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: "the problem with the surf scheme"
  Abstract: There is a serious problem with one of the assumptions made in the security proof of the SURF scheme. This problem turns out to be easy in the regime of parameters needed for the SURF scheme to work. #R##N#We give afterwards the old version of the paper for the reader's convenience.

Connected through hyperedge HE-1 (induced by source paper "ternary syndrome decoding with large weight"):
  with members:
    - "wave a new code based signature scheme"
    - "generalization of the ball collision algorithm"

Connected through hyperedge HE-2 (induced by source paper "wave a new family of trapdoor one way preimage sampleable functions based on codes"):
  with members:
    - "ternary syndrome decoding with large weight"
    - "two attacks on rank metric code based schemes ranksign and an identity based encryption scheme"
    - "using ldgm codes and sparse syndromes to achieve digital signatures"

Connected through hyperedge HE-3 (induced by source paper "wave a new code based signature scheme"):
  with members:
    - "ternary syndrome decoding with large weight"
    - "using ldgm codes and sparse syndromes to achieve digital signatures"

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)