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: "survey of sybil attacks in social networks"
  Abstract: This paper reviews the Sybil attack in social networks, which has the potential to compromise the whole distributed network. In the Sybil attack, the malicious user claims multiple identities to compromise the network. Sybil attacks can be used to change the overall ranking in voting applications, bad-mouth an opinion, access resources or to break the trust mechanism behind a P2P network. In this paper, different defense mechanisms used to mitigate Sybil attacks are also reviewed.

Connected through hyperedge HE-1 (induced by source paper "multiparty probability computation and verification"):
  with members:
    - "a review of man in the middle attacks"
    - "oblivious transfer protocol with verification"
    - "generating primes using partitions"
    - "a survey of p2p network security"
    - "the piggy bank cryptographic trope"

Connected through hyperedge HE-2 (induced by source paper "coding side information for implementing cubic transformation"):
  with members:
    - "a review of man in the middle attacks"
    - "a survey of p2p network security"
    - "the piggy bank cryptographic trope"

Connected through hyperedge HE-3 (induced by source paper "connectivity in social networks"):
  with members:
    - "a review of man in the middle attacks"
    - "a survey of p2p network security"

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)