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: "johnny and jane analyzing secure email using two novice users"
  Abstract: This paper presents the results of a novel approach for conducting a laboratory user study of secure email. All prior laboratory studies involve a single novice user that communicates with an expert study coordinator to complete study tasks. In our study, we recruit a pair of novice users to come in together and attempt to exchange secure email messages. The users are instructed to send information securely, pointed at a tool to use, and given no special training or instructions other than what the tool provides. This approach more accurately simulates the grassroots adoption that is necessary for secure email to spread. We present both quantitative and qualitative results of these pairs of novice users as they experience three kinds of secure email systems: integrated (Pwm), depot (Tutanota), and an integrated-depot hybrid (Virtru).

Connected through hyperedge HE-1 (induced by source paper "messageguard retrofitting the web with user to user encryption"):
  with members:
    - "tls in the wild an internet wide analysis of tls based protocols for electronic communication"
    - "we re on the same page a usability study of secure email using pairs of novice users"
    - "private webmail 2 0 simple and easy to use secure email"
    - "why johnny still still can t encrypt evaluating the usability of a modern pgp client"

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)