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: "a diversity based substation cyber defense strategy utilizing coloring games"
  Abstract: Growing cybersecurity risks in the power grid require that utilities implement a variety of security mechanisms (SMs), including VPNs, firewalls, authentication, and access control mechanisms. While these mechanisms provide some level of defense, they also may contain software vulnerabilities which allow an attack to bypass their protection. Because the same SM type is often used to protect a large number of substations, a single vulnerability could enable a coordinated attack by simultaneously targeting many substations. To protect against such an attack, utilities can adopt a strategy to use a diverse set of SMs, such that the impact from a vulnerability in any SM is minimized. This paper introduces a game-theoretic graph coloring technique to determine the optimal allocation of SM diversity that minimizes the impact of security vulnerabilities to the grid. This paper demonstrates that the proposed approach provides a Nash equilibrium solution. Furthermore, the technique is demonstrated against cyber-physical models for both IEEE-14 and IEEE-118 bus systems, and compared with other non-strategic diversity allocation methods to demonstrate its effectiveness.

Connected through hyperedge HE-1 (induced by source paper "react reactive resilience for critical infrastructures using graph coloring techniques"):
  with members:
    - "nonlinear negotiation approaches for complex network optimization a study inspired by wi fi channel assignment"
    - "spectrum graph coloring to improve wi fi channel assignment in a real world scenario via edge contraction"
    - "spectrum graph coloring and applications to wi fi channel assignment"
    - "power grid defense against malicious cascading failure"
    - "belief propagation for min cost network flow convergence and correctness"

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)