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: "horndroid practical and sound static analysis of android applications by smt solving"
  Abstract: We present HornDroid, a new tool for the static analysis of information flow properties in Android applications. The core idea underlying HornDroid is to use Horn clauses for soundly abstracting the semantics of Android applications and to express security properties as a set of proof obligations that are automatically discharged by an off-the-shelf SMT solver. This approach makes it possible to fine-tune the analysis in order to achieve a high degree of precision while still using off-the-shelf verification tools, thereby leveraging the recent advances in this field. As a matter of fact, HornDroid outperforms state-of-the-art Android static analysis tools on benchmarks proposed by the community. Moreover, HornDroid is the first static analysis tool for Android to come with a formal proof of soundness, which covers the core of the analysis technique: besides yielding correctness assurances, this proof allowed us to identify some critical corner-cases that affect the soundness guarantees provided by some of the previous static analysis tools for Android.

Connected through hyperedge HE-1 (induced by source paper "are free android app security analysis tools effective in detecting known vulnerabilities"):
  with members:
    - "do android taint analysis tools keep their promises"
    - "ghera a repository of android app vulnerability benchmarks"
    - "an application package configuration approach to mitigating android ssl vulnerabilities"

Connected through hyperedge HE-2 (induced by source paper "benchpress analyzing android app vulnerability benchmark suites"):
  with members:
    - "are free android app security analysis tools effective in detecting known vulnerabilities"
    - "do android taint analysis tools keep their promises"
    - "ghera a repository of android app vulnerability benchmarks"
    - "beebs open benchmarks for energy measurements on embedded platforms"

Connected through hyperedge HE-3 (induced by source paper "discovering flaws in security focused static analysis tools for android using systematic mutation"):
  with members:
    - "crashscope a practical tool for automated testing of android applications"
    - "enabling mutation testing for android apps"
    - "automatically discovering reporting and reproducing android application crashes"
    - "adsplit separating smartphone advertising from applications"
    - "quire lightweight provenance for smart phone operating systems"

Connected through hyperedge HE-4 (induced by source paper "open source android vulnerability detection tools a survey"):
  with members:
    - "leaksemantic identifying abnormal sensitive network transmissions in mobile applications"
    - "i know what leaked in your pocket uncovering privacy leaks on android apps with static taint analysis"

Connected through hyperedge HE-5 (induced by source paper "dexlego reassembleable bytecode extraction for aiding static analysis"):
  with members:
    - "trustshadow secure execution of unmodified applications with arm trustzone"

Connected through hyperedge HE-6 (induced by source paper "evihunter identifying digital evidence in the permanent storage of android devices via static analysis"):
  with members:
    - "forensic analysis of whatsapp messenger on android smartphones"

Connected through hyperedge HE-7 (induced by source paper "a sound flow sensitive heap abstraction for the static analysis of android applications"):
  with members:
    - "heap abstractions for static analysis"

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)