human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "cyber security in smart grid survey and challenges"
  Abstract: Abstract   Smart grid uses the power of information technology to intelligently deliver energy by using a two-way communication and wisely meet the environmental requirements by facilitating the integration of green technologies. The inherent weakness of communication technology has exposed the system to numerous security threats. Several survey papers have discussed these problems and their countermeasures. However, most of these papers classified attacks based on confidentiality, integrity, and availability, but they excluded the accountability. In addition, the existing countermeasures focus on countering some specific attacks or protecting some specific components, but there is no global approach to secure the entire system. In this paper, we review the security requirements, provide descriptions of several severe cyber-attacks, and propose a cyber-security strategy to detect and counter these attacks. Lastly, we provide some future research directions.

Connected through hyperedge HE-1 (induced by source paper "deep learning based intrusion detection system for advanced metering infrastructure"):
  with members:
    - "primary user emulation attacks a detection technique based on kalman filter"
    - "an overview of gradient descent optimization algorithms"
    - "tensorflow a system for large scale machine learning"
    - "a new secure network architecture to increase security among virtual machines in cloud computing"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.CR(Cryptography and Security)