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: "towards the automated verification of cyber physical security protocols bounding the number of timed intruders"
  Abstract: Timed Intruder Models have been proposed for the verification of Cyber-Physical Security Protocols (CPSP) amending the traditional Dolev-Yao intruder to obey the physical restrictions of the environment. Since to learn a message, a Timed Intruder needs to wait for a message to arrive, mounting an attack may depend on where Timed Intruders are. It may well be the case that in the presence of a great number of intruders there is no attack, but there is an attack in the presence of a small number of well placed intruders. Therefore, a major challenge for the automated verification of CPSP is to determine how many Timed Intruders to use and where should they be placed. This paper answers this question by showing it is enough to use the same number of Timed Intruders as the number of participants. We also report on some preliminary experimental results in discovering attacks in CPSP.

Connected through hyperedge HE-1 (induced by source paper "time computational complexity and probability in the analysis of distance bounding protocols"):
  with members:
    - "automatic analysis of distance bounding protocols"
    - "timed analysis of security protocols"

Connected through hyperedge HE-2 (induced by source paper "a formal approach to cyber physical attacks"):
  with members:
    - "state of the art of cyber physical systems security an automatic control perspective"
    - "a calculus of cyber physical systems"
    - "cpdy extending the dolev yao attacker with physical layer interactions"

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)