human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "when energy trading meets blockchain in electrical power system the state of the art"):
  Abstract: With the rapid growth of renewable energy resources, the energy trading began to shift from centralized to distributed manner. Blockchain, as a distributed public ledger technology, has been widely adopted to design new energy trading schemes. However, there are many challenging issues for blockchain-based energy trading, i.e., low efficiency, high transaction cost, security & privacy issues. To tackle with the above challenges, many solutions have been proposed. In this survey, the blockchain-based energy trading in electrical power system is thoroughly investigated. Firstly, the challenges in blockchain-based energy trading are identified. Then, the existing energy trading schemes are studied and classified into three categories based on their main focus: energy transaction, consensus mechanism, and system optimization. And each category is presented in detail. Although existing schemes can meet the specific energy trading requirements, there are still many unsolved problems. Finally, the discussion and future directions are given.

Includes members:
  Member "blockchain technologies for the internet of things research issues and challenges":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "the security reference architecture for blockchains towards a standardized model for studying vulnerabilities threats and defenses")
  Member "decentralized p2p energy trading under network constraints in a low voltage network":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "peer to peer trading in electricity networks an overview")
  Member "on the applicability of distributed ledger architectures to peer to peer energy trading framework":
    also connected through other hyperedges:
      (none)
  Member "peer to peer and community based markets a comprehensive review":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "blockchain technologies for smart energy systems fundamentals challenges and solutions")
  Member "peer to peer energytrade a distributed private energy trading platform":
    also connected through other hyperedges:
      (none)
  Member "secure and privacy friendly local electricity trading and billing in smart grid":
    also connected through other hyperedges:
      (none)
  Member "peer to peer energy trading with sustainable user participation a game theoretic approach":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "peer to peer trading in electricity networks an overview")
  Member "privacy preserving and efficient aggregation based on blockchain for power grid communications in smart communities":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "blockchain for 5g and beyond networks a state of the art survey")

Question: Please tell me which class the source paper 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)