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: "a robust and secure aggregation protocol for wireless sensor networks"
  Abstract: The purpose of a wireless sensor network (WSN) is to provide the users with access to the information of interest from data gathered by spatially distributed sensors. Generally the users require only certain aggregate functions of this distributed data. Computation of this aggregate data under the end-to-end information flow paradigm by communicating all the relevant data to a central collector node is a highly inefficient solution for this purpose. An alternative proposition is to perform in-network computation. This, however, raises questions such as: what is the optimal way to compute an aggregate function from a set of statistically correlated values stored in different nodes; what is the security of such aggregation as the results sent by a compromised or faulty node in the network can adversely affect the accuracy of the computed result. In this paper, we have presented an energy-efficient aggregation algorithm for WSNs that is secure and robust against malicious insider attack by any compromised or faulty node in the network. In contrast to the traditional snapshot aggregation approach in WSNs, a node in the proposed algorithm instead of unicasting its sensed information to its parent node, broadcasts its estimate to all its neighbors. This makes the system more fault-tolerant and increase the information availability in the network. The simulations conducted on the proposed algorithm have produced results that demonstrate its effectiveness.

Connected through hyperedge HE-1 (induced by source paper "homomorphic encryption theory and application"):
  with members:
    - "security in wireless sensor networks"
    - "security and privacy issues in wireless mesh networks a survey"
    - "an attack on privacy preserving data aggregation protocol for wireless sensor networks"
    - "secure and privacy preserving data aggregation protocols for wireless sensor networks"
    - "secure and privacy preserving authentication protocols for wireless mesh networks"
    - "a novel mechanism for detection of distributed denial of service attacks"
    - "a mechanism for detection of gray hole attack in mobile ad hoc networks"
    - "reputation and trust based systems for wireless self organizing networks"

Connected through hyperedge HE-2 (induced by source paper "security in wireless sensor networks"):
  with members:
    - "a mechanism for detection of gray hole attack in mobile ad hoc networks"
    - "secure and privacy aware searching in peer to peer networks"
    - "an efficient and user privacy preserving routing protocol for wireless mesh networks"
    - "a distributed protocol for detection of packet dropping attack in mobile ad hoc networks"
    - "a distributed trust management framework for detecting malicious packet dropping nodes in a mobile ad hoc network"
    - "a distributed trust and reputation framework for mobile ad hoc networks"
    - "medians and beyond new aggregation techniques for sensor networks"

Connected through hyperedge HE-3 (induced by source paper "secure and privacy preserving data aggregation protocols for wireless sensor networks"):
  with members:
    - "an attack on privacy preserving data aggregation protocol for wireless sensor networks"
    - "reputation and trust based systems for wireless self organizing networks"
    - "internet of things applications and challenges in technology and standardization"
    - "a trust based detection algorithm of selfish packet dropping nodes in a peer to peer wireless mesh network"
    - "a survey on wireless sensor network security"
    - "a distributed trust and reputation framework for mobile ad hoc networks"
    - "medians and beyond new aggregation techniques for sensor networks"

Connected through hyperedge HE-4 (induced by source paper "secure and energy efficient data aggregation in wireless sensor networks"):
  with members:
    - "reputation and trust based systems for wireless self organizing networks"
    - "a distributed protocol for detection of packet dropping attack in mobile ad hoc networks"
    - "a trust based detection algorithm of selfish packet dropping nodes in a peer to peer wireless mesh network"
    - "a survey on wireless sensor network security"
    - "a distributed trust and reputation framework for mobile ad hoc networks"

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)