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search.filters.applied.f.access: openAccess × End date: 2021 × End date: 2019 × Type: Article × Version: acceptedVersion ×

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    On wireless channel parameters for key generation in industrial environments
    (New York, NY : IEEE, 2017) Kreiser, Dan; Dyka, Zoya; Kornemann, Stephan; Wittke, Christian; Kabin, Ievgen; Stecklina, Oliver; Langendoerfer, Peter
    The advent of industry 4.0 with its idea of individualized mass production will significantly increase the demand for more flexibility on the production floor. Wireless communication provides this type of flexibility but puts the automation system at risk as potential attackers now can eavesdrop or even manipulate the messages exchanged even without getting access to the premises of the victim. Cryptographic means can prevent such attacks if applied properly. One of their core components is the distribution of keys. The generation of keys from channel parameters seems to be a promising approach in comparison to classical approaches based on public key cryptography as it avoids computing intense operations for exchanging keys. In this paper we investigated key generation approaches using channel parameters recorded in a real industrial environment. Our key results are that the key generation may take unpredictable long and that the resulting keys are of low quality with respect to the test for randomness we applied.
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    Effect of Ge-doping on the short-wave, mid- and far-infrared intersubband transitions in GaN/AlGaN heterostructures
    (Bristol : IOP, 2017) Lim, Carolin B.; Ajay, Akhil; Lähnemann, Jonas; Bougerol, Catherine; Monroy, Eva
    This paper assesses the effects of Ge-doping on the structural and optical (band-to-band and intersubband (ISB)) properties of GaN/AlGaN multi-quantum wells (QWs) designed to display ISB absorption in the short-wave, mid- and far-infrared ranges (SWIR, MIR, and FIR, respectively). The standard c-plane crystallographic orientation is considered for wells absorbing in the SWIR and MIR spectral regions, whereas the FIR structures are grown along the nonpolar m-axis. In all cases, we compare the characteristics of Ge-doped and Si-doped samples with the same design and various doping levels. The use of Ge appears to improve the mosaicity of the highly lattice-mismatched GaN/AlN heterostructures. However, when reducing the lattice mismatch, the mosaicity is rather determined by the substrate and does not show any dependence on the dopant nature or concentration. From the optical point of view, by increasing the dopant density, we observe a blueshift of the photoluminescence in polar samples due to the screening of the internal electric field by free carriers. In the ISB absorption, on the other hand, there is a systematic improvement of the linewidth when using Ge as a dopant for high doping levels, whatever the spectral region under consideration (i.e. different QW size, barrier composition and crystallographic orientation).