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: "on the security of 2 key triple des"
  Abstract: This paper reconsiders the security offered by 2-key triple DES, an encryption technique that remains widely used despite recently being de-standardised by NIST. A generalisation of the 1990 van Oorschot-Wiener attack is described, constituting the first advance in cryptanalysis of 2-key triple DES since 1990. We give further attack enhancements that together imply that the widely used estimate that 2-key triple DES provides 80 bits of security can no longer be regarded as conservative; the widely stated assertion that the scheme is secure as long as the key is changed regularly is also challenged. The main conclusion is that, whilst not completely broken, the margin of safety for 2-key triple DES is slim, and efforts to replace it, at least with its 3-key variant, should be pursued with some urgency.

Connected through hyperedge HE-1 (induced by source paper "verifying software vulnerabilities in iot cryptographic protocols"):
  with members:
    - "v fuzz vulnerability oriented evolutionary fuzzing"
    - "improving function coverage with munch a hybrid fuzzing and directed symbolic execution approach"
    - "extracting and verifying cryptographic models from c protocol code by symbolic execution"
    - "smt based bounded model checking for embedded ansi c software"

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)