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: "a gamified approach to improve users memorability of fall back authentication"
  Abstract: Security questions are one of the techniques used in fall-back authentication to retrieve forgotten passwords. This paper proposes a game design which aims to improve usability of system-generated security questions. In our game design, we adapted the popular picture-based "4 Pics 1 word" mobile game. This game asks users to pick the word that relates the given pictures. We selected this game because of its use of pictures and cues, in which, psychology research has found to be important to help with memorability. The proposed game design focuses on encoding information to users' long- term memory and to aide memorability by using the follow- ing memory retrieval skills: (a) graphical cues - by using images in each challenge; (b) verbal cues - by using verbal descriptions as hints; (c) spatial cues - by keeping same or- der of pictures; (d) interactivity - engaging nature of the game through the use of persuasive technology principles.

Connected through hyperedge HE-1 (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"
    - "security strength indicator in fallback authentication nudging users for better answers in secret questions"

Connected through hyperedge HE-2 (induced by source paper "phish phinder a game design approach to enhance user confidence in mitigating phishing attacks"):
  with members:
    - "defending against phishing attacks taxonomy of methods current issues and future directions"

Connected through hyperedge HE-3 (induced by source paper "involving users in the design of a serious game for security questions education"):
  with members:
    - "changing users security behaviour towards security questions a game based learning approach"

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)