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: "presto a systematic framework for blockchain consensus protocols"
  Abstract: The rapid evolution of the blockchain community has brought together stakeholders from fundamentally different backgrounds: cryptographers, protocol designers, software developers, startup entrepreneurs, corporate executives and investors, academics of various disciplines, and end users. The result is a diverse ecosystem, presently exemplified by the development of a wide range of different blockchain protocols. This raises questions for policy and decision makers: How do different protocols compare? What are their trade-offs? Existing efforts to survey the area reveal a fragmented terminology, and the lack of a unified framework to make the different desirable properties of blockchain protocols explicit. In this paper, we work towards bridging this gap. We evaluate protocols within a five-dimensional design space with the following axes. Optimality: does the protocol achieve its main goals? Stability: are the incentives of its participating agents well-aligned? Efficiency: is its output maximal relative to its use of resources? Robustness: can it cope when its operational assumptions are invalid or perturbed? Persistence: can it recover from catastrophic events? Based on the relevant literature, we organize the properties of existing protocols in subcategories of increasing granularity. The result is a dynamic scheme -- termed the PREStO framework. Its scope is to aid the communication between stakeholders of different backgrounds, including managers and investors, and to identify research challenges and opportunities for blockchain protocols in a systematic way. We illustrate this via use cases and make a first step to understand the blockchain ecosystem through a more comprehensive lens.

Connected through hyperedge HE-1 (induced by source paper "coalition safe equilibria with virtual payoffs"):
  with members:
    - "squirrl automating attack discovery on blockchain incentive mechanisms with deep reinforcement learning"
    - "the gap game"
    - "blockchain mining games"
    - "optimal selfish mining strategies in bitcoin"
    - "majority is not enough bitcoin mining is vulnerable"
    - "on bitcoin and red balloons"
    - "an almost surely terminating polynomial protocol for asynchronous byzantine agreement with optimal resilience"

Connected through hyperedge HE-2 (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"

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)