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: "optimal selfish mining strategies in bitcoin"
  Abstract: Bitcoin is a decentralized crypto-currency, and an accompanying protocol, created in 2008. Bitcoin nodes continuously generate and propagate blocks---collections of newly approved transactions that are added to Bitcoin's ledger. Block creation requires nodes to invest computational resources, but also carries a reward in the form of bitcoins that are paid to the creator. While the protocol requires nodes to quickly distribute newly created blocks, strong nodes can in fact gain higher payoffs by withholding blocks they create and selectively postponing their publication. The existence of such selfish mining attacks was first reported by Eyal and Sirer, who have demonstrated a specific deviation from the standard protocol (a strategy that we name SM1). #R##N#In this paper we extend the underlying model for selfish mining attacks, and provide an algorithm to find $\epsilon$-optimal policies for attackers within the model, as well as tight upper bounds on the revenue of optimal policies. As a consequence, we are able to provide lower bounds on the computational power an attacker needs in order to benefit from selfish mining. We find that the profit threshold -- the minimal fraction of resources required for a profitable attack -- is strictly lower than the one induced by the SM1 scheme. Indeed, the policies given by our algorithm dominate SM1, by better regulating attack-withdrawals. #R##N#Using our algorithm, we show that Eyal and Sirer's suggested countermeasure to selfish mining is slightly less effective than previously conjectured. Next, we gain insight into selfish mining in the presence of communication delays, and show that, under a model that accounts for delays, the profit threshold vanishes, and even small attackers have incentive to occasionally deviate from the protocol. We conclude with observations regarding the combined power of selfish mining and double spending attacks.

Connected through hyperedge HE-1 (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"
    - "bitcoin ng a scalable blockchain protocol"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-2 (induced by source paper "coalition safe equilibria with virtual payoffs"):
  with members:
    - "presto a systematic framework for blockchain consensus protocols"
    - "squirrl automating attack discovery on blockchain incentive mechanisms with deep reinforcement learning"
    - "the gap game"
    - "blockchain mining games"
    - "majority is not enough bitcoin mining is vulnerable"
    - "on bitcoin and red balloons"
    - "an almost surely terminating polynomial protocol for asynchronous byzantine agreement with optimal resilience"

Connected through hyperedge HE-3 (induced by source paper "double spend counterattacks threat of retaliation in proof of work systems"):
  with members:
    - "oceanic games centralization risks and incentives in blockchain mining"
    - "mind the mining"
    - "bitcoin a natural oligopoly"
    - "analysis of hashrate based double spending"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-4 (induced by source paper "modeling the impact of network connectivity on consensus security of proof of work blockchain"):
  with members:
    - "a survey of distributed consensus protocols for blockchain networks"
    - "decentralization in bitcoin and ethereum networks"
    - "consensus in the age of blockchains"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-5 (induced by source paper "blockchain using proof of interaction"):
  with members:
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-6 (induced by source paper "rtm blockchain that support revocable transaction model"):
  with members:
    - "analysis of hashrate based double spending"

Connected through hyperedge HE-7 (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-8 (induced by source paper "exploring the attack surface of blockchain a systematic overview"):
  with members:
    - "scalable byzantine consensus via hardware assisted secret sharing"
    - "security services using blockchains a state of the art survey"
    - "a survey on the security of blockchain systems"
    - "an empirical analysis of anonymity in zcash"
    - "towards blockchain driven secure and transparent audit logs"
    - "end to end analysis of in browser cryptojacking"
    - "linbft linear communication byzantine fault tolerance for public blockchains"
    - "a survey on security and privacy issues of bitcoin"

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)