Smart homes are a special use-case of the IoT paradigm, which is becoming more and more important in our lives. Although sensors, devices and applications make our daily lives easier, they often collect our sensitive data, which may lead to security problems (e.g., hacked devices, botnets, etc.). In several cases, the appropriate security mechanisms are missing within the devices. Therefore, security measures have become a central topic in the field of IoT. The most essential requirements are secure user–device authentication and confidentiality of transferred sensitive data. Passwords are the most widely used factors in various areas, such as user authentication, key establishment, and also secret sharing. Password-based protocols that are resistant to typical threats, such as offline dictionary, man-in-the-middle and phishing attacks, generate new session keys. The major aim of these solutions is to guarantee high-level security, even if a user applies a single low-entropy human memorable password for all their accounts. We introduce a threshold and password-based, distributed, mutual authenticated key agreement with key confirmation protocol for a smart home environment. The proposed protocol is a scalable and robust scheme, which forces the adversary to corrupt \(l-1\) smart home devices, where l is the threshold, in order to perform an offline dictionary attack. The protocol is designed to achieve password-only setting, and end-to-end security if the chosen IoT devices are also authenticated besides the user. We also provide a security analysis of the protocol in AVISPA. We apply the on-the-fly model checker and the constraint-logic-based attack searcher to perform protocol verification for bounded numbers of sessions. We show that the proposed protocol provides session key secrecy and mutual authentication of the user and the device manager. Since efficiency is a crucial aspect, we implemented our protocol to measure the computation and communication costs and demonstrate that our solution is appropriate and eligible for smart homes.
This paper compares the molecular structure and rheological properties of a commercial poly(ethylene terephthalate) (PET) after reactive processing with different concentrations of either pyromellitic dianhydride (PMDA) or a multifunctional epoxide (Joncryl®ADR-4368) as a chain extender. By size exclusion chromatography with triple detection, an increase of molar mass, a broadening of molar mass distribution, and the generation of long-chain branched molecules were found for both chain extenders. While gel-free materials were obtained with PMDA, the processing with Joncryl leads to the formation of gels. The effect of branching, indicated by the Mark–Houwink exponent, is more pronounced for materials with Joncryl compared to PMDA and points to a more compact branching structure of the PET/Joncryl molecules. Rheological measurements in shear and elongation support the analysis from SEC and reveal a complex tree-like branching structure for both chain extenders. In addition, the role of the two modifiers with respect to processing was assessed. 相似文献
Scientometrics - Consolidation of the scientific activity in Latin American research centers has been a matter of serious concern in recent years. In the present study we use a data set of the WoS... 相似文献
One of the most impressive features of moving animal groups is their ability to perform sudden coherent changes in travel direction. While this collective decision can be a response to an external alarm cue, directional switching can also emerge from the intrinsic fluctuations in individual behaviour. However, the cause and the mechanism by which such collective changes of direction occur are not fully understood yet. Here, we present an experimental study of spontaneous collective turns in natural flocks of starlings. We employ a recently developed tracking algorithm to reconstruct three-dimensional trajectories of each individual bird in the flock for the whole duration of a turning event. Our approach enables us to analyse changes in the individual behaviour of every group member and reveal the emergent dynamics of turning. We show that spontaneous turns start from individuals located at the elongated tips of the flocks, and then propagate through the group. We find that birds on the tips deviate from the mean direction of motion much more frequently than other individuals, indicating that persistent localized fluctuations are the crucial ingredient for triggering a collective directional change. Finally, we quantitatively verify that birds follow equal-radius paths during turning, the effects of which are a change of the flock''s orientation and a redistribution of individual locations in the group. 相似文献
The critical shear velocity for resuspension of micrometer size particles from rough surfaces was studied. The random variation of surface roughness was accounted for. The recently developed Monte Carlo simulations accounted for the statistical variations of physical parameters that control the particle resuspension process. A sensitivity analysis showed that the surface roughness and its random variation was the key factor affecting the particle resuspension from rough surfaces. The theory of probabilistic transformation was used and an analytical expression for evaluating the resuspension fraction of particles of different sizes from rough surfaces versus the shear velocity was developed. The resuspension fractions as predicted by the analytical model were evaluated for several particles sizes for a range of turbulent flow shear velocities. The resulting resuspension fractions were compared with those obtained from the Monte Carlo simulations as well as the available experimental data. It was found that the predictions of the new analytical equation were in good agreement with the Monte Carlo simulation results and the experimental data, especially for smaller size particles. This new analytical expression could be used as a simple empirical equation for estimating flow-induced resuspension of particles from rough surfaces. 相似文献
Metallurgical and Materials Transactions B - The reaction between SiO(g) and CO(g) is a relevant intermediate reaction in the silicon production process. One of the products generated from this gas... 相似文献