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Strong deviations in the finite temperature atomic structure of halide perovskites from their average geometry can have profound impacts on optoelectronic and other device-relevant properties. Detailed mechanistic understandings of these structural fluctuations and their consequences remain, however, limited by the experimental and theoretical challenges involved in characterizing strongly anharmonic vibrational characteristics and their impact on other properties. We overcome some of these challenges by a theoretical characterization of the vibrational interactions that occur among the atoms in the prototypical cubic CsPbBr3. Our investigation based on first-principles molecular dynamics calculations finds that the motions of neighboring Cs–Br atoms interlock, which appears as the most likely Cs–Br distance being significantly shorter than what is inferred from an ideal cubic structure. This form of dynamic Cs–Br coupling coincides with very shallow dynamic potential wells for Br motions that occur across a locally and dynamically disordered energy landscape. We reveal an interesting dynamic coupling mechanism among the atoms within the nominal unit cell of cubic CsPbBr3and quantify the important local structural fluctuations on an atomic scale.

The rapid development of containerization technology comes with remarkable benefits for developers and operation teams. Container solutions allow building very flexible software infrastructures. Although lots of efforts have been devoted to enhancing containerization security, containerized environments still have a huge attack surface. Completely avoiding severe security issues have so far not been possible to achieve. However, the security problems due to vulnerabilities in for instance kernels, can be largely reduced if the container privileges are as restricted as possible. Mandatory access control is an efficient way to achieve this using for instance AppArmor. As manual AppArmor generation is tedious and error prone, automatic generation of protection profile is necessary. In previous research, a new tool for tight AppArmor profile generation was presented. In this paper we show how, in a system setting, such tool can be combined with container service testing, to provide a cloud based container service for automatic AppArmore profile generation. We present solutions for profile generation both for centrally collected and generated container logs and for log collection through a local agent. To evaluate the effectiveness of the profile generation service, we enable it on a widely used containerized web service to generate profiles and test them with real-world attacks. We generate an exploit database with 11 exploits harmful to the tested web service. These exploits are sifted from the 56 exploits of Exploit-db targeting the tested web service’s software. We launch these exploits on the web service protected by the profile. The results show that the proposed profile generation service improves the test web service’s overall security a lot compared to using the default Docker security profile. This together with the very user friendly and robust principle for setting up and running the service, clearly indicates that the approach is an important step for improving container security in real deployments.

Authentication codes are used to protect communication against a malicious adversary. In this paper we investigate unconditionally secure multiround authentication schemes. In a multiround scheme a message is authenticated by passing back and forth several codewords between the sender and receiver. We define a multiround authentication model and show how to calculate the probability of a successful attack for this model. We prove the security for a 3-round scheme and give a construction for the 3-round scheme based on Reed-Solomom codes. This construction has a very small key size for even extremely large messages. Furthermore, a secure scheme for an arbitrary number of rounds is given. We give a new upper bound for the keys size of an n-round scheme.

Group authentication schemes as introduced by Boyd and by Desmedt and Frankel are cryptographic schemes in which only certain designated groups can provide messages with authentication information. In this paper we study unconditionally secure group authentication schemes based on linear perfect secret sharing and authentication schemes, for which we give expressions for the probabilities of successful attacks. Furthermore, we give a construction that uses maximum rank distance codes.