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: "rethinking blockchain security position paper"
  Abstract: Blockchain technology has become almost as famous for incidents involving security breaches as for its innovative potential. We shed light on the prevalence and nature of these incidents through a database structured using the STIX format. Apart from OPSEC-related incidents, we find that the nature of many incidents is specific to blockchain technology. Two categories stand out: smart contracts, and techno-economic protocol incentives. For smart contracts, we propose to use recent advances in software testing to find flaws before deployment. For protocols, we propose the PRESTO framework that allows us to compare different protocols within a five-dimensional framework.

Connected through hyperedge HE-1 (induced by source paper "a survey on ethereum systems security vulnerabilities attacks and defenses"):
  with members:
    - "security and privacy on blockchain"
    - "exploring the attack surface of blockchain a systematic overview"
    - "a survey on consensus mechanisms and mining strategy management in blockchain networks"
    - "metrics towards measuring cyber agility"
    - "selfish mining in ethereum"
    - "a survey of distributed consensus protocols for blockchain networks"
    - "finding the greedy prodigal and suicidal contracts at scale"
    - "ethir a framework for high level analysis of ethereum bytecode"

Connected through hyperedge HE-2 (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-3 (induced by source paper "weighted voting on the blockchain improving consensus in proof of stake protocols"):
  with members:
    - "incentives in ethereum s hybrid casper protocol"
    - "reward sharing schemes for stake pools"
    - "hyperledger fabric a distributed operating system for permissioned blockchains"
    - "betting on blockchain consensus with fantomette"
    - "consensus in the age of blockchains"
    - "multiplicative weights update with constant step size in congestion games convergence limit cycles and chaos"
    - "casper the friendly finality gadget"
    - "untangling blockchain a data processing view of blockchain systems"

Connected through hyperedge HE-4 (induced by source paper "truffle tests for free replaying ethereum smart contracts for transparency"):
  with members:
    - "probabilistic smart contracts secure randomness on the blockchain"
    - "finding the greedy prodigal and suicidal contracts at scale"
    - "detecting token systems on ethereum"
    - "contractfuzzer fuzzing smart contracts for vulnerability detection"
    - "securify practical security analysis of smart contracts"
    - "new kids on the block an analysis of modern blockchains"

Connected through hyperedge HE-5 (induced by source paper "smartotps an air gapped 2 factor authentication for smart contract wallets"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "an air gapped 2 factor authentication for smart contract wallets"
    - "a first look at the usability of bitcoin key management"

Connected through hyperedge HE-6 (induced by source paper "mutation testing for ethereum smart contract"):
  with members:
    - "finding the greedy prodigal and suicidal contracts at scale"
    - "contractfuzzer fuzzing smart contracts for vulnerability detection"
    - "an empirical analysis of smart contracts platforms applications and design patterns"

Connected through hyperedge HE-7 (induced by source paper "an air gapped 2 factor authentication for smart contract wallets"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "a first look at the usability of bitcoin key management"

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)