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: "cryptocurrencies without proof of work"
  Abstract: We study decentralized cryptocurrency protocols in which the participants do not deplete physical scarce resources. Such protocols commonly rely on Proof of Stake, i.e., on mechanisms that extend voting power to the stakeholders of the system. We offer analysis of existing protocols that have a substantial amount of popularity. We then present our novel pure Proof of Stake protocols, and argue that they help in mitigating problems that the existing protocols exhibit.

Connected through hyperedge HE-1 (induced by source paper "blockchain consensus algorithms a survey"):
  with members:
    - "a survey on consensus mechanisms and mining strategy management in blockchain networks"
    - "blockchains consensus protocols in the wild"
    - "consensus in the age of blockchains"
    - "casper the friendly finality gadget"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-2 (induced by source paper "blockchain consensuses algorithms a survey"):
  with members:
    - "a survey on consensus mechanisms and mining strategy management in blockchain networks"
    - "blockchains consensus protocols in the wild"
    - "consensus in the age of blockchains"
    - "casper the friendly finality gadget"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-3 (induced by source paper "infnote a decentralized information sharing platform based on blockchain"):
  with members:
    - "network traffic obfuscation and automated internet censorship"
    - "ipfs content addressed versioned p2p file system"
    - "dimming the internet detecting throttling as a mechanism of censorship in iran"

Connected through hyperedge HE-4 (induced by source paper "the security reference architecture for blockchains towards a standardized model for studying vulnerabilities threats and defenses"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "a survey on ethereum systems security vulnerabilities attacks and defenses"
    - "security and privacy on blockchain"
    - "deconstructing blockchains a comprehensive survey on consensus membership and structure"
    - "truffle tests for free replaying ethereum smart contracts for transparency"
    - "blockchain technologies for the internet of things research issues and challenges"
    - "exploring the attack surface of blockchain a systematic overview"
    - "strongchain transparent and collaborative proof of work consensus"

Connected through hyperedge HE-5 (induced by source paper "a survey on applications of game theory in blockchain"):
  with members:
    - "a survey on consensus mechanisms and mining strategy management in blockchain networks"
    - "security services using blockchains a state of the art survey"
    - "blockchain governance game"
    - "exchange of renewable energy among prosumers using blockchain with dynamic pricing"
    - "game of coins"
    - "delayed blockchain protocols"
    - "reward sharing schemes for stake pools"
    - "a survey on the security of blockchain systems"

Connected through hyperedge HE-6 (induced by source paper "presto a systematic framework for blockchain consensus protocols"):
  with members:
    - "oceanic games centralization risks and incentives in blockchain mining"
    - "weighted voting on the blockchain improving consensus in proof of stake protocols"
    - "blockchain trilemma solver algorand has dilemma over undecidable messages"
    - "blockchain technologies for the internet of things research issues and challenges"
    - "strongchain transparent and collaborative proof of work consensus"
    - "a survey on consensus mechanisms and mining strategy management in blockchain networks"
    - "sok tools for game theoretic models of security for cryptocurrencies"
    - "incentives in ethereum s hybrid casper protocol"

Connected through hyperedge HE-7 (induced by source paper "a security reference architecture for blockchains"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "strongchain transparent and collaborative proof of work consensus"
    - "insight into insiders and it a survey of insider threat taxonomies analysis modeling and countermeasures"
    - "dfinity technology overview series consensus system"
    - "short paper towards more reliable bitcoin timestamps"
    - "the latest gossip on bft consensus"
    - "finding the greedy prodigal and suicidal contracts at scale"
    - "sabre protecting bitcoin against routing attacks"

Connected through hyperedge HE-8 (induced by source paper "sok of used cryptography in blockchain"):
  with members:
    - "sef a secure fountain architecture for slashing storage costs in blockchains"
    - "dfinity technology overview series consensus system"
    - "celer network bring internet scale to every blockchain"
    - "raziel private and verifiable smart contracts on blockchains"
    - "blendcac a blockchain enabled decentralized capability based access control for iots"
    - "hyperledger fabric a distributed operating system for permissioned blockchains"
    - "a survey on security and privacy issues of bitcoin"
    - "privacy preserving and efficient aggregation based on blockchain for power grid communications in smart communities"

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)