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: "a semantic framework for the security analysis of ethereum smart contracts"
  Abstract: Smart contracts are programs running on cryptocurrency (e.g., Ethereum) blockchains, whose popularity stem from the possibility to perform financial transactions, such as payments and auctions, in a distributed environment without need for any trusted third party. Given their financial nature, bugs or vulnerabilities in these programs may lead to catastrophic consequences, as witnessed by recent attacks. Unfortunately, programming smart contracts is a delicate task that requires strong expertise: Ethereum smart contracts are written in Solidity, a dedicated language resembling JavaScript, and shipped over the blockchain in the EVM bytecode format. In order to rigorously verify the security of smart contracts, it is of paramount importance to formalize their semantics as well as the security properties of interest, in particular at the level of the bytecode being executed.

Connected through hyperedge HE-1 (induced by source paper "ae gis shielding vulnerable smart contracts against attacks"):
  with members:
    - "slither a static analysis framework for smart contracts"
    - "soliditycheck quickly detecting smart contract problems through regular expressions"
    - "harvey a greybox fuzzer for smart contracts"
    - "exploiting the laws of order in smart contracts"
    - "finding the greedy prodigal and suicidal contracts at scale"
    - "contractfuzzer fuzzing smart contracts for vulnerability detection"
    - "towards safer smart contracts a sequence learning approach to detecting security threats"
    - "towards safer smart contracts a sequence learning approach to detecting vulnerabilities"

Connected through hyperedge HE-2 (induced by source paper "formalising and verifying smart contracts with solidifier a bounded model checker for solidity"):
  with members:
    - "smt friendly formalization of the solidity memory model"
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "solc verify a modular verifier for solidity smart contracts"
    - "hyperledger fabric a distributed operating system for permissioned blockchains"
    - "formal specification and verification of smart contracts for azure blockchain"
    - "securify practical security analysis of smart contracts"

Connected through hyperedge HE-3 (induced by source paper "smt friendly formalization of the solidity memory model"):
  with members:
    - "a survey on ethereum systems security vulnerabilities attacks and defenses"
    - "a minimal core calculus for solidity contracts"
    - "formal specification and verification of smart contracts for azure blockchain"
    - "executable operational semantics of solidity"

Connected through hyperedge HE-4 (induced by source paper "albert an intermediate smart contract language for the tezos blockchain"):
  with members:
    - "mi cho coq a framework for certifying tezos smart contracts"
    - "scilla a smart contract intermediate level language"

Connected through hyperedge HE-5 (induced by source paper "adf ga data flow criterion based test case generation for ethereum smart contracts"):
  with members:
    - "contractfuzzer fuzzing smart contracts for vulnerability detection"
    - "securify practical security analysis of smart contracts"

Connected through hyperedge HE-6 (induced by source paper "formal specification of a security framework for smart contracts"):
  with members:
    - "deductive proof of ethereum smart contracts using why3"

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 "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"

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)