EmLog:Tamper-Resistant System Logging for Constrained Devices with TEEs

Remote mobile and embedded devices are used to deliver increasingly impactful services, such as medical rehabilitation and assistive technologies. Secure system logging is beneficial in these scenarios to aid audit and forensic investigations particularly if devices bring harm to end-users. Logs should be tamper-resistant in storage, during execution, and when retrieved by a trusted remote verifier. In recent years, Trusted Execution Environments (TEEs) have emerged as the go-to root of trust on constrained devices for isolated execution of sensitive applications. Existing TEE-based logging systems, however, focus largely on protecting server-side logs and offer little protection to constrained source devices. In this paper, we introduce EmLog -- a tamper-resistant logging system for constrained devices using the GlobalPlatform TEE. EmLog provides protection against complex software adversaries and offers several additional security properties over past schemes. The system is evaluated across three log datasets using an off-the-shelf ARM development board running an open-source, GlobalPlatform-compliant TEE. On average, EmLog runs with low run-time memory overhead (1MB heap and stack), 430--625 logs/second throughput, and five-times persistent storage overhead versus unprotected logs.Comment: Accepted at the 11th IFIP International Conference on Information Security Theory and Practice (WISTP '17

Influence of recycled basalt-aramid fibres integration on the mechanical and thermal properties of brake friction composites

In the brake friction composites(BFCs), fibres take part in significant attention as reinforcement in governing mechanical and thermal-mechanical properties. The current investigation aims to develop hybrid brake friction composites using recycled basalt- aramid fibre integration and to characterise for its mechanical and thermal properties. The experiments related to thermal (heat swell, loss of ignition and thermal conductivity) and mechanical (tensile, compression, flexural and impact) properties were conducted as per industrial standards. From the experimental investigations, it was concluded that fibre inclusion in the BFCs enhanced the mechanical and thermal properties considerably. Further, with the aid of scanning electron microscope (SEM), fracture interfaces of the tested friction composites were analyzed for various characteristics like pullout, void, fibre-matrix bonding etc

Characterization of raw and alkali treated new natural cellulosic fibers from Tridax procumbens

The aim of this study is to investigate natural cellulosic fibers extracted from Tridax procumbens plants. The obtained fibers were alkali treated for their effective usage as reinforcement in composites. The physical, chemical, crystallinity, thermal, wettability and surface characteristics were analyzed for raw, and alkali treated Tridax procumbens fibers (TPFs). The test results conclude that there was an increase in cellulose content with a reduction in hemicellulose, lignin, and wax upon alkali treatment. This enhanced the thermal stability, tensile strength, crystallinity, and surface roughness characteristics. The contact angle was also lesser for treated TPFs which prove its better wettability with the liquid phase. The Weibull distribution analysis was adopted for the analysis of the fiber diameter and tensile properties. Thus the considerable improvement in the properties of alkali treated TPFs would be worth for developing high-performance polymer composites

Characterization of Alkali-Treated and Untreated Natural Fibers from the Stem of Parthenium Hysterophorus

In the current study, deals with the characterization of Parthenium hysterophorus fibers (PHF) extracted from its stem by manual retting process. Then, extracted fibers were alkali-treated, and its characteristics were compared with untreated one. The various behaviors of the alkali-treated and untreated PHF was studied using physical-chemical analysis, Fourier-transform infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis, Tensile test, and Scanning Electron Microscopy. Results showed that alkali-treated PHF showed an increase in cellulose content by 8.9% than untreated PHF while the char residue was 38.5%. It also showed a better crystalline index, surface characteristics, and good tensile strength

Characterization of Silane-Treated and Untreated Natural Fibers from Stem of Leucas Aspera

In recent years, natural fiber and its composites have attracted researchers due to environmental awareness. It is essential to identify new cellulose fibers for the potential polymer reinforcement. The current study deals with the investigation of natural cellulosic fibers extracted from the stem of Leucas aspera plants. The obtained fibers were treated with silane for effective use in composite applications. The physical, chemical, crystallinity, thermal stability, and morphological characteristics were analyzed for both untreated and silane-treated Leucas aspera fibers using chemical analysis, X-Ray diffraction test, fourier transform infrared spectroscopy, thermogravimetric analysis, and SEM images. The results showed that silane treatment removed excess lignin, wax and hemicellulose contents from Leucas aspera fibers and helped to increase its bonding characteristics with the matrix in composite applications leading to enhanced results compared to the untreated samples. There was a 2.1 times increase in crystalline index and better thermal stability with a char residue of 39%. To prove the applications' suitability, epoxy composites and friction composites in the form of brake pads were developed and analyzed for their mechanical performance as per ASTM and standard industrial practice. Increase in ultimate tensile strength was 56 MPa for silane-treated Leucas aspera fiber based epoxy composites while it was 43 MPa compared to its untreated samples. In brake pads, hardness was 93 for silane-treated LA fiber-based brake pads and 87 for the untreated

Characterization of Novel Natural Fiber from Saccharum Bengalense Grass (Sarkanda)

The exploration of novel natural fibers can contribute to expand their use in possible eco-friendly applications. In the current work, the physicochemical, thermal, tensile and morphological characteristics were tested for the fibers extracted from the stem of Saccharum Bengalense grass (SB). The results showed that fiber possesses good chemical constituents, namely, α- cellulose (53.45%), hemicellulose (31.45%) with lower lignin (11.7%) as confirmed from chemical analysis, its presence confirmed from Fourier Transform Infrared Spectroscopy (FTIR). Due to the presence of considerable chemical constituents, SB fibers showed good crystallinity index and tensile strength as confirmed from X-Ray diffraction analysis (XRD) and tensile test. Thermal stability was found using Thermogravimetric analysis (TGA), it revealed the SB fibers showed maximum degradation at 336°C and the char residue was 16.4%. Scanning Electron Microscopy (SEM) was used to study the morphological characteristics. Thus, SB fibers could be used as reinforcement in natural fiber-based polymer composites. This fiber utilization in composites may be suggested in potential applications like roofing sheets, bricks, door panels, furniture panels, interior paneling, storage tanks, pipelines, etc

Extraction and Characterization of Natural Fiber from Stem of Cardiospermum Halicababum

The current study deals with the investigation on the properties of lignocellulose fiber from the stem of Cardiospermum Halicababum. The Cardiospermum Halicababum fibers (CHF) were extracted from its stem by manual retting process. The retted fibers were analyzed for various physical, chemical, crystalline, thermal stability, tensile and morphological properties as per standard procedure. From the chemical investigation, it was found that the CHF has cellulose (59.82%), hemicellulose (16.75%), lignin (9.3%) and wax (1.3%). The CHF possessed a crystallinity index of 32.21%, with thermal stability up to 336°C. The average ultimate tensile strength of CHF was 20.7 ± 1.0 MPa. Morphological characteristics showed lesser lacuna space in between the cell walls thereby preventing the reduction in strength properties

Characterization of Natural Fibers from Cortaderia Selloana Grass (Pampas) as Reinforcement Material for the Production of the Composites

Due to environmental problems by the use of synthetic fibers in composite materials, researchers are more concerned with searching for eco-friendly materials. Consequently, the use of reinforcing fibers of natural origin is the best option that promotes the obtaining of materials that do not harm the environment. This paper presents characterization of Cortaderia selloana grass (Pampas) fibers by physical-chemical analysis, FTIR, XRD, thermogravimetric analysis, single fiber tensile test and SEM analysis. Diameter (372.6 µm), density (1261 kg/m3), cellulose content (53.7 wt.%), crystallinity index (22%), tensile strength (20 ± 1.0 MPa), Young’s modulus (8.88 GPa), and thermal stability (320°C) properties were identified in the Cortaderia selloana grass (Pampas) fibers. Overall properties of these fibers showed that it could be an alternative source as reinforcement material for the manufacture of composite materials

Extraction and characterization of natural fiber from Eleusine indica grass as reinforcement of sustainable fiber reinforced polymer composites

In the present scenario, the searching for novel plant fibers able to be used as reinforcement of polymer composites is highly appreciable. This study deals with extraction and characterization of Eleusine indica grass fibers extracted from its stem by manual retting process. From this study, it was found that the Eleusine indica has higher cellulose of 61.3 wt% content, density of 1143 kg/m3, average tensile strength and Young’s modulus equal to 22 MPa and 10.75 GPa, respectively. From the XRD studies, it was noted that the Crystallinity Index (CI) of Eleusine indica was 45%. The surface morphology of Eleusine indica grass was examined using a Scanning Electron Microscope (SEM) and Chemical functional group were confirmed by Fourier transform infrared spectroscopy (FT-IR). The thermal stability of EIF was evaluated using TG and DTG curves from Thermogravimetric (TG) analysis. The characterization results confirmed that Eleusine indica grass could be used for the production of sustainable fiber-reinforced polymer composites

Extraction and characterization of vetiver grass (Chrysopogon zizanioides) and kenaf fiber (Hibiscus cannabinus) as reinforcement materials for epoxy based composite structures

The study deals with the mechanical characterization of vetiver grass fiber and kenaf fiber reinforced epoxy-based hybrid composites. Five types of composite laminates were developed through the hand lay-up process by varying the percentage of vetiver grass and kenaf fibers. The tensile, flexural, compression and impact tests were conducted as per ASTM. The fractured surfaces of the tested specimens were studied using a scanning electron microscope. From the results, it was shown that properties of epoxy composites were improved by hybridization with vetiver grass and kenaf fibers. The improved mechanical properties of fiber-reinforced composites were noticed in increment of percentage composition of kenaf fibers