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 road reflections on the security of vehicular communication systems"
  Abstract: Vehicular communication (VC) systems have recently drawn the attention of industry, authorities, and academia. A consensus on the need to secure VC systems and protect the privacy of their users led to concerted efforts to design security architectures. Interestingly, the results different project contributed thus far bear extensive similarities in terms of objectives and mechanisms. As a result, this appears to be an auspicious time for setting the corner-stone of trustworthy VC systems. Nonetheless, there is a considerable distance to cover till their deployment. This paper ponders on the road ahead. First, it presents a distillation of the state of the art, covering the perceived threat model, security requirements, and basic secure VC system components. Then, it dissects predominant assumptions and design choices and considers alternatives. Under the prism of what is necessary to render secure VC systems practical, and given possible non-technical influences, the paper attempts to chart the landscape towards the deployment of secure VC systems.

Connected through hyperedge HE-1 (induced by source paper "scaling pseudonymous authentication for large mobile systems"):
  with members:
    - "efficient scalable and resilient vehicle centric certificate revocation list distribution in vanets"
    - "blockpki an automated resilient and transparent public key infrastructure"
    - "a security credential management system for v2x communications"
    - "vpkiaas a highly available and dynamically scalable vehicular public key infrastructure"
    - "rhythm a randomized hybrid scheme to hide in the mobile crowd"
    - "secmace scalable and robust identity and credential management infrastructure in vehicular communication systems"
    - "security and privacy in vehicular social networks"
    - "evaluating on demand pseudonym acquisition policies in vehicular communication systems"

Connected through hyperedge HE-2 (induced by source paper "efficient scalable and resilient vehicle centric certificate revocation list distribution in vanets"):
  with members:
    - "a security credential management system for v2x communications"
    - "rhythm a randomized hybrid scheme to hide in the mobile crowd"
    - "secmace scalable and robust identity and credential management infrastructure in vehicular communication systems"
    - "optimized certificate revocation list distribution for secure v2x communications"
    - "evaluating on demand pseudonym acquisition policies in vehicular communication systems"
    - "the key to intelligent transportation identity and credential management in vehicular communication systems"
    - "towards deploying a scalable robust vehicular identity and credential management infrastructure"
    - "secure vehicular communication systems design and architecture"

Connected through hyperedge HE-3 (induced by source paper "secmace scalable and robust identity and credential management infrastructure in vehicular communication systems"):
  with members:
    - "resilient privacy protection for location based services through decentralization"
    - "security and privacy in vehicular social networks"
    - "evaluating on demand pseudonym acquisition policies in vehicular communication systems"
    - "the key to intelligent transportation identity and credential management in vehicular communication systems"
    - "towards deploying a scalable robust vehicular identity and credential management infrastructure"
    - "vespa vehicular security and privacy preserving architecture"
    - "secure vehicular communication systems implementation performance and research challenges"
    - "impact of vehicular communications security on transportation safety"

Connected through hyperedge HE-4 (induced by source paper "evaluating on demand pseudonym acquisition policies in vehicular communication systems"):
  with members:
    - "the key to intelligent transportation identity and credential management in vehicular communication systems"
    - "towards deploying a scalable robust vehicular identity and credential management infrastructure"
    - "vespa vehicular security and privacy preserving architecture"
    - "secure vehicular communication systems design and architecture"

Connected through hyperedge HE-5 (induced by source paper "the key to intelligent transportation identity and credential management in vehicular communication systems"):
  with members:
    - "towards deploying a scalable robust vehicular identity and credential management infrastructure"
    - "vespa vehicular security and privacy preserving architecture"
    - "impact of vehicular communications security on transportation safety"
    - "secure vehicular communication systems design and architecture"

Connected through hyperedge HE-6 (induced by source paper "towards deploying a scalable robust vehicular identity and credential management infrastructure"):
  with members:
    - "vespa vehicular security and privacy preserving architecture"
    - "impact of vehicular communications security on transportation safety"
    - "secure vehicular communication systems design and architecture"

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)