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: "forensic analysis of whatsapp messenger on android smartphones"
  Abstract: We present the forensic analysis of the artifacts left on Android devices by WhatsApp Messenger, the client of the WhatsApp instant messaging system. We provide a complete description of all the artifacts generated by WhatsApp Messenger, we discuss the decoding and the interpretation of each one of them, and we show how they can be correlated together to infer various types of information that cannot be obtained by considering each one of them in isolation.By using the results discussed in this paper, an analyst will be able to reconstruct the list of contacts and the chronology of the messages that have been exchanged by users. Furthermore, thanks to the correlation of multiple artifacts, (s)he will be able to infer information like when a specific contact has been added, to recover deleted contacts and their time of deletion, to determine which messages have been deleted, when these messages have been exchanged, and the users that exchanged them.

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"
    - "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-2 (induced by source paper "wsemail a retrospective on a system for secure internet messaging based on web services"):
  with members:
    - "cryptocat adopting accessibility and ease of use as security properties"
    - "tulafale a security tool for web services"

Connected through hyperedge HE-3 (induced by source paper "evihunter identifying digital evidence in the permanent storage of android devices via static analysis"):
  with members:
    - "horndroid practical and sound static analysis of android applications by smt solving"

Connected through hyperedge HE-4 (induced by source paper "forensics analysis of android mobile voip apps"):
  with members:
    - "windows instant messaging app forensics facebook and skype as case studies"
    - "on the feasibility of attribute based encryption on smartphone devices"
    - "a forensically sound adversary model for mobile devices"
    - "forensic taxonomy of popular android mhealth apps"
    - "mobile cloud forensics an analysis of seven popular android apps"
    - "conceptual evidence collection and analysis methodology for android devices"
    - "privacy risks in mobile dating apps"
    - "can t you hear me knocking identification of user actions on android apps via traffic analysis"

Connected through hyperedge HE-5 (induced by source paper "forensic investigation of social media and instant messaging services in firefox os facebook twitter google telegram openwapp and line as case studies"):
  with members:
    - "windows instant messaging app forensics facebook and skype as case studies"

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)