Using trusted execution environment in two-factor authentication: Comparing approaches

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Influence of interpolation scheme on the accuracy of overset method for computing rudder-propeller interaction

The overset method and associated interpolation schemes are usually thoroughly verified only on synthetic or academic test cases for which conclusions might not directly translate to real engineering problems. In the present work, an overset grid method is used to simulate a rudder-propeller flow, for which a comprehensive verification and validation study is performed. Three overset-related interpolation schemes (first order inverse distance, second order nearest cell gradient and third order least squares) are tested to quantify and qualify numerical errors on integral quantities, mass imbalance, flow features and rudder pressure distributions. The performance overhead is also measured to help make accuracy versus performance balance decisions. Rigorous solution verification is performed to estimate time and space Discretization, iterative and statistical uncertainties. Validation of the propeller-rudder flow against experimental data is also done. The results show that, while the choice of interpolation scheme has minimal impact on time-averaged integral quantities (like propeller and rudder forces), they do influence the smoothness of the time signals, with the first order scheme resulting in large intensity high-frequency temporal oscillations. Lower order interpolation methods also produce more interpolation artifacts in fringe cells, which are then convected downstream. Mass imbalance is also affected by the interpolation scheme, with higher order schemes such as the third order least squares approach resulting in an order of magnitude lower flux errors. The limitations of first order schemes do not, however, result in significant lower computational overhead, with the second order nearest cell gradient being even cheaper than the inverse distance scheme in the tested implementation. Lastly, validation shows promising results with rudder forces within 10% of the experiments

The Root Canary: Monitoring and Measuring the DNSSEC Root Key Rollover

The Domain Name System (DNS) is part of the core of the Internet. Over the past decade, much-needed security features were added to this protocol, with the introduction of the DNS Security Extensions. DNSSEC adds authenticity and integrity to the protocol using digital signatures, and turns the DNS into a public key infrastructure (PKI). At the top of this PKI is a single key, the so-called Key Signing Key (KSK) for the DNS root. The current Root KSK was introduced in 2010, and has not changed since. This year, the Root KSK will be replaced for the first time ever. This event potentially has a major impact on the Internet. Thousands of DNS resolvers worldwide rely on this key to validate DNSSEC signatures, and must start using the new key, either through an automated process, or manual intervention. Failure to pick up the new key will result in resolvers becoming completely unavailable to end users. This work presents the “Root Canary”, a system to monitor and measure this event from the perspective of validating DNS resolvers for its entire nine-month duration. The system combines three active measurement platforms to have the broadest possible coverage of validating resolvers. Results will be presented in near real-time, to allow the global DNS community to act if problems arise. Furthermore, after the Root KSK rollover concludes in March 2018, we will use the recorded datasets for an in-depth analysis, from which the Internet community can draw lessons for future key rollovers