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: "mof bc a memory optimized and flexible blockchain for large scale networks"
  Abstract: BlockChain (BC) immutability ensures BC resilience against modification or removal of the stored data. In large scale networks like the Internet of Things (IoT), however, this feature significantly increases BC storage size and raises privacy challenges. In this paper, we propose a Memory Optimized and Flexible BC (MOF-BC) that enables the IoT users and service providers to remove or summarize their transactions and age their data and to exercise the "right to be forgotten". To increase privacy, a user may employ multiple keys for different transactions. To allow for the removal of stored transactions, all keys would need to be stored which complicates key management and storage. MOF-BC introduces the notion of a Generator Verifier (GV) which is a signed hash of a Generator Verifier Secret (GVS). The GV changes for each transaction to provide privacy yet is signed by a unique key, thus minimizing the information that needs to be stored. A flexible transaction fee model and a reward mechanism is proposed to incentivize users to participate in optimizing memory consumption. Qualitative security and privacy analysis demonstrates that MOF-BC is resilient against several security attacks. Evaluation results show that MOF-BC decreases BC memory consumption by up to 25\% and the user cost by more than two orders of magnitude compared to conventional BC instantiations.

Connected through hyperedge HE-1 (induced by source paper "blockchain for internet of things a survey"):
  with members:
    - "an overview on smart contracts challenges advances and platforms"
    - "repchain a reputation based secure fast and high incentive blockchain system via sharding"
    - "uav communications for 5g and beyond recent advances and future trends"
    - "big data analytics for large scale wireless networks challenges and opportunities"
    - "big data analytics for manufacturing internet of things opportunities challenges and enabling technologies"
    - "analysis of the xrp ledger consensus protocol"
    - "sabre protecting bitcoin against routing attacks"
    - "how to make a digital currency on a blockchain stable"

Connected through hyperedge HE-2 (induced by source paper "a journey in applying blockchain for cyberphysical systems"):
  with members:
    - "a trust architecture for blockchain in iot"
    - "trustchain trust management in blockchain and iot supported supply chains"
    - "idmob iot data marketplace on blockchain"
    - "b fica blockchain based framework for auto insurance claim and adjudication"
    - "on the activity privacy of blockchain for iot"
    - "blockchain a distributed solution to automotive security and privacy"
    - "blockchain in internet of things challenges and solutions"

Connected through hyperedge HE-3 (induced by source paper "blockchain mutability challenges and proposed solutions"):
  with members:
    - "redactable blockchain in the permissionless setting"
    - "blockchains consensus protocols in the wild"
    - "when the cookie meets the blockchain privacy risks of web payments via cryptocurrencies"
    - "an empirical analysis of smart contracts platforms applications and design patterns"
    - "enigma decentralized computation platform with guaranteed privacy"
    - "bitcoin transaction graph analysis"
    - "deanonymisation of clients in bitcoin p2p network"

Connected through hyperedge HE-4 (induced by source paper "impact of consensus on appendable block blockchain for iot"):
  with members:
    - "the ico phenomenon and its relationships with ethereum smart contract environment"
    - "a survey on security and privacy issues of bitcoin"
    - "privacy preserving and efficient aggregation based on blockchain for power grid communications in smart communities"
    - "blockchain a distributed solution to automotive security and privacy"
    - "be selfish and avoid dilemmas fork after withholding faw attacks on bitcoin"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-5 (induced by source paper "on the activity privacy of blockchain for iot"):
  with members:
    - "a survey on security and privacy issues of bitcoin"
    - "lsb a lightweight scalable blockchain for iot security and privacy"
    - "a smart home is no castle privacy vulnerabilities of encrypted iot traffic"
    - "blockchain a distributed solution to automotive security and privacy"
    - "iot sentinel demo automated device type identification for security enforcement in iot"

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)