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 "the use of smart contracts and challenges"):
  Abstract: In December 2017, "CryptoKitties", a game on the Ethereum blockchain became an instant success shortly after its launch. It attracted 180,000 users with over $20 million of spend in Ether, and was at one point taking up 12% of all Ethereum transactions. #R##N#Technically speaking, "CryptoKitties" is a smart contract - a piece of code with storage capability that resides on a blockchain. Smart contracts are gaining increasing popularity in recent years. We present a comprehensive review of smart contracts with a focus on existing applications and challenges they face. We have covered the smart contract mechanisms, promising use cases, as well as relevant research work and the open issues.

Includes members:
  Member "a first look at identity management schemes on the blockchain":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "security privacy in iot using machine learning blockchain threats countermeasures")
  Member "blockchain based proxy re encryption scheme for secure iot data sharing":
    also connected through other hyperedges:
      (none)
  Member "smart contract slas for dense small cell as a service":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "smart contract based secure spectrum sharing in multi operators wireless communication networks")
  Member "blockchain based smart contracts a systematic mapping study":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "an overview on smart contracts challenges advances and platforms")
  Member "secure and trustable electronic medical records sharing using blockchain":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "attribute based multi signature and encryption for ehr management a blockchain based solution")
  Member "towards an ontology driven blockchain design for supply chain provenance":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "the security reference architecture for blockchains towards a standardized model for studying vulnerabilities threats and defenses")

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.CY(Computers and Society)