D. K. Shukla

Beware, Your Hands Reveal Your Secrets!

Research on attacks which exploit video-based side-channels to decode text typed on a smartphone has traditionally assumed that the adversary is able to leverage some information from the screen display (say, a reflection of the screen or a low resolution video of the content typed on the screen). This paper introduces a new breed of side-channel attack on the PIN entry process on a smartphone which entirely relies on the spatio-temporal dynamics of the hands during typing to decode the typed text. Implemented on a dataset of 200 videos of the PIN entry process on an HTC One phone, we show, that the attack breaks an average of over 50% of the PINs on the first attempt and an average of over 85% of the PINs in ten attempts. Because the attack can be conducted in such a way not to raise suspicion (i.e., since the adversary does not have to direct the camera at the screen), we believe that it is very likely to be adopted by adversaries who seek to stealthily steal sensitive private information. As users conduct more and more of their computing transactions on mobile devices in the open, the paper calls for the community to take a closer look at the risks posed by the now ubiquitous camera-enabled devices.

Structural, dielectric, and magnetic properties of La0.8Bi0.2Fe1−xMnxO3 (0.0≤x≤0.4) multiferroics

Polycrystalline multiferroic La0.8Bi0.2Fe1−xMnxO3 (0.0≤x≤0.4) samples were synthesized by the conventional solid state reaction method. Reitveld refinement of the x-ray diffraction patterns confirms the single phase character of all the compositions with orthorhombic structure having space group Pnma (No. 62). Dielectric properties of the samples at temperatures 200–475 K and frequencies 500 kHz–1 MHz authenticate the stabilization of ferroelectric phase with Mn substitution. Dielectric responses of these multiferroics have been analyzed carefully, in the light of “universal dielectric response” model. While cooling from room temperature to 20 K, systematic shifts in magnetization hysteresis loops indicate the presence of exchange bias (EB) phenomenon in the system. Magnetic behavior of these samples has been briefly discussed on the basis of “EB” model for granular systems. Temperature and magnetic field dependent magnetization data demonstrate enhanced magnetization due to the Mn substitution. Magnetocapacitance measurement reveals the magnetoelectric coupling for wide range of temperature (180–280 K) and decrease in dielectric loss at high magnetic field (3 T).Polycrystalline multiferroic La0.8Bi0.2Fe1−xMnxO3 (0.0≤x≤0.4) samples were synthesized by the conventional solid state reaction method. Reitveld refinement of the x-ray diffraction patterns confirms the single phase character of all the compositions with orthorhombic structure having space group Pnma (No. 62). Dielectric properties of the samples at temperatures 200–475 K and frequencies 500 kHz–1 MHz authenticate the stabilization of ferroelectric phase with Mn substitution. Dielectric responses of these multiferroics have been analyzed carefully, in the light of “universal dielectric response” model. While cooling from room temperature to 20 K, systematic shifts in magnetization hysteresis loops indicate the presence of exchange bias (EB) phenomenon in the system. Magnetic behavior of these samples has been briefly discussed on the basis of “EB” model for granular systems. Temperature and magnetic field dependent magnetization data demonstrate enhanced magnetization due to the Mn substitution. Magnetoca...

Structural, magnetic and x-ray absorption studies of NdCo1−xNixO3 (0 ≤ x ≤ 0.5)

We have systematically investigated the effect of Ni substitution on the structural and magnetic properties of NdCoO3. Single phase nature and orthorhombic Pbnm structure is confirmed by the Reitveld refinement of X-ray diffraction data in all samples. X-ray absorption near edge spectroscopy of Co and Ni K-edges reveals the presence of trivalent state of Ni and Co ions in all samples. Composition dependent crossover from canted antiferromagnetic (AFM) (for x < 0.3) to spin glass behavior (for x ≥ 0.3) is observed in magnetic measurements. Low temperature ferromagnetic (FM) component in doped samples is attributed to the stabilization of Co+3 ions in intermediate-spin (IS) state t52ge1g with S = 1 The FM and AFM are observed to coexist as confirmed by M-H hysteresis. Nd sublattice seems to inhibit the magnetic contribution from Co ions, and we ruled out the possibility of charge disproportion induced by Ni substitution leading to FM interactions in these systems as proposed in different reports.

Toward Robotic Robbery on the Touch Screen

Despite the tremendous amount of research fronting the use of touch gestures as a mechanism of continuous authentication on smart phones, very little research has been conducted to evaluate how these systems could behave if attacked by sophisticated adversaries. In this article, we present two Lego-driven robotic attacks on touch-based authentication: a population statistics--driven attack and a user-tailored attack. The population statistics--driven attack is based on patterns gleaned from a large population of users, whereas the user-tailored attack is launched based on samples stolen from the victim. Both attacks are launched by a Lego robot that is trained on how to swipe on the touch screen. Using seven verification algorithms and a large dataset of users, we show that the attacks cause the system’s mean false acceptance rate (FAR) to increase by up to fivefold relative to the mean FAR seen under the standard zero-effort impostor attack. The article demonstrates the threat that robots pose to touch-based authentication and provides compelling evidence as to why the zero-effort attack should cease to be used as the benchmark for touch-based authentication systems.

Electronic structure and electrical transport properties of LaCo1−xNixO3 (0 ≤ x ≤0.5)

The structural analysis of LaCo1−xNixO3 (0 ≤ x ≤ 0.5) samples assures single phase rhombohedral structure with space-group R3¯c. Electronic structure of these samples has been studied by x-ray absorption near edge spectroscopy (XANES) at K-edge of O, Ni, Co and M5,4 edge of La. These studies confirm the trivalent state of Co/Ni and La in all the compositions. Upon substitution of the Ni at the Co site in LaCoO3, the O K-edge spectra show a feature about 1.2 eV lower than that of LaCoO3. This feature keeps on growing as the concentration of the Ni is increasing. This is consistent with our resistivity data which shows drastic decrease in resistivity with the Ni substitution. The resistivity data have been analyzed using Arrhenius and Efros-Shklovskis type variable range hopping models in different temperature ranges. The activation energy decreases and localization length increases systematically with increase in the Ni concentration. Observed features have been explained on the basis of change in charge-...

Ferroelectric and dielectric properties of Mn doped BiFeO3 bulk ceramics

The structural, dielectric and ferroelectric properties of BiFeO3 and BiMnxFe1-xO3 with x = 0.03 samples synthesized by the conventional solid state reaction method has been studied. The XRD pattern clearly shows the suppression of impurity phases with the substitution of Mn at Fe - site. Dielectric properties of the samples in frequency range 4 Hz - 1 MHz has been measured at room temperature. A strong dispersion was observed in the dielectric constant at low frequencies due to Maxwell-Wagner type of interfacial polarization. At higher frequencies, dielectric constant shows frequency independent behavior indicating an intrinsic dielectric response. The BiMn0.03Fe0.97O3 sample exhibit loosy and unsaturated ferroelectric loop at room temperature due to the presence of oxygen vacancies.The structural, dielectric and ferroelectric properties of BiFeO3 and BiMnxFe1-xO3 with x = 0.03 samples synthesized by the conventional solid state reaction method has been studied. The XRD pattern clearly shows the suppression of impurity phases with the substitution of Mn at Fe - site. Dielectric properties of the samples in frequency range 4 Hz - 1 MHz has been measured at room temperature. A strong dispersion was observed in the dielectric constant at low frequencies due to Maxwell-Wagner type of interfacial polarization. At higher frequencies, dielectric constant shows frequency independent behavior indicating an intrinsic dielectric response. The BiMn0.03Fe0.97O3 sample exhibit loosy and unsaturated ferroelectric loop at room temperature due to the presence of oxygen vacancies.

Structural and Magnetic Characterizations of 200 MeV Ag15+ Irradiated BixCo2-xMnO4 Thin Films

The effect of swift heavy ion (SHI) irradiation on the structural and magnetic properties of thin films of Bi-substituted Co2MnO4 prepared by Pulsed Laser Deposition (PLD) is presented. XRD analysis reveals that the BixCo2-x MnO4 (x = 0.0, 0.1 & 0.3) films grown on amorphous quartz, and crystalline LaAlO3 (LAO) exhibited single phase cubic spinel structure with low strain before and after the irradiation at 200 MeV Ag15+ ions at three fluence values 1 × 1011, 5 × 1011 and 1 × 1012 ions/cm2. DC magnetization hysteresis loop study of the films revealed a ferrimagnetic ordering below the transition temperature ~ 185 K and the saturation magnetization was increased by the irradiation at optimal fluence value 51011 ions/cm2. X-ray Magnetic Circular Dichroism (XMCD) studies showed the antiparallel alignments of Co and Mn magnetic moments.

Raman Spectroscopic Studies of Co‐based Spinel Multiferroic Thin Films

Single phase Co‐based spinel multiferroic oxide (BixCo2−xMnO4 x = 0,0.1,0.2&0.3) thin films were synthesized using Pulsed Laser Deposition (PLD) technique. Structural characterizations of thin film samples have been performed using x‐ray diffraction (XRD). Raman spectroscopic data exhibits the doping induced sharp features in characteristic Raman modes and signature of strong electron‐phonon coupling, revealing magnetoelectric multiferroic property of the thin films prepared.