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: "bitcoin ng a scalable blockchain protocol"
  Abstract: Cryptocurrencies, based on and led by Bitcoin, have shown promise as infrastructure for pseudonymous online payments, cheap remittance, trustless digital asset exchange, and smart contracts. However, Bitcoin-derived blockchain protocols have inherent scalability limits that trade-off between throughput and latency and withhold the realization of this potential. #R##N#This paper presents Bitcoin-NG, a new blockchain protocol designed to scale. Based on Bitcoin's blockchain protocol, Bitcoin-NG is Byzantine fault tolerant, is robust to extreme churn, and shares the same trust model obviating qualitative changes to the ecosystem. #R##N#In addition to Bitcoin-NG, we introduce several novel metrics of interest in quantifying the security and efficiency of Bitcoin-like blockchain protocols. We implement Bitcoin-NG and perform large-scale experiments at 15% the size of the operational Bitcoin system, using unchanged clients of both protocols. These experiments demonstrate that Bitcoin-NG scales optimally, with bandwidth limited only by the capacity of the individual nodes and latency limited only by the propagation time of the network.

Connected through hyperedge HE-1 (induced by source paper "surface a practical blockchain consensus algorithm for real world networks"):
  with members:
    - "rationality is self defeating in permissionless systems"
    - "dfinity technology overview series consensus system"
    - "hotstuff bft consensus in the lens of blockchain"
    - "deconstructing the blockchain to approach physical limits"
    - "scaling nakamoto consensus to thousands of transactions per second"
    - "transaction propagation on permissionless blockchains incentive and routing mechanisms"
    - "implicit consensus blockchain with unbounded throughput"
    - "chainspace a sharded smart contracts platform"

Connected through hyperedge HE-2 (induced by source paper "hushrelay a privacy preserving efficient and scalable routing algorithm for off chain payments"):
  with members:
    - "concurrency and privacy with payment channel networks"
    - "topological analysis of bitcoin s lightning network"
    - "ant routing algorithm for the lightning network"
    - "routing cryptocurrency with the spider network"
    - "consensus in the age of blockchains"
    - "towards a concurrent and distributed route selection for payment channel networks"
    - "casper the friendly finality gadget"
    - "settling payments fast and private efficient decentralized routing for path based transactions"

Connected through hyperedge HE-3 (induced by source paper "incentive analysis of bitcoin ng revisited"):
  with members:
    - "analysis of nakamoto consensus revisited"
    - "scaling nakamoto consensus to thousands of transactions per second"
    - "ohie blockchain scaling made simple"
    - "the gap game"
    - "enhancing bitcoin security and performance with strong consistency via collective signing"
    - "solida a blockchain protocol based on reconfigurable byzantine consensus"
    - "optimal selfish mining strategies in bitcoin"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-4 (induced by source paper "attacking the defi ecosystem with flash loans for fun and profit"):
  with members:
    - "libra fair order matching for electronic financial exchanges"
    - "flash boys 2 0 frontrunning transaction reordering and consensus instability in decentralized exchanges"
    - "harvey a greybox fuzzer for smart contracts"
    - "contractfuzzer fuzzing smart contracts for vulnerability detection"
    - "securify practical security analysis of smart contracts"

Connected through hyperedge HE-5 (induced by source paper "verifiable and auditable digital interchange framework"):
  with members:
    - "hyperledger fabric a distributed operating system for permissioned blockchains"
    - "sprites and state channels payment networks that go faster than lightning"
    - "chainspace a sharded smart contracts platform"
    - "performance characterization of a commercial video streaming service"
    - "centrally banked cryptocurrencies"

Connected through hyperedge HE-6 (induced by source paper "resilientdb global scale resilient blockchain fabric"):
  with members:
    - "proof of execution reaching consensus through fault tolerant speculation"
    - "towards scaling blockchain systems via sharding"
    - "blockbench a framework for analyzing private blockchains"
    - "enhancing bitcoin security and performance with strong consistency via collective signing"

Connected through hyperedge HE-7 (induced by source paper "continuous time analysis of the bitcoin and prism backbone protocols"):
  with members:
    - "on analysis of the bitcoin and prism backbone protocols"
    - "deconstructing the blockchain to approach physical limits"
    - "scaling nakamoto consensus to thousands of transactions per second"
    - "the balance attack against proof of work blockchains the r3 testbed as an example"

Connected through hyperedge HE-8 (induced by source paper "fail safe watchtowers and short lived assertions for payment channels"):
  with members:
    - "concurrency and privacy with payment channel networks"
    - "towards secure and efficient payment channels"
    - "teechain a secure asynchronous blockchain payment network"

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)