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: "new security and control protocol for voip based on steganography and digital watermarking"
  Abstract: In this paper new security and control protocol for Voice over Internet Protocol (VoIP) service is presented. It is the alternative for the IETF's (Internet Engineering Task Force) RTCP (Real-Time Control Protocol) for real-time application's traffic. Additionally this solution offers authentication and integrity, it is capable of exchanging and verifying QoS and security parameters. It is based on digital watermarking and steganography that is why it does not consume additional bandwidth and the data transmitted is inseparably bound to the voice content.

Connected through hyperedge HE-1 (induced by source paper "micro protocol engineering for unstructured carriers on the embedding of steganographic control protocols into audio transmissions"):
  with members:
    - "on covert acoustical mesh networks in air"
    - "using transcoding for hidden communication in ip telephony"

Connected through hyperedge HE-2 (induced by source paper "an open source p2p encrypted voip application"):
  with members:
    - "proposed video encryption algorithm v s other existing algorithms a comparative study"
    - "comparative study of qos parameters of sip protocol in 802 11a and 802 11b network"
    - "an analysis of the skype peer to peer internet telephony protocol"

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"
    - "lack a voip steganographic method"
    - "covert channels in sip for voip signalling"

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"
    - "lack a voip steganographic method"

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"
    - "lack a voip steganographic method"
    - "covert channels in sip for voip signalling"

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"
    - "lack a voip steganographic method"
    - "covert channels in sip for voip signalling"

Connected through hyperedge HE-7 (induced by source paper "secmon end to end quality and security monitoring system"):
  with members:
    - "anap anonymous authentication protocol in mobile ad hoc networks"

Connected through hyperedge HE-8 (induced by source paper "steganography of voip streams"):
  with members:
    - "covert channels in sip for voip signalling"

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)