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: "chainspace a sharded smart contracts platform"
  Abstract: Chainspace is a decentralized infrastructure, known as a distributed ledger, that supports user defined smart contracts and executes user-supplied transactions on their objects. The correct execution of smart contract transactions is verifiable by all. The system is scalable, by sharding state and the execution of transactions, and using S-BAC, a distributed commit protocol, to guarantee consistency. Chainspace is secure against subsets of nodes trying to compromise its integrity or availability properties through Byzantine Fault Tolerance (BFT), and extremely high-auditability, non-repudiation and `blockchain' techniques. Even when BFT fails, auditing mechanisms are in place to trace malicious participants. We present the design, rationale, and details of Chainspace; we argue through evaluating an implementation of the system about its scaling and other features; we illustrate a number of privacy-friendly smart contracts for smart metering, polling and banking and measure their performance.

Connected through hyperedge HE-1 (induced by source paper "surface a practical blockchain consensus algorithm for real world networks"):
  with members:
    - "rationality is self defeating in permissionless systems"
    - "dfinity technology overview series consensus system"
    - "hotstuff bft consensus in the lens of blockchain"
    - "deconstructing the blockchain to approach physical limits"
    - "scaling nakamoto consensus to thousands of transactions per second"
    - "transaction propagation on permissionless blockchains incentive and routing mechanisms"
    - "implicit consensus blockchain with unbounded throughput"
    - "casper the friendly finality gadget"

Connected through hyperedge HE-2 (induced by source paper "verifiable and auditable digital interchange framework"):
  with members:
    - "hyperledger fabric a distributed operating system for permissioned blockchains"
    - "sprites and state channels payment networks that go faster than lightning"
    - "performance characterization of a commercial video streaming service"
    - "bitcoin ng a scalable blockchain protocol"
    - "centrally banked cryptocurrencies"

Connected through hyperedge HE-3 (induced by source paper "fides managing data on untrusted infrastructure"):
  with members:
    - "parblockchain leveraging transaction parallelism in permissioned blockchain systems"
    - "hyperledger fabric a distributed operating system for permissioned blockchains"
    - "enhancing bitcoin security and performance with strong consistency via collective signing"
    - "keeping authorities honest or bust with decentralized witness cosigning"

Connected through hyperedge HE-4 (induced by source paper "ostraka secure blockchain scaling by node sharding"):
  with members:
    - "decentralization in bitcoin and ethereum networks"
    - "hotstuff bft consensus in the lens of blockchain"
    - "split scale scaling bitcoin by partitioning the utxo space"
    - "dietcoin shortcutting the bitcoin verification process for your smartphone"
    - "adding concurrency to smart contracts"
    - "casper the friendly finality gadget"
    - "enhancing bitcoin security and performance with strong consistency via collective signing"
    - "service oriented sharding with aspen"

Connected through hyperedge HE-5 (induced by source paper "hyperservice interoperability and programmability across heterogeneous blockchains"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "concurrency and privacy with payment channel networks"
    - "keystone an open framework for architecting tees"
    - "atomic cross chain swaps"
    - "saql a stream based query system for real time abnormal system behavior detection"
    - "aiql enabling efficient attack investigation from system monitoring data"
    - "a concurrent perspective on smart contracts"
    - "enhancing bitcoin security and performance with strong consistency via collective signing"

Connected through hyperedge HE-6 (induced by source paper "dipetrans a framework for distributed parallel execution of transactions of blocks in blockchain"):
  with members:
    - "achieving greater concurrency in execution of smart contracts using object semantics"
    - "security and privacy on blockchain"
    - "an empirical study of speculative concurrency in ethereum smart contracts"
    - "a true concurrent model of smart contracts executions"
    - "an efficient framework for optimistic concurrent execution of smart contracts"
    - "adding concurrency to smart contracts"
    - "the miner s dilemma"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-7 (induced by source paper "empirically analyzing ethereum s gas mechanism"):
  with members:
    - "an empirical study of speculative concurrency in ethereum smart contracts"
    - "decentralization in bitcoin and ethereum networks"
    - "an efficient framework for optimistic concurrent execution of smart contracts"
    - "adding concurrency to smart contracts"
    - "an empirical analysis of smart contracts platforms applications and design patterns"
    - "new kids on the block an analysis of modern blockchains"
    - "optimal selfish mining strategies in bitcoin"
    - "bitcoin transaction graph analysis"

Connected through hyperedge HE-8 (induced by source paper "broken metre attacking resource metering in evm"):
  with members:
    - "gastap a gas analyzer for smart contracts"
    - "contractfuzzer fuzzing smart contracts for vulnerability detection"
    - "towards safer smart contracts a survey of languages and verification methods"
    - "vandal a scalable security analysis framework for smart contracts"
    - "securify practical security analysis of smart contracts"
    - "an adaptive gas cost mechanism for ethereum to defend against under priced dos attacks"
    - "under optimized smart contracts devour your money"
    - "majority is not enough bitcoin mining is vulnerable"

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)