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: "lost audio packets steganography the first practical evaluation"
  Abstract: This paper presents first experimental results for an IP telephony-based steganographic method called LACK (Lost Audio PaCKets steganography). This method utilizes the fact that in typical multimedia communication protocols like RTP (Real-Time Transport Protocol), excessively delayed packets are not used for the reconstruction of transmitted data at the receiver, i.e. these packets are considered useless and discarded. The results presented in this paper were obtained basing on a functional LACK prototype and show the method's impact on the quality of voice transmission. Achievable steganographic bandwidth for the different IP telephony codecs is also calculated.

Connected through hyperedge HE-1 (induced by source paper "fundamental limits of covert packet insertion"):
  with members:
    - "covert communication over a k user multiple access channel"
    - "fundamental limits of invisible flow fingerprinting"
    - "fundamental limits of covert bit insertion in packets"
    - "privacy preserving mhealth data release with pattern consistency"
    - "covert capacity of non coherent rayleigh fading channels"
    - "towards provably invisible network flow fingerprints"
    - "covert wireless communication with artificial noise generation"
    - "covert communication over noisy channels a resolvability perspective"

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"
    - "capacity of steganographic channels"
    - "lack a voip steganographic method"

Connected through hyperedge HE-3 (induced by source paper "on importance of steganographic cost for network steganography"):
  with members:
    - "steganography of voip streams"

Connected through hyperedge HE-4 (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"
    - "what are suspicious voip delays"
    - "steganography of voip streams"
    - "lack a voip steganographic method"
    - "covert channels in sip for voip signalling"
    - "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:
    - "steganography of voip streams"
    - "lack a voip steganographic method"
    - "covert channels in sip for voip signalling"
    - "new security and control protocol for voip based on steganography and digital watermarking"

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)