We propose a continuous-variable quantum secret sharing scheme based on multi-ring discrete modulation, which we called MR-CVQSS. In this scheme, phase shift keying (PSK)-modulated coherent states are allowed to be further discretely modulated with different amplitudes, so that these modulated coherent states can be scattered on different amplitude rings in phase space. The advantage for this multi-ring structure is that the error probability of quantum detector for discriminating discretely-modulated coherent states (DMCSs) is more lower than that of original single-ring discretely modulated CVQSS, which is beneficial for improving the performance of whole CVQSS system. We derive the security bound for MR-CVQSS against both eavesdroppers and dishonest users, and the numerical simulation shows that the performance of MR-CVQSS in terms of both maximal transmission distance and maximal available number of users can be largely improved. Moreover, security analysis shows that the modulation variance of MR-CVQSS does not need to be very small, thereby improving the signal-to-noise ratio (SNR) of whole CVQSS system.

Distributed Denial of Service attack DDoS has been one of the greatest threats to network security for years. In recent years, DDoS attackers turn to application layer, which makes DDoS attack detection systems based on net layer and transport layer lose their performance. In this layer, Web service is the most vulnerable application. In this study, we analyze the differentiation between users behaviors, as we extract two feature sequences from Web logs to represent characteristics of user behavior, and then, application layer DDoS attack detection system architecture based on feature sequences is presented. This architecture is divided into two parts. For each part, we propose detection methods, respectively. Specially, we consider users request frequency sequence as sparse vector, and then put forward a kind of classification algorithm called sparse vector decomposition and rhythm matching SVD-RM, which is based on sparse vector decomposition and rhythm matching. This algorithm is fully considering the discrepancy of different users in access behavior. A cluster algorithm with label, called L-Kmeans, is also proposed as embedded classifier in SVD-RM. Finally, we simulate four kinds of prevalent application layer DDoS attack and conduct experiments to certify the effectiveness of our methods. Experimental results show that proposed methods are good to distinguish legal users and attackers in application layer. Copyright © 2015 John Wiley & Sons, Ltd.