human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "heb hybrid expenditure blockchain"):
  Abstract: The study of Proof of Work (PoW) has culminated with the introduction of cryptocurrency blockchains like Bitcoin. These protocols require their operators, called miners, to expend computational resources and they reward them with minted cryptocurrency tokens. The system is secure from attackers who cannot expend resources at a rate equivalent to that of all benign miners. But the resource requirement is arbitrary - the product of the number of minted tokens and their real value. We present Hybrid Expenditure Blockchain (HEB), a novel cryptocurrency PoW protocol that allows its designer to tune external expenditure. To the best of our knowledge, this is the first tunable PoW protocol. Despite the reduced resource expenditure, it maintains the security guarantees of pure PoW protocols against rational attacks. HEB has practical implications, as global power expenditure on PoW blockchains exceeds that of a medium-sized country. Applying HEB in operational PoW systems can significantly reduce their ecological footprint.

Includes members:
  Member "mind the mining":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "double spend counterattacks threat of retaliation in proof of work systems")
  Member "squirrl automating attack discovery on blockchain incentive mechanisms with deep reinforcement learning":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "on the convergence of artificial intelligence and distributed ledger technology a scoping review and future research agenda")
  Member "an axiomatic approach to block rewards":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "sok tools for game theoretic models of security for cryptocurrencies")
  Member "sbft a scalable and decentralized trust infrastructure":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "expected linear round synchronization the missing link for linear byzantine smr")
  Member "sbft a scalable decentralized trust infrastructure for blockchains":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "sharper sharding permissioned blockchains over network clusters")
  Member "a survey on security and privacy issues of bitcoin":
    also connected through other hyperedges:
      - Hyperedge HE-6 (induced by source paper "on the feasibility of sybil attacks in shard based permissionless blockchains")
  Member "the gap game":
    also connected through other hyperedges:
      - Hyperedge HE-7 (induced by source paper "incentive analysis of bitcoin ng revisited")
  Member "bitcoin a natural oligopoly":
    also connected through other hyperedges:
      - Hyperedge HE-8 (induced by source paper "double spend counterattacks threat of retaliation in proof of work systems")

Question: Please tell me which class the source paper 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)