Secure Cloud Data Storage System Using Hybrid Paillier–Blowfish Algorithm

Cloud computing utilizes enormous clusters of serviceable and manageable resources that can be virtually and dynamically reconfigured in order to deliver optimum resource utilization by exploiting the pay-per-use model. However, concerns around security have been an impediment in the extensive adoption of the cloud computing model. In this regard, advancements in cryptography, accelerated by the wide usage of the internet worldwide, has emerged as a key area in addressing some of these security concerns. In this document, a hybrid cryptographic protocol deploying Blowfish and Paillier encryption algorithms has been presented and its strength compared with the existing hybrid Advanced Encryption Standard (AES) and Rivest Shamir Adleman (RSA) techniques. Algorithms for secure data storage protocol in two phases have been presented. The proposed hybrid protocol endeavors to improve the power of cloud storage through a decrease in computation time and cipher-text size. Simulations have been carried out with Oracle Virtual Box and Fog server used on an Ubuntu 16.04 platform. This grouping of asymmetric and homomorphic procedures has demonstrated enhanced security. Compression usage has helped in decreasing the storage space and computation time. Performance analysis in terms of computation overhead and quality of service parameters like loads of parameters with and without attacks, throughput, and stream length for different modes of block cipher mode has been carried out. Security analysis has been carried out by utilizing the Hardening Index as an audit parameter using Lynis 2.7.1. Similarly, for halting the aforementioned approaches and for regulating traffic, firewall protection has been generated in the chosen hybrid algorithms. Finally, enhancements in the performance of the Paillier and Blowfish hybrid scheme with and without compression compared to the existing schemes using RSA and AES procedures have been demonstrated.     

Microstructural Investigation,Raman and Magnetic Studies on Chemically Synthesized Nanocrystalline Ni-Doped Gadolinium Oxide (Gd<Subscript>1.90</Subscript>Ni<Subscript>0.10</Subscript>O<Subscript>3−<Emphasis Type="Italic">δ</Emphasis></Subscript>)

Nanocrystalline Ni-doped gadolinium oxide (Gd_1.90Ni_0.10O_3?δ, GNO) is synthesized by co-precipitation method. The as-prepared sample is annealed in vacuum at 700°C for 6 h. Analyses of the x-ray diffractogram by Rietveld refinement method, transmission electron microscopy and Raman spectroscopy of GNO recorded at room temperature confirmed the pure crystallographic phase and complete substitution of Ni-ions in Gd₂O₃ lattice. Magnetization (M) as a function of temperature (T) and magnetic field (H) is measured by a superconducting quantum interference device magnetometer, which suggests the presence of ferromagnetic/antiferromagnetic phases together with a paramagnetic phase. From the M–T curve it can be shown that the ferromagnetic phase dominates over para-/antiferromagnetic phases in the temperature range of 300–100 K, but from 100 K to 50 K, the antiferromagnetic phase dominates over ferro-/paramagnetic phases. Hysteresis loops recorded at different temperatures indicate the presence of weak ferro-/antiferromagnetism, which dominates in the low field region (～ 4000 Oe), above which magnetization increases linearly. The sharp increase of magnetization in M–T curve observed in the temperature range of 50–5 K confirms the presence of dominating ferromagnetic plus paramagnetic phase over antiferromagnetic part. For the first time a combined formula generated from three-dimensional (3D) spin wave model and Johnston formula is proposed to analyze the coexistence of different magnetic phases in different temperature ranges. Interestingly, the combined formula successfully explains the co-existence of different magnetic phases along with their contribution at different temperatures. The onset of ferromagnetism in Gd_1.90Ni_0.10O_3?δ is explained by oxygen vacancy mediated F-centre exchange (FCE) coupling mechanism.     

Energy transfer and photoluminescent analysis of a novel color-tunable Ba2Y1-xV3O11:xSm3+ nanophosphor for single-phased phosphor-converted white LEDs

Metal nitrates are used to synthesize a series of novel Ba₂Y_1-xV₃O₁₁:xSm³⁺ nanophosphors via urea-assisted solution combustion route. X-ray diffraction (XRD), diffuse reflectance (DR), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were employed to analyse the structure, morphology, photoluminescent behaviour and energy transfer mechanism. Rietveld analysis over Ba₂Y_0.98Sm_0.02V₃O₁₁ showed that Y³⁺ ions can be well-replaced by trivalent samarium ions without resulting any major alteration in the crystal structure of host lattice. Furthermore, the lattice parameters were determined for both the host as well as the doped composition. The Scherrer equation yielded an average particle size of 44?nm, which in turn was further confirmed by TEM micrographs. The optical band-gap of the host (3.92?eV) was calculated from the diffuse reflectance spectra. Moreover, the photoluminescence spectral studies showed that under near ultra-violet (NUV) excitation of 340?nm, our nanophosphor powder exhibits the characteristic emission peaks of trivalent samarium along with the emission of VO₄^3? (501?nm) group. The excitation energy transfer from vanadate group to Sm³⁺ produced a systematic color tunablity in white region itself. The optimum Sm³⁺ concentration for better luminescence was found to be 2?mol%. The critical distance for energy transfer was calculated to be 29.02?Å, which in turn assisted to shortlist the mechanism responsible for luminescence-quenching (dipole-dipole) arising from the over-doping of the activator. The photoluminescence decay curves revealed the decay kinetics of ⁴G_5/2 electronic state. Finally, the calculation of CIE color coordinates from emission spectra in MATLAB program unveiled a somewhat white-light emitter which may find potential applications in phosphor-converted white light emitting diodes (PC-WLED) under near-ultraviolet (NUV) excitation.     

Synthesis of some benzothiazoles by developing a new protocol using urea nitrate as a catalyst and their antimicrobial activities

The present communication demonstrates the development of urea nitrate as an effective and efficient catalyst for the synthesis of some 2-substituted benzothiazoles. Instant progress of reaction at room temperature under solvent-free condition, very high catalytic activity, inexpensive, clean reaction profile, operational simplicity, large-scale synthesis and appreciable yields are the main advantages of this protocol. These synthesized benzothiazoles have been evaluated for their antibacterial and antifungal activities against Gram-positive bacterium (Bacillus subtilis MTCC 121); two Gram-negative bacteria (Escherichia coli MTCC 1652 and Pseudomonas aeruginosa MTCC 741) and two fungi (Candida albicans MTCC 3017 and Saccharomyces cerevisiae MTCC 170). Compound 3n was found the most active against all the tested microbes.     

Enhanced nanocrystalline silicon solar cell with a photonic crystal back-reflector

Nanocrystalline silicon solar cells were enhanced with a photonic crystal back-reflector. Rigorous scattering matrix simulations were used to optimize a photonic crystal back-reflector consisting of a triangular lattice of nano-holes, with a pitch near 800 nm. The photonic crystal back-reflector with a pitch of 800 nm was fabricated on the crystalline silicon substrate by photolithography and reactive-ion etching, and coated with silver and zinc oxide. Nanocrystalline silicon solar cells were grown on the patterned substrates. We observed ～7% enhancement of the absorption and photo-generated current relative to a Ag/ZnO substrate, with an enhancement ratio of 1.5 near the band edge. Significant enhancement occurred in photon absorption at near infrared wavelengths greater than 700 nm, due to diffraction resonances of the incoming light.     

Non-Newtonian blood flow with magnetic nanoparticles in a W-shaped stenosed arterial segment: A numerical study

Flow of blood, infused with magnetic nanoparticles, in a W-shaped stenosed human arterial segment is studied numerically using a realistic non-Newtonian blood rheology model. It is observed that the Newtonian model predicts less time to reach a steady state than the non-Newtonian blood rheology model. An increased drug retention time at the target site with an increase in nanoparticle concentration is predicted. Detailed simulations further reveal that the skin friction coefficient does not increase significantly with the increase in nanoparticle concentration. Hence, it is anticipated from our study that the infusion of drug-carrying nanoparticles in blood flow does not excessively enhance wall shear stress that may lead to arterial wall damage. An overall increase in heat transfer rates and wall shear stress at the stenosed section is seen with an increase in Reynolds number. The present study provides valuable information for designing computer-assisted drug delivery systems.