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: "block arrivals in the bitcoin blockchain"
  Abstract: Bitcoin is a electronic payment system where payment transactions are verified and stored in a data structure called the blockchain. Bitcoin miners work individually to solve a computationally intensive problem, and with each solution a Bitcoin block is generated, resulting in a new arrival to the blockchain. The difficulty of the computational problem is updated every 2,016 blocks in order to control the rate at which blocks are generated. In the original Bitcoin paper, it was suggested that the blockchain arrivals occur according to a homogeneous Poisson process. Based on blockchain block arrival data and stochastic analysis of the block arrival process, we demonstrate that this is not the case. We present a refined mathematical model for block arrivals, focusing on both the block arrivals during a period of constant difficulty and how the difficulty level evolves over time.

Connected through hyperedge HE-1 (induced by source paper "all that glitters is not bitcoin unveiling the centralized nature of the btc ip network"):
  with members:
    - "decentralization in bitcoin and ethereum networks"
    - "digging into browser based crypto mining"
    - "txprobe discovering bitcoin s network topology using orphan transactions"
    - "an evaluation of the security of the bitcoin peer to peer network"

Connected through hyperedge HE-2 (induced by source paper "markov processes in blockchain systems"):
  with members:
    - "a survey on consensus mechanisms and mining strategy management in blockchain networks"
    - "profitable double spending attacks"
    - "performance analysis of the raft consensus algorithm for private blockchains"
    - "a probabilistic model of the bitcoin blockchain"
    - "blockchains consensus protocols in the wild"
    - "blockchain based smart contracts a systematic mapping study"
    - "an empirical analysis of smart contracts platforms applications and design patterns"
    - "bitcoin s security model revisited"

Connected through hyperedge HE-3 (induced by source paper "an interleaving hybrid consensus protocol"):
  with members:
    - "a unifying hybrid consensus protocol"
    - "formal barriers to longest chain proof of stake protocols"
    - "cryptocurrencies without proof of work"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-4 (induced by source paper "hydra a multiple blockchain protocol for improving transaction throughput"):
  with members:
    - "enhancing bitcoin security and performance with strong consistency via collective signing"
    - "analysis of hashrate based double spending"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-5 (induced by source paper "predicting the confirmation time of bitcoin transactions"):
  with members:
    - "priority mechanism of bitcoin and its effect on transaction confirmation process"

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)