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: "games without frontiers investigating video games as a covert channel"
  Abstract: The Internet has become a critical communication infrastructure for citizens to organize protests and express dissatisfaction with their governments. This fact has not gone unnoticed, with governments clamping down on this medium via censorship, and circumvention researchers working to stay one step ahead. #R##N#In this paper, we explore a promising new avenue for covert channels: real-time strategy-video games. Video games have two key features that make them attractive cover protocols for censorship circumvention. First, due to the popularity of gaming platforms such as Steam, there are a lot of different video games, each with their own protocols and server infrastructure. Users of video-game-based censorship-circumvention tools can therefore diversify across many games, making it difficult for the censor to respond by simply blocking a single cover protocol. Second, games in the same genre have many common features and concepts. As a result, the same covert channel framework can be easily adapted to work with many different games. This means that circumvention tool developers can stay ahead of the censor by creating a diverse set of tools and by quickly adapting to blockades created by the censor. #R##N#We demonstrate the feasibility of this approach by implementing our coding scheme over two real-time strategy-games (including a very popular closed-source game). We evaluate the security of our system prototype -- Castle -- by quantifying its resilience to a censor-adversary, its similarity to real game traffic, and its ability to avoid common pitfalls in covert channel design. We use our prototype to demonstrate that our approach can provide throughput which is amenable to transfer of textual data, such at e-mail, SMS messages, and tweets, which are commonly used to organize political actions.

Connected through hyperedge HE-1 (induced by source paper "specification based protocol obfuscation"):
  with members:
    - "scramblesuit a polymorph network protocol to circumvent censorship"

Connected through hyperedge HE-2 (induced by source paper "a framework for the game theoretic analysis of censorship resistance"):
  with members:
    - "detecting internet filtering from geographic time series"
    - "on modeling the costs of censorship"
    - "ip over voice over ip for censorship circumvention"

Connected through hyperedge HE-3 (induced by source paper "systemization of pluggable transports for censorship resistance"):
  with members:
    - "a framework for the game theoretic analysis of censorship resistance"
    - "on modeling the costs of censorship"
    - "dimming the internet detecting throttling as a mechanism of censorship in iran"
    - "the velocity of censorship high fidelity detection of microblog post deletions"
    - "scramblesuit a polymorph network protocol to circumvent censorship"
    - "sweet serving the web by exploiting email tunnels"
    - "using transcoding for hidden communication in ip telephony"

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)