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: "emerging security challenges of cloud virtual infrastructure"
  Abstract: The cloud computing model is rapidly transforming the IT landscape. Cloud computing is a new computing paradigm that delivers computing resources as a set of reliable and scalable internet-based services allowing customers to remotely run and manage these services. Infrastructure-as-a-service (IaaS) is one of the popular cloud computing services. IaaS allows customers to increase their computing resources on the fly without investing in new hardware. IaaS adapts virtualization to enable on-demand access to a pool of virtual computing resources. Although there are great benefits to be gained from cloud computing, cloud computing also enables new categories of threats to be introduced. These threats are a result of the cloud virtual infrastructure complexity created by the adoption of the virtualization technology. #R##N#Breaching the security of any component in the cloud virtual infrastructure significantly impacts on the security of other components and consequently affects the overall system security. This paper explores the security problem of the cloud platform virtual infrastructure identifying the existing security threats and the complexities of this virtual infrastructure. The paper also discusses the existing security approaches to secure the cloud virtual infrastructure and their drawbacks. Finally, we propose and explore some key research challenges of implementing new virtualization-aware security solutions that can provide the pre-emptive protection for complex and ever- dynamic cloud virtual infrastructure.

Connected through hyperedge HE-1 (induced by source paper "recovering residual forensic data from smartphone interactions with cloud storage providers"):
  with members:
    - "digital forensic investigation of cloud storage services"
    - "identifying user behavior from residual data in cloud based synchronized apps"
    - "using smartphones as a proxy for forensic evidence contained in cloud storage services"
    - "cloud security challenges investigating policies standards and guidelines in a fortune 500 organization"
    - "calm before the storm the challenges of cloud computing in digital forensics"

Connected through hyperedge HE-2 (induced by source paper "cloud security challenges investigating policies standards and guidelines in a fortune 500 organization"):
  with members:
    - "using smartphones as a proxy for forensic evidence contained in cloud storage services"
    - "calm before the storm the challenges of cloud computing in digital forensics"

Connected through hyperedge HE-3 (induced by source paper "cloud computing security in business information systems"):
  with members:
    - "an overview of the security concerns in enterprise cloud computing"

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)