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: "evaluating on demand pseudonym acquisition policies in vehicular communication systems"
  Abstract: Standardization and harmonization efforts have reached a consensus towards using a special-purpose Vehicular Public-Key Infrastructure (VPKI) in upcoming Vehicular Communication (VC) systems. However, there are still several technical challenges with no conclusive answers; one such an important yet open challenge is the acquisition of short-term credentials, pseudonym: how should each vehicle interact with the VPKI, e.g., how frequently and for how long? Should each vehicle itself determine the pseudonym lifetime? Answering these questions is far from trivial. Each choice can affect both the user privacy and the system performance and possibly, as a result, its security. In this paper, we make a novel systematic effort to address this multifaceted question. We craft three generally applicable policies and experimentally evaluate the VPKI system performance, leveraging two large-scale mobility datasets. We consider the most promising, in terms of efficiency, pseudonym acquisition policies; we find that within this class of policies, the most promising policy in terms of privacy protection can be supported with moderate overhead. Moreover, in all cases, this work is the first to provide tangible evidence that the state-of-the-art VPKI can serve sizable areas or domain with modest computing resources.

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"
    - "the key to intelligent transportation identity and credential management 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"
    - "the key to intelligent transportation identity and credential management in vehicular communication systems"
    - "towards deploying a scalable robust vehicular identity and credential management infrastructure"
    - "on the road reflections on the security of vehicular communication systems"
    - "secure vehicular communication systems design and architecture"

Connected through hyperedge HE-3 (induced by source paper "vpkiaas a highly available and dynamically scalable vehicular public key infrastructure"):
  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"
    - "the key to intelligent transportation identity and credential management in vehicular communication systems"
    - "towards deploying a scalable robust vehicular identity and credential management infrastructure"

Connected through hyperedge HE-4 (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"
    - "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"
    - "on the road reflections on the security of vehicular communication systems"
    - "secure vehicular communication systems implementation performance and research challenges"
    - "impact of vehicular communications security on transportation safety"

Connected through hyperedge HE-5 (induced by source paper "rhythm a randomized hybrid scheme to hide in the mobile crowd"):
  with members:
    - "secmace scalable and robust identity and credential management infrastructure in vehicular communication systems"
    - "the key to intelligent transportation identity and credential management in vehicular communication systems"

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)