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: "bitcoin transaction malleability and mtgox"
  Abstract: In Bitcoin, transaction malleability describes the fact that the signatures that prove the ownership of bitcoins being transferred in a transaction do not provide any integrity guarantee for the signatures themselves. This allows an attacker to mount a malleability attack in which it intercepts, modifies, and rebroadcasts a transaction, causing the transaction issuer to believe that the original transaction was not confirmed. In February 2014 MtGox, once the largest Bitcoin exchange, closed and filed for bankruptcy claiming that attackers used malleability attacks to drain its accounts. In this work we use traces of the Bitcoin network for over a year preceding the filing to show that, while the problem is real, there was no widespread use of malleability attacks before the closure of MtGox.

Connected through hyperedge HE-1 (induced by source paper "bandwidth efficient transaction relay for bitcoin"):
  with members:
    - "dandelion lightweight cryptocurrency networking with formal anonymity guarantees"
    - "txprobe discovering bitcoin s network topology using orphan transactions"
    - "bitcoin ng a scalable blockchain protocol"
    - "multi party set reconciliation using characteristic polynomials"
    - "deanonymisation of clients in bitcoin p2p network"
    - "majority is not enough bitcoin mining is vulnerable"
    - "simple multi party set reconciliation"
    - "hosting byzantine fault tolerant services on a chord ring"

Connected through hyperedge HE-2 (induced by source paper "a survey on security and privacy issues of bitcoin"):
  with members:
    - "concurrency and privacy with payment channel networks"
    - "dandelion redesigning the bitcoin network for anonymity"
    - "consensus in the age of blockchains"
    - "when the cookie meets the blockchain privacy risks of web payments via cryptocurrencies"
    - "be selfish and avoid dilemmas fork after withholding faw attacks on bitcoin"
    - "socially optimal mining pools"
    - "the balance attack against proof of work blockchains the r3 testbed as an example"
    - "hijacking bitcoin routing attacks on cryptocurrencies"

Connected through hyperedge HE-3 (induced by source paper "an evaluation of the security of the bitcoin peer to peer network"):
  with members:
    - "off path hacking the illusion of challenge response authentication"
    - "off path attacking the web"

Connected through hyperedge HE-4 (induced by source paper "zero collateral lotteries in bitcoin and ethereum"):
  with members:
    - "decentralized prediction market without arbiters"

Connected through hyperedge HE-5 (induced by source paper "bitcoin meets strong consistency"):
  with members:
    - "analysis of hashrate based double spending"
    - "majority is not enough bitcoin mining is vulnerable"
    - "on bitcoin and red balloons"
    - "analysis of bitcoin pooled mining reward systems"

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)