noise level even with the absorption introduced by monolayer of quantum dots

Fabrication of semiconductor nanowire multifunctional devices

Portable multi-functional devices can play a major role in the new age society embracing internet-of-things (IoT). Being able to perform primary functions such as sensing and secondary functions such as storing information is quite critical when out of connectivity. However, such bespoke devices are almost unheard of as it is very difficult to fabricate it due to several factors such as device architecture, dimension, scalability, and parasitic effects. This work describes the fabrication and characterization of a multi-functional device that acts an ultra-sensitive pressure sensor but is also capable of storing that information for a prolonged period. Both sensitivity and charge storage ability are attributed to the inclusion of one-dimensional (1-D) nanostructures. The alternating crystal phases in the as-grown gold (Au) catalyzed GaAs and self-induced AlGaAs/GaAs nanowires (NWs) were used in our case. This thesis discusses the fabrication, growth, characterization, integration and electrical testing involved to produce the multi-functional device. Bespoke nanowires were grown on a template prepared using a combination of nanosphere (NSL) and nanoimprint lithography (NIL) which provided a reproducible large-area periodic array of growth site at a relatively low cost. The inclusion of these NWs in the polymer helps enhance the relative permittivity of the host polymer by a factor of 40 making it an almost-perfect dielectric for a capacitive pressure sensor. NWs also acted as charge storage nodes allowing to extend the functionality. The technique consists of creating nanoholes in silicon dioxide (SiO2) to expose the silicon Si (111) beneath where self-induced NWs can nucleate, while nanodots deposited onto the Si (111) surface serve as catalyst seeds. For Au-catalysed NWs, a monolayer of self-assembled polystyrene nanospheres (PNS 300 nm) was created on a 2 inch Si wafer by spin coating and later etched for a short time before a very thin Au-catalyst layer was deposited. In turn, for self-induced, PNS monolayer was created onto a SiO2-Si substrate. A longer etch was required to reduce PNS diameter significantly to leave relatively larger spacing where chromium is blanket deposited. PNS were lifted off by sonicating the samples in toluene produce the periodic arrays of nanodots and nanoholes, respectively. The underlying SiO2 was etched further through the nanoholes to uncover the Si below. 200 nm holes and 30-70 nm dots were demonstrated through the bespoke methods. The patterned substrates served as master templates, subsequently copied using polydimethylsiloxane (PDMS) to produce a flexible stamp for nanoimprint lithography. A bi-layer resist lift off process was developed to print the replicated nanodots or nanoholes on large-area substrates onto which GaAs NWs were subsequently grown. GaAs NWs were extracted and mixed in PMMA to produce a composite dielectric which was sandwiched between electrodes to act as a capacitor. An order of magnitude increase in relative permittivity (ϵr) is observed after the addition of the NWs allowing a high signal to noise ratio output on the application of pressure. This is due to the addition of higher permittivity nano-filler in the matrix. Furthermore, it was demonstrated that encapsulated high aspect ratio NWs in a host (polymer in this case) can be integrated in devices to improve existing functionality. Devices were successfully fabricated for pressure sensing and memory using the above described low-cost high-volume process with high sensitivity and large memory window, respectively. This demonstration is one of the first steps in enabling low cost electronics without compromising on performance which is imperative for IoT

Measurement of particle interaction properties for the incorporation into Discrete Element Methods

Includes bibliographical references (leaves 213-215).The principle aim of this research project is to measure parameters which are pertinent for numerical simulations in discontinuous media. One such numerical tool, the Discrete Element Method (DEM), is a promising technique for predicting the dynamics of charge motion with in a mill. Particle interactions in DEM are calculated by contact force and force displacement laws at each particle contact. These contact events are characterized by parameters that are often fitted or estimated due to the lack of accurate experimental measurements. The aim of this project is to experimentally measure the necessary interaction properties required for the DEM analysis and to test the DEM models against the measured experimental results. An in-flight binary collisions drop tester is constructed to measure the material interaction properties of two spheres. The collision event is captured photographically and pre- and post- relative velocities are measured. The binary collisions of the particles are carefully controlled by relay timing circuits and they are captured on digitized images using a SLR digital camera. The particles are illuminated using digital strobes controlled by a signal generator. The heights of the colliding particles are adjusted to vary the drop velocities prior to collision. The measured relative velocities arc applied in rigid body theory of binary impact to extract the required material interaction properties. The parameters measured from the binary collision include coefficients of tangential and normal restitution and friction. The analysis presented here draws on the work of Maw et al and Foerster et al, which is an extension of the Hertz theory of impact to the oblique impact of the elastic bodies with circular contacts. Initial numerical simulations using the viscous damping model is performed in Particle Flow Code (PFC) and a comparison between experimental and numerical results presented