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: "steganography of voip streams"
  Abstract: The paper concerns available steganographic techniques that can be used for creating covert channels for VoIP (Voice over Internet Protocol) streams. Apart from characterizing existing steganographic methods we provide new insights by presenting two new techniques. The first one is network steganography solution which exploits free/unused protocols' fields and is known for IP, UDP or TCP protocols but has never been applied to RTP (Real-Time Transport Protocol) and RTCP (Real-Time Control Protocol) which are characteristic for VoIP. The second method, called LACK (Lost Audio Packets Steganography), provides hybrid storage-timing covert channel by utilizing delayed audio packets. The results of the experiment, that was performed to estimate a total amount of data that can be covertly transferred during typical VoIP conversation phase, regardless of steganalysis, are also included in this paper.

Connected through hyperedge HE-1 (induced by source paper "trends toward real time network data steganography"):
  with members:
    - "principles and overview of network steganography"

Connected through hyperedge HE-2 (induced by source paper "creativity in mind evaluating and maintaining advances in network steganographic research"):
  with members:
    - "security a perpetual war lessons from nature"
    - "principles and overview of network steganography"

Connected through hyperedge HE-3 (induced by source paper "synchronous relaying of sensor data"):
  with members:
    - "study of encryption and decryption of wave file in image formats"
    - "ant colony based routing for mobile ad hoc networks towards improved quality of services"
    - "sleep deprivation attack detection in wireless sensor network"
    - "grid security and integration with minimal performance degradation"
    - "data hiding techniques using prime and natural numbers"
    - "a semi distributed reputation based intrusion detection system for mobile adhoc networks"
    - "an lsb data hiding technique using natural number decomposition"

Connected through hyperedge HE-4 (induced by source paper "on importance of steganographic cost for network steganography"):
  with members:
    - "lost audio packets steganography the first practical evaluation"

Connected through hyperedge HE-5 (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"
    - "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-6 (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"
    - "lack a voip steganographic method"
    - "new security and control protocol for voip based on steganography and digital watermarking"

Connected through hyperedge HE-7 (induced by source paper "a survey on various data hiding techniques and their comparative analysis"):
  with members:
    - "steganography and steganalysis different approaches"
    - "an lsb data hiding technique using prime numbers"

Connected through hyperedge HE-8 (induced by source paper "towards steganography detection through network traffic visualisation"):
  with members:
    - "information hiding using improper frame padding"

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.MM(Multimedia)