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: "just enough security reducing proof of work ecological footprint"
  Abstract: Proof-of-work (PoW) mechanisms secure about 80% of the $250B cryptocurrency market. PoW requires system participants to expend computational resources, and protects the system from attackers who cannot expend resources at an equivalent rate. These systems operate in the permissionless setting and compensate their users with cryptocurrency, having a monetary value. As cryptocurrency prices sore so do the invested resources, and Bitcoin expenditures alone are 0.24% of the global electricity consumption. Arguably, this is superfluous, and lowering the ecological footprint justifies settling for a lower attack threshold. #R##N#We present novel protocols that allow the system designer to accurately trade off security for expenditure reduction. To the best of our knowledge, this is the first work to do so without adding qualitatively stronger model assumptions. Moreover, our protocols reduce PoW resource expenditure significantly, but with only limited security degradation. #R##N#To analyze these protocols We refine the common blockchain model to take into account the cryptocurrency value in real terms, expenditure, and security metrics, distinguishing common revenue-seeking attacks from sabotage. Our analysis of game-theoretic and economical properties of the protocols can be used to tune blockchain security to its required level and limit its ecological damage.

Connected through hyperedge HE-1 (induced by source paper "bdos blockchain denial of service"):
  with members:
    - "competing semi selfish miners in bitcoin"
    - "bitcoin vs bitcoin cash coexistence or downfall of bitcoin cash"
    - "sok transparent dishonesty front running attacks on blockchain"
    - "selfish mining in ethereum"
    - "mind the mining"
    - "cryptocurrency egalitarianism a quantitative approach"
    - "flash boys 2 0 frontrunning transaction reordering and consensus instability in decentralized exchanges"
    - "a deep dive into blockchain selfish mining"

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)