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: "improved robust dwt watermarking in ycbcr color space"
  Abstract: Digital watermarking is an effective way to protect copyright. In this paper, a robust watermarking algorithm based on wavelet transformation is proposed which can confirm the copyright without original image. The wavelet transformation technique is effective in image analyzing and processing. Thus the color-image watermark algorithm based on discrete wavelet transformation (DWT) begins to draw an increasing attention. In the proposed approach, the watermark Encrypt by Arnold transform and the host image is converted into the YCbCr color space. Then its Y channel decomposed into wavelet coefficients and the selected approximation coefficients are quantized and then their least significant bit of the quantized coefficients is replaced by the Encrypted watermark using LSB insertion technique. The experimental results show that watermark embedded by this algorithm is of better robustness and extra imperceptibility and robustness against wavelet compression compared to the traditional embedding methods in RGB color space.

Connected through hyperedge HE-1 (induced by source paper "a dct and svd based watermarking technique to identify tag"):
  with members:
    - "improved watermarking scheme using discrete cosine transform and schur decomposition"
    - "a dwt dct and svd based watermarking technique to protect the image piracy"
    - "digital watermarking for image authenticationbased on combined dct dwt and svd transformation"
    - "an approach of digital image copyright protection by using watermarking technology"
    - "perceptual copyright protection using multiresolution wavelet based watermarking and fuzzy logic"

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)