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: "security strength indicator in fallback authentication nudging users for better answers in secret questions"
  Abstract: In this paper, we describe ongoing work that focuses on improving the strength of the answers to security questions. The ultimate goal of the proposed research is to evaluate the possibility of nudging users towards strong answers for ubiquitous security questions. In this research we are proposing a user interface design for fallback authentication to encourage users to design stronger answers. The proposed design involves visual feedback to the user based on mnemonics which attempts to give visual feedback to the user on the strength of the answer provided and guide the user to creatively design a stronger answer.

Connected through hyperedge HE-1 (induced by source paper "changing users security behaviour towards security questions a game based learning approach"):
  with members:
    - "data driven authentication on the effectiveness of user behaviour modelling with mobile device sensors"
    - "naturally rehearsing passwords"

Connected through hyperedge HE-2 (induced by source paper "a gamified approach to improve users memorability of fall back authentication"):
  with members:
    - "data driven authentication on the effectiveness of user behaviour modelling with mobile device sensors"
    - "naturally rehearsing passwords"

Connected through hyperedge HE-3 (induced by source paper "a model for enhancing human behaviour with security questions a theoretical perspective"):
  with members:
    - "changing users security behaviour towards security questions a game based learning approach"
    - "a gamified approach to improve users memorability of fall back authentication"

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)