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: "padsteg introducing inter protocol steganography"
  Abstract: Hiding information in network traffic may lead to leakage of confidential information. In this paper we introduce a new steganographic system: the PadSteg (Padding Steganography). To authors' best knowledge it is the first information hiding solution which represents inter-protocol steganography i.e. usage of relation between two or more protocols from the TCP/IP stack to enable secret communication. PadSteg utilizes ARP and TCP protocols together with an Etherleak vulnerability (improper Ethernet frame padding) to facilitate secret communication for hidden groups in LANs (Local Area Networks). Basing on real network traces we confirm that PadSteg is feasible in today's networks and we estimate what steganographic bandwidth is achievable while limiting the chance of disclosure. We also point at possible countermeasures against PadSteg.

Connected through hyperedge HE-1 (induced by source paper "stegblocks ensuring perfect undetectability of network steganography"):
  with members:
    - "on importance of steganographic cost for network steganography"

Connected through hyperedge HE-2 (induced by source paper "hidden and uncontrolled on the emergence of network steganographic threats"):
  with members:
    - "a pattern based survey and categorization of network covert channel techniques"
    - "steganography in modern smartphones and mitigation techniques"
    - "stegtorrent a steganographic method for the p2p file sharing service"
    - "voip steganography and its detection a survey"
    - "sending hidden data via google suggest"
    - "using transcoding for hidden communication in ip telephony"
    - "how hidden can be even more hidden"
    - "steganographic routing in multi agent system environment"

Connected through hyperedge HE-3 (induced by source paper "influence of speech codecs selection on transcoding steganography"):
  with members:
    - "speex a free codec for free speech"
    - "using transcoding for hidden communication in ip telephony"
    - "steganography of voip streams"
    - "lack a voip steganographic method"
    - "new security and control protocol for voip based on steganography and digital watermarking"

Connected through hyperedge HE-4 (induced by source paper "principles and overview of network steganography"):
  with members:
    - "stegtorrent a steganographic method for the p2p file sharing service"

Connected through hyperedge HE-5 (induced by source paper "how hidden can be even more hidden"):
  with members:
    - "stream control transmission protocol steganography"
    - "information hiding using improper frame padding"
    - "steganography of voip streams"

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)