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: "a survey of symbolic methods for establishing equivalence based properties in cryptographic protocols"
  Abstract: Cryptographic protocols aim at securing communications over insecure networks such as the Internet, where dishonest users may listen to communications and interfere with them. A secure communication has a different meaning depending on the underlying application. It ranges from the confidentiality of a data to e.g. verifiability in electronic voting systems. Another example of a security notion is privacy. #R##N#Formal symbolic models have proved their usefulness for analysing the security of protocols. Until quite recently, most results focused on trace properties like confidentiality or authentication. There are however several security properties, which cannot be defined (or cannot be naturally defined) as trace properties and require a notion of behavioural equivalence. Typical examples are anonymity, and privacy related properties. During the last decade, several results and verification tools have been developed to analyse equivalence-based security properties. #R##N#We propose here a synthesis of decidability and undecidability results for equivalence-based security properties. Moreover, we give an overview of existing verification tools that may be used to verify equivalence-based security properties.

Connected through hyperedge HE-1 (induced by source paper "journey beyond full abstraction exploring robust property preservation for secure compilation"):
  with members:
    - "when good components go bad formally secure compilation despite dynamic compromise"
    - "a reduced semantics for deciding trace equivalence"
    - "beyond good and evil formalizing the security guarantees of compartmentalizing compilation"
    - "the applied pi calculus mobile values new names and secure communication"

Connected through hyperedge HE-2 (induced by source paper "por for security protocol equivalences beyond action determinism"):
  with members:
    - "a survey of symbolic execution techniques"
    - "partial order reduction for security protocols"

Connected through hyperedge HE-3 (induced by source paper "improving automated symbolic analysis for e voting protocols a method based on sufficient conditions for ballot secrecy"):
  with members:
    - "formal analysis of 5g authentication"
    - "a type system for privacy properties technical report"

Connected through hyperedge HE-4 (induced by source paper "formal analysis of v2x revocation protocols"):
  with members:
    - "survey on misbehavior detection in cooperative intelligent transportation systems"
    - "secure vehicular communication systems design and architecture"

Connected through hyperedge HE-5 (induced by source paper "a method for unbounded verification of privacy type properties"):
  with members:
    - "formal analysis of 5g authentication"
    - "formal computational unlinkability proofs of rfid protocols"

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)