Electricity theft, the behavior that involves users conducting illegal operations on electrical meters to avoid individual electricity bills, is a common phenomenon in the developing countries. Considering its harmfulness to both power grids and the public, several mechanized methods have been developed to automatically recognize electricitytheft behaviors. However, these methods, which mainly assess users' electricity usage records, can be insufficient due to the diversity of theft tactics and the irregularity of user behaviors.In this paper, we propose to recognize electricity-theft behavior via multi-source data. In addition to users' electricity usage records, we analyze user behaviors by means of regional factors (non-technical loss) and climatic factors (temperature) in the corresponding transformer area. By conducting analytical experiments, we unearth several interesting patterns: for instance, electricity thieves are likely to consume much more electrical power than normal users, especially under extremely high or low temperatures. Motivated by these empirical observations, we further design a novel hierarchical framework for identifying electricity thieves. Experimental results based on a real-world dataset demonstrate that our proposed model can achieve the best performance in electricitytheft detection (e.g., at least +3.0% in terms of F0.5) compared with several baselines. Last but not least, our work has been applied by the State Grid of China and used to successfully catch electricity thieves in Hangzhou with a precision of 15% (an improvement from 0% attained by several other models the company employed) during monthly on-site investigation.

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The developing next generation (4G) mobile communication system will offer us great convenience and huge opportunities of service creation with numerous security threats. As a critical security mechanism, user authentication and key agreement (AKA) schemes have received considerable attentions in recent years. In this paper, a AKA scheme (SPAKA) based on self-certified public-key is proposed for the coming 4G system to reduce the storage, computation and communicational load of existing public-key based user authentication schemes while improving the security of 3G AKA scheme. Three authentication protocols including first-time authentication, re-authentication and handoff authentication are designed respectively for different authentication scenarios. According to the performance analysis, our approach has outperformed related schemes by providing better flexibility and scalability while maintain the expected security and efficiency. Consequently, it is more appropriate for 4G wireless system.Index Terms -Security of Wireless network, Authentication, Self-certified public-key, 4G wireless network.

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