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: "teechan payment channels using trusted execution environments"
  Abstract: Blockchain protocols are inherently limited in transaction throughput and latency. Recent efforts to address performance and scale blockchains have focused on off-chain payment channels. While such channels can achieve low latency and high throughput, deploying them securely on top of the Bitcoin blockchain has been difficult, partly because building a secure implementation requires changes to the underlying protocol and the ecosystem. #R##N#We present Teechan, a full-duplex payment channel framework that exploits trusted execution environments. Teechan can be deployed securely on the existing Bitcoin blockchain without having to modify the protocol. It: (i) achieves a higher transaction throughput and lower transaction latency than prior solutions; (ii) enables unlimited full-duplex payments as long as the balance does not exceed the channel's credit; (iii) requires only a single message to be sent per payment in any direction; and (iv) places at most two transactions on the blockchain under any execution scenario. #R##N#We have built and deployed the Teechan framework using Intel SGX on the Bitcoin network. Our experiments show that, not counting network latencies, Teechan can achieve 2,480 transactions per second on a single channel, with sub-millisecond latencies.

Connected through hyperedge HE-1 (induced by source paper "keystone an open framework for architecting tees"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "zombieload cross privilege boundary data sampling"
    - "practical verifiable in network filtering for ddos defense"
    - "sanctorum a lightweight security monitor for secure enclaves"
    - "spectre attacks exploiting speculative execution"
    - "besfs mechanized proof of an iago safe filesystem for enclaves"
    - "privado practical and secure dnn inference"
    - "mi6 secure enclaves in a speculative out of order processor"

Connected through hyperedge HE-2 (induced by source paper "iperftz understanding network bottlenecks for trustzone based trusted applications"):
  with members:
    - "using trusted execution environments for secure stream processing of medical data"
    - "streambox tz secure stream analytics at the edge with trustzone"
    - "on the performance of arm trustzone"
    - "developing secure services for iot with op tee a first look at performance and usability"
    - "spectre attacks exploiting speculative execution"
    - "challenges and opportunities in edge computing"
    - "open tee an open virtual trusted execution environment"

Connected through hyperedge HE-3 (induced by source paper "trustee full privacy preserving vickrey auction on top of ethereum"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "airtnt fair exchange payment for outsourced secure enclave computations"
    - "blockchain and trusted computing problems pitfalls and a solution for hyperledger fabric"
    - "malware guard extension using sgx to conceal cache attacks"
    - "inferring fine grained control flow inside sgx enclaves with branch shadowing"
    - "proof of luck an efficient blockchain consensus protocol"
    - "ipfs content addressed versioned p2p file system"

Connected through hyperedge HE-4 (induced by source paper "a tale of two trees one writes and other reads optimized oblivious accesses to large scale blockchains"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "securing the storage data path with sgx enclaves"
    - "concuroram high throughput stateless parallel multi client oram"
    - "software grand exposure sgx cache attacks are practical"
    - "inferring fine grained control flow inside sgx enclaves with branch shadowing"

Connected through hyperedge HE-5 (induced by source paper "discharged payment channels quantifying the lightning network s resilience to topology based attacks"):
  with members:
    - "topological analysis of bitcoin s lightning network"
    - "towards secure and efficient payment channels"
    - "decentralization in bitcoin and ethereum networks"
    - "towards a concurrent and distributed route selection for payment channel networks"
    - "settling payments fast and private efficient decentralized routing for path based transactions"

Connected through hyperedge HE-6 (induced by source paper "privacy preserving p2p energy market on the blockchain"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "encointer an ecological egalitarian and private cryptocurrency and self sovereign identity system"
    - "providing privacy safety and security in iot based transactive energy systems using distributed ledgers"

Connected through hyperedge HE-7 (induced by source paper "concurrency and privacy with payment channel networks"):
  with members:
    - "mind your credit assessing the health of the ripple credit network"

Connected through hyperedge HE-8 (induced by source paper "pubsub sgx exploiting trusted execution environments for privacy preserving publish subscribe systems"):
  with members:
    - "securestreams a reactive middleware framework for secure data stream processing"
    - "x search revisiting private web search using intel sgx"
    - "secure and privacy aware data dissemination for cloud based applications"
    - "secure content based routing using intel software guard extensions"

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)