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: "concurrency and privacy with payment channel networks"
  Abstract: Permissionless blockchains protocols such as Bitcoin are inherently limited in transaction throughput and latency. Current efforts to address this key issue focus on off-chain payment channels that can be combined in a Payment-Channel Network (PCN) to enable an unlimited number of payments without requiring to access the blockchain other than to register the initial and final capacity of each channel. While this approach paves the way for low latency and high throughput of payments, its deployment in practice raises several privacy concerns as well as technical challenges related to the inherently concurrent nature of payments, such as race conditions and deadlocks, that have been understudied so far. In this work, we lay the foundations for privacy and concurrency in PCNs, presenting a formal definition in the Universal Composability framework as well as practical and provably secure solutions. In particular, we present Fulgor and Rayo. Fulgor is the first payment protocol for PCNs that provides provable privacy guarantees for PCNs and is fully compatible with the Bitcoin scripting system. However, Fulgor is a blocking protocol and therefore prone to deadlocks of concurrent payments as in currently available PCNs. Instead, Rayo is the first protocol for PCNs that enforces non-blocking progress (i.e., at least one of the concurrent payments terminates). We show through a new impossibility result that non-blocking progress necessarily comes at the cost of weaker privacy. At the core of Fulgor and Rayo is Multi-Hop HTLC, a new smart contract, compatible with the Bitcoin scripting system, that provides conditional payments while reducing running time and communication overhead with respect to previous approaches.

Connected through hyperedge HE-1 (induced by source paper "hushrelay a privacy preserving efficient and scalable routing algorithm for off chain payments"):
  with members:
    - "topological analysis of bitcoin s lightning network"
    - "ant routing algorithm for the lightning network"
    - "routing cryptocurrency with the spider network"
    - "consensus in the age of blockchains"
    - "towards a concurrent and distributed route selection for payment channel networks"
    - "casper the friendly finality gadget"
    - "settling payments fast and private efficient decentralized routing for path based transactions"
    - "voute virtual overlays using tree embeddings"

Connected through hyperedge HE-2 (induced by source paper "effective scaling of blockchain beyond consensus innovations and moore s law"):
  with members:
    - "scalable byzantine consensus via hardware assisted secret sharing"
    - "blockchain goes green an analysis of blockchain on low power nodes"
    - "an energy efficient reconfigurable dtls cryptographic engine for securing internet of things applications"
    - "morph an adaptive framework for efficient and byzantine fault tolerant sdn control plane"
    - "towards scaling blockchain systems via sharding"
    - "a scale out blockchain for value transfer with spontaneous sharding"
    - "scaling nakamoto consensus to thousands of transactions per second"
    - "blockbench a framework for analyzing private blockchains"

Connected through hyperedge HE-3 (induced by source paper "congestion attacks in payment channel networks"):
  with members:
    - "privacy utility tradeoffs in routing cryptocurrency over payment channel networks"
    - "hijacking routes in payment channel networks a predictability tradeoff"
    - "topological analysis of bitcoin s lightning network"
    - "discharged payment channels quantifying the lightning network s resilience to topology based attacks"
    - "towards secure and efficient payment channels"
    - "sprites and state channels payment networks that go faster than lightning"

Connected through hyperedge HE-4 (induced by source paper "fail safe watchtowers and short lived assertions for payment channels"):
  with members:
    - "towards secure and efficient payment channels"
    - "teechain a secure asynchronous blockchain payment network"
    - "bitcoin ng a scalable blockchain protocol"

Connected through hyperedge HE-5 (induced by source paper "balance transfers and bailouts in credit networks using blockchains"):
  with members:
    - "settling payments fast and private efficient decentralized routing for path based transactions"
    - "voute virtual overlays using tree embeddings"

Connected through hyperedge HE-6 (induced by source paper "hyperservice interoperability and programmability across heterogeneous blockchains"):
  with members:
    - "ekiden a platform for confidentiality preserving trustworthy and performant smart contracts"
    - "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"
    - "chainspace a sharded smart contracts platform"
    - "a concurrent perspective on smart contracts"
    - "enhancing bitcoin security and performance with strong consistency via collective signing"

Connected through hyperedge HE-7 (induced by source paper "privacy utility tradeoffs in routing cryptocurrency over payment channel networks"):
  with members:
    - "celer network bring internet scale to every blockchain"
    - "routing cryptocurrency with the spider network"
    - "ohie blockchain scaling made simple"
    - "high throughput cryptocurrency routing in payment channel networks"
    - "dandelion redesigning the bitcoin network for anonymity"
    - "settling payments fast and private efficient decentralized routing for path based transactions"
    - "deanonymisation of clients in bitcoin p2p network"
    - "extremal mechanisms for local differential privacy"

Connected through hyperedge HE-8 (induced by source paper "microcash practical concurrent processing of micropayments"):
  with members:
    - "sprites and state channels payment networks that go faster than lightning"
    - "optimal selfish mining strategies in bitcoin"

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)