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: "lack a voip steganographic method"
  Abstract: The paper presents a new steganographic method called LACK (Lost Audio PaCKets Steganography) which is intended mainly for VoIP. The method is presented in a broader context of network steganography and of VoIP steganography in particular. The analytical results presented in the paper concern the influence of LACK's hidden data insertion procedure on the method's impact on quality of voice transmission and its resistance to steganalysis.

Connected through hyperedge HE-1 (induced by source paper "youskyde information hiding for skype video traffic"):
  with members:
    - "hidden and uncontrolled on the emergence of network steganographic threats"
    - "voip steganography and its detection a survey"
    - "on steganography in lost audio packets"

Connected through hyperedge HE-2 (induced by source paper "steganography in modern smartphones and mitigation techniques"):
  with members:
    - "steganography using the extensible messaging and presence protocol xmpp"
    - "stegtorrent a steganographic method for the p2p file sharing service"
    - "principles and overview of network steganography"
    - "voip steganography and its detection a survey"
    - "using transcoding for hidden communication in ip telephony"
    - "lost audio packets steganography the first practical evaluation"
    - "capacity of steganographic channels"

Connected through hyperedge HE-3 (induced by source paper "voip steganography and its detection a survey"):
  with members:
    - "influence of speech codecs selection on transcoding steganography"
    - "steganalysis of transcoding steganography"
    - "using transcoding for hidden communication in ip telephony"
    - "lost audio packets steganography the first practical evaluation"
    - "what are suspicious voip delays"
    - "steganography of voip streams"
    - "covert channels in sip for voip signalling"
    - "new security and control protocol for voip based on steganography and digital watermarking"

Connected through hyperedge HE-4 (induced by source paper "influence of speech codecs selection on transcoding steganography"):
  with members:
    - "speex a free codec for free speech"
    - "padsteg introducing inter protocol steganography"
    - "using transcoding for hidden communication in ip telephony"
    - "steganography of voip streams"
    - "new security and control protocol for voip based on steganography and digital watermarking"

Connected through hyperedge HE-5 (induced by source paper "using transcoding for hidden communication in ip telephony"):
  with members:
    - "lost audio packets steganography the first practical evaluation"
    - "steganography of voip streams"
    - "covert channels in sip for voip signalling"
    - "new security and control protocol for voip based on steganography and digital watermarking"

Connected through hyperedge HE-6 (induced by source paper "lost audio packets steganography the first practical evaluation"):
  with members:
    - "what are suspicious voip delays"
    - "steganography of voip streams"
    - "covert channels in sip for voip signalling"
    - "new security and control protocol for voip based on steganography and digital watermarking"

Connected through hyperedge HE-7 (induced by source paper "on steganography in lost audio packets"):
  with members:
    - "steganography of voip streams"
    - "analysis of a procedure for inserting steganographic data into voip calls"

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)