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 geometric protocol for cryptography with cards"
  Abstract: In the generalized Russian cards problem, the three players Alice, Bob and Cath draw a,b and c cards, respectively, from a deck of a+b+c cards. Players only know their own cards and what the deck of cards is. Alice and Bob are then required to communicate their hand of cards to each other by way of public messages. The communication is said to be safe if Cath does not learn the ownership of any specific card; in this paper we consider a strengthened notion of safety introduced by Swanson and Stinson which we call k-safety. #R##N#An elegant solution by Atkinson views the cards as points in a finite projective plane. We propose a general solution in the spirit of Atkinson's, although based on finite vector spaces rather than projective planes, and call it the `geometric protocol'. Given arbitrary c,k>0, this protocol gives an informative and k-safe solution to the generalized Russian cards problem for infinitely many values of (a,b,c) with b=O(ac). This improves on the collection of parameters for which solutions are known. In particular, it is the first solution which guarantees $k$-safety when Cath has more than one card.

Connected through hyperedge HE-1 (induced by source paper "perfectly secure data aggregation via shifted projections"):
  with members:
    - "a case study in almost perfect security for unconditionally secure communication"
    - "almost perfect security for the russian cards problem"
    - "additional constructions to solve the generalized russian cards problem using combinatorial designs"
    - "a colouring protocol for the generalized russian cards problem"

Connected through hyperedge HE-2 (induced by source paper "a case study in almost perfect security for unconditionally secure communication"):
  with members:
    - "perfectly secure data aggregation via shifted projections"
    - "additional constructions to solve the generalized russian cards problem using combinatorial designs"
    - "a colouring protocol for the generalized russian cards problem"

Connected through hyperedge HE-3 (induced by source paper "almost perfect security for the russian cards problem"):
  with members:
    - "additional constructions to solve the generalized russian cards problem using combinatorial designs"
    - "a colouring protocol for the generalized russian cards problem"

Connected through hyperedge HE-4 (induced by source paper "additional constructions to solve the generalized russian cards problem using combinatorial designs"):
  with members:
    - "a colouring protocol for the generalized russian cards problem"
    - "lower bound for the communication complexity of the russian cards problem"

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)