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: "security risk analysis in peer 2 peer system an approach towards surmounting security challenges"
  Abstract: P2P networking has become a promising technology and has achieved popularity as a mechanism for users to share files without the need for centralized servers. The rapid growth of P2P networks beginning with Kaza, Lime wire, Napsters, E-donkey, Gnutella etc makes them an attractive target to the creators of viruses and other security threats. This paper describes the major security issues on P2P networks (Viruses and worms) and presents the study of propagation mechanisms. In particular, the paper explores different P2P viruses and worms, their propagation methodology, outlines the challenges, and evaluates how P2P worms affect the network. The experimental results obtained will provide new direction in surmounting the security concerns in P2P Networks Index Terms — P2P, Viruses, Worms, Simulators, Propagation.

Connected through hyperedge HE-1 (induced by source paper "sit a lightweight encryption algorithm for secure internet of things"):
  with members:
    - "security analysis of secure force algorithm for wireless sensor networks"
    - "peer to peer network simulators an analytical review"
    - "symmetric algorithm survey a comparative analysis"
    - "internet of things iot a vision architectural elements and future directions"

Connected through hyperedge HE-2 (induced by source paper "security analysis of secure force algorithm for wireless sensor networks"):
  with members:
    - "peer to peer network simulators an analytical review"
    - "symmetric algorithm survey a comparative analysis"

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)