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: "using smartphones as a proxy for forensic evidence contained in cloud storage services"
  Abstract: Cloud storage services such as Dropbox, Box and SugarSync have been embraced by both individuals and organizations. This creates an environment that is potentially conducive to security breaches and malicious activities. The investigation of these cloud environments presents new challenges for the digital forensics community. It is anticipated that smartphone devices will retain data from these storage services. Hence, this research presents a preliminary investigation into the residual artifacts created on an iOS and Android device that has accessed a cloud storage service. The contribution of this paper is twofold. First, it provides an initial assessment on the extent to which cloud storage data is stored on these client-side devices. This view acts as a proxy for data stored in the cloud. Secondly, it provides documentation on the artifacts that could be useful in a digital forensics investigation of cloud services.

Connected through hyperedge HE-1 (induced by source paper "a bleeding digital heart identifying residual data generation from smartphone applications interacting with medical devices"):
  with members:
    - "forensic taxonomy of popular android mhealth apps"
    - "security incident response criteria a practitioner s perspective"
    - "forensic analysis of whatsapp messenger on android smartphones"
    - "calm before the storm the challenges of cloud computing in digital forensics"

Connected through hyperedge HE-2 (induced by source paper "investigating storage as a service cloud platform pcloud as a case study"):
  with members:
    - "ubuntu one investigation detecting evidences on client machines"
    - "digital forensic investigation of cloud storage services"
    - "cloud storage forensic hubic as a case study"
    - "mobile cloud forensics an analysis of seven popular android apps"
    - "bittorrent sync first impressions and digital forensic implications"

Connected through hyperedge HE-3 (induced by source paper "cloud storage forensics analysis of data remnants on spideroak justcloud and pcloud"):
  with members:
    - "ubuntu one investigation detecting evidences on client machines"
    - "digital forensic investigation of cloud storage services"
    - "cloud storage forensic hubic as a case study"
    - "mobile cloud forensics an analysis of seven popular android apps"

Connected through hyperedge HE-4 (induced by source paper "recovering residual forensic data from smartphone interactions with cloud storage providers"):
  with members:
    - "digital forensic investigation of cloud storage services"
    - "emerging security challenges of cloud virtual infrastructure"
    - "identifying user behavior from residual data in cloud based synchronized apps"
    - "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-5 (induced by source paper "cloud storage forensic hubic as a case study"):
  with members:
    - "ubuntu one investigation detecting evidences on client machines"
    - "digital forensic investigation of cloud storage services"
    - "seclaas secure logging as a service for cloud forensics"

Connected through hyperedge HE-6 (induced by source paper "leveraging decentralization to extend the digital evidence acquisition window case study on bittorrent sync"):
  with members:
    - "digital forensic investigation of cloud storage services"
    - "bittorrent sync first impressions and digital forensic implications"
    - "bittorrent sync network investigation methodology"

Connected through hyperedge HE-7 (induced by source paper "android anti forensics modifying cyanogenmod"):
  with members:
    - "investigating information security risks of mobile device use within organizations"

Connected through hyperedge HE-8 (induced by source paper "identifying user behavior from residual data in cloud based synchronized apps"):
  with members:
    - "investigating information security risks of mobile device use within organizations"

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)