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: "defeating the downgrade attack on identity privacy in 5g"
  Abstract: 3GPP Release 15, the first 5G standard, includes protection of user identity privacy against IMSI catchers. These protection mechanisms are based on public key encryption. Despite this protection, IMSI catching is still possible in LTE networks which opens the possibility of a downgrade attack on user identity privacy, where a fake LTE base station obtains the identity of a 5G user equipment. We propose (i) to use an existing pseudonym-based solution to protect user identity privacy of 5G user equipment against IMSI catchers in LTE and (ii) to include a mechanism for updating LTE pseudonyms in the public key encryption based 5G identity privacy procedure. The latter helps to recover from a loss of synchronization of LTE pseudonyms. Using this mechanism, pseudonyms in the user equipment and home network are automatically synchronized when the user equipment connects to 5G. Our mechanisms utilize existing LTE and 3GPP Release 15 messages and require modifications only in the user equipment and home network in order to provide identity privacy. Additionally, lawful interception requires minor patching in the serving network.

Connected through hyperedge HE-1 (induced by source paper "zipphone protecting user location privacy from cellular service providers"):
  with members:
    - "dandelion lightweight cryptocurrency networking with formal anonymity guarantees"

Connected through hyperedge HE-2 (induced by source paper "the current state of affairs in 5g security and the main remaining security challenges"):
  with members:
    - "security and protocol exploit analysis of the 5g specifications"
    - "formal analysis of 5g authentication"
    - "lte security protocol exploits and location tracking experimentation with low cost software radio"
    - "srslte an open source platform for lte evolution and experimentation"
    - "practical attacks against privacy and availability in 4g lte mobile communication systems"

Connected through hyperedge HE-3 (induced by source paper "security and protocol exploit analysis of the 5g specifications"):
  with members:
    - "formal analysis of 5g authentication"
    - "the 5g aka authentication protocol privacy"
    - "lte phy layer vulnerability analysis and testing using open source sdr tools"
    - "extending lte into the unlicensed spectrum technical analysis of the proposed variants"
    - "performance analysis of a mission critical portable lte system in targeted rf interference"
    - "lte security protocol exploits and location tracking experimentation with low cost software radio"
    - "practical attacks against privacy and availability in 4g lte mobile communication systems"
    - "five disruptive technology directions for 5g"

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)