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: "an efficient blockchain based hierarchical authentication mechanism for energy trading in v2g environment"
  Abstract: Vehicle-to-grid (V2G) networks have emerged as a new technology in modern electric power transmission networks. It allows bi-directional flow of communication and electricity between electric vehicles (EVs) and the Smart Grid (SG), in order to provide more sophisticated energy trading. However, due to the involvement of a huge amount of trading data and the presence of untrusted entities in the visiting networks, the underlying V2G infrastructure suffers from various security and privacy challenges. Although, several solutions have been proposed in the literature to address these problems, issues like lack of mutual authentication and anonymity, incapability to protect against several attack vectors, generation of huge overhead, and dependency on centralized infrastructures make security and privacy issues even more challenging. To address the above mentioned problems, in this paper, we propose a blockchain oriented hierarchical authentication mechanism for rewarding EVs. The overall process is broadly classified into the following phases: 1) System Initialization, 2) Registration, 3) Hierarchical Mutual Authentication, and 4) Consensus; wherein blockchain's distributed ledger has been employed for transaction execution in distributed V2G environments while Elliptic curve cryptography (ECC) has been used for hierarchical authentication. The designed hierarchical authentication mechanism has been employed to preserve the anonymity of EVs and support mutual authentication between EVs, charging stations (CSs) and the central aggregator (CAG). Additionally, it also supports minimal communicational and computational overheads on resource constrained EVs. Further, formal security verification of the proposed scheme on widely accepted Automated Validation of Internet Security Protocols and Applications (AVISPA) tool validates its safeness against different security attacks.

Connected through hyperedge HE-1 (induced by source paper "a review of blockchain based smart grid applications opportunities and future directions"):
  with members:
    - "stability and performance of coalitions of prosumers through diversification in the smart grid"

Connected through hyperedge HE-2 (induced by source paper "blockchain for future smart grid a comprehensive survey"):
  with members:
    - "exploring the attack surface of blockchain a systematic overview"
    - "when energy trading meets blockchain in electrical power system the state of the art"
    - "energy crowdsourcing and peer to peer energy trading in blockchain enabled smart grids"
    - "blockchain based grid operation services for transactive energy systems"
    - "blockchain technologies for smart energy systems fundamentals challenges and solutions"
    - "key management systems for smart grid advanced metering infrastructure a survey"
    - "a survey on the security of blockchain systems"
    - "a survey on security and privacy issues of bitcoin"

Connected through hyperedge HE-3 (induced by source paper "lisa a lightweight and secure authentication mechanism for smart metering infrastructure"):
  with members:
    - "blockchain based lightweight authentication mechanism for vehicular fog infrastructure"
    - "key management systems for smart grid advanced metering infrastructure a survey"

Connected through hyperedge HE-4 (induced by source paper "a lightweight and privacy preserving authentication protocol for mobile edge computing"):
  with members:
    - "blockchain based lightweight authentication mechanism for vehicular fog infrastructure"
    - "security in mobile edge caching with reinforcement learning"

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.NI(Networking and Internet Architecture)