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: "length based cryptanalysis the case of thompson s group"
  Abstract: The length-based approach is a heuristic for solving randomly generated equations in groups that possess a reasonably behaved length function. We describe several improvements of the previously suggested length-based algorithms, which make them applicable to Thompson's group with significant success rates. In particular, this shows that the Shpilrain-Ushakov public key cryp- tosystem based on Thompson's group is insecure, and suggests that no practical public key cryp- tosystem based on the difficulty of solving an equation in this group can be secure.

Connected through hyperedge HE-1 (induced by source paper "heisenberg groups as platform for the aag key exchange protocol"):
  with members:
    - "non commutative digital signatures"
    - "length based attacks for certain group based encryption rewriting systems"

Connected through hyperedge HE-2 (induced by source paper "cryptanalysis of group based key agreement protocols using subgroup distance functions"):
  with members:
    - "length based attacks for certain group based encryption rewriting systems"

Connected through hyperedge HE-3 (induced by source paper "on an authentication scheme based on the root problem in the braid group"):
  with members:
    - "on the security of new key exchange protocols based on the triple decomposition problem"
    - "authentication schemes using braid groups"

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)