In vehicular ad hoc networks, the exchange of safety messages plays a crucial role in transportation efficiency and safety. However, safety messages are generally only signed rather than encrypted when broadcast, which lures malicious attackers to collect sensitive and private data. Obviously, an efficient privacy-preserving signcryption mechanism is essential for the timely and correct acceptance of safety messages. Currently, most state-of-the-art mechanisms satisfy security requirements, but performance is inefficient. Therefore, in this article, we design a provably secure lightweight authentication based on elliptic curve signcryption (EPSLA) for vehicle-to-vehicle communication, which can fulfill batch unsigncryption and a feasible security communication scheme in practical scenarios. The EPSLA scheme ensures security in relation to existential unforgeability against adaptive chosen message attacks and indistinguishability against adaptive chosen ciphertext attacks under the hardness assumption of the elliptic curve discrete logarithm problem in the random oracle model. Performance analysis shows that our scheme significantly performs better than the comparison schemes.

Vehicle-to-vehicle (V2V) communications play a pivotal role in enhancing traffic efficiency and safety by exchanging safety messages. However, these messages face security threats and privacy concerns due to the nature of wireless communication and private information they contain. To address security threats and ensure privacy protection, conditional privacy-preserving authentication schemes have emerged as a primary defense to ensure message integrity and authenticity. Currently, the existing schemes either face security challenges or are impractical for the resource-constrained onboard unit (OBU). Moreover, they rely solely on digital signature or signcryption mechanisms. Considering that safety messages encompass both private and non-private information, a dynamic selection mechanism for signature or signcryption is required. In response to these challenges, this paper proposes a lightweight certificateless conditional privacy-preserving scheme (LCCPS) for V2V communications. The LCCPS scheme not only integrates both signature and signcryption within a single algorithm for the first time in V2V communications, but also ensures efficient and secure communications. The security of this scheme is proven against adaptive chosen ciphertext attacks and adaptive chosen message attacks in the random oracle model, leveraging the intractability of the elliptic curve discrete logarithm problem. The performance evaluations conducted on the OBU show that the LCCPS scheme outperforms ten comparable schemes in terms of computational overhead and power consumption, while maintaining security without increasing storage or communication overhead.

Natural answer generation is in a very clear practical significance and strong application background, which can be widely used in the field of knowledge services such as community question answering and intelligent customer service. Traditional knowledge question answering is to provide precise answer entities and neglect the defects; namely, users hope to receive a complete natural answer. In this research, we propose a novel attention-based recurrent neural network for natural answer generation, which is enhanced with multi-level copying mechanisms and question-aware loss. To generate natural answers that conform to grammar, we leverage multi-level copying mechanisms and the prediction mechanism which can copy semantic units and predict common words. Moreover, considering the problem that the generated natural answer does not match the user question, question-aware loss is introduced to make the generated target answer sequences correspond to the question. Experiments on three response generation tasks show our model to be superior in quality while being more parallelizable and requiring significantly less time to train. Our model achieves 0.727 BLEU on the SimpleQuestions response generation task, improving over the existing best results by over 0.007 BLEU. Our model has scored a significant enhancement on naturalness with up to 0.05 more than best performing baseline. The simulation results show that our method can generate grammatical and contextual natural answers according to user needs.

Attitude stability plays an important role in quadrotor aircraft. However, it is difficult to design a robust controller to precisely track a desired attitude trajectory in the presence of external disturbance. To address this problem, a nonlinear disturbance estimator with finite-time convergence is proposed to estimate external disturbance. Then, a dynamic surface control scheme based on the disturbance estimator is developed. Therefore, the compensation for external disturbance can be achieved in the designed controller. Furthermore, the L _∞ performance of transient attitude tracking error is achieved by analyzing solution of Lyapunov function. The finite-time convergence of disturbance estimation error and the asymptotical convergence of attitude tracking error of closed-loop system are rigorously proved. Finally, the numerical simulations are carried out to demonstrate the effectiveness of the developed disturbance estimator and control scheme.

This paper investigates the control problem of an unmanned surface vessel system in the presence of external disturbance. The dynamic model of an unmanned surface vessel is first introduced. Then, a nonlinear disturbance estimator is designed to estimate the external disturbance. Such an estimator ensures that the disturbance estimation error converges to zero in finite time, which means the disturbance can be compensated in finite time. Using the disturbance estimation result, a composite control technique that combines the sliding mode method and the backstepping method is developed to stabilize the position and yaw angle of the unmanned surface vessel. As a result, the tracking error is guaranteed to converge to zero asymptotically. The stability of the closed-loop system is proved based on Lyapunov theory. Furthermore, the transient norm performance of the tracking error is obtained by analyzing the selected Lyapunov function. Finally, the simulation is carried out to demonstrate the effectiveness of the proposed control scheme.