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 fast image encryption scheme based on chaotic standard map"
  Abstract: In recent years, a variety of effective chaos-based image encryption schemes have been proposed. The typical structure of these schemes has the permutation and the diffusion stages performed alternatively. The confusion and diffusion effect is solely contributed by the permutation and the diffusion stage, respectively. As a result, more overall rounds than necessary are required to achieve a certain level of security. In this paper, we suggest to introduce certain diffusion effect in the confusion stage by simple sequential add-and-shift operations. The purpose is to reduce the workload of the time-consuming diffusion part so that fewer overall rounds and hence a shorter encryption time is needed. Simulation results show that at a similar performance level, the proposed cryptosystem needs less than one-third the encryption time of an existing cryptosystem. The effective acceleration of the encryption speed is thus achieved.

Connected through hyperedge HE-1 (induced by source paper "on the security of a class of diffusion mechanisms for image encryption"):
  with members:
    - "chosen plaintext attack of an image encryption scheme based on modified permutation diffusion structure"
    - "a chaotic image encryption scheme owning temp value feedback"
    - "local shannon entropy measure with statistical tests for image randomness"
    - "breaking a chaotic image encryption algorithm based on modulo addition and xor operation"
    - "a general quantitative cryptanalysis of permutation only multimedia ciphers against plaintext attacks"
    - "on the design of perceptual mpeg video encryption algorithms"

Connected through hyperedge HE-2 (induced by source paper "chosen plaintext attack of an image encryption scheme based on modified permutation diffusion structure"):
  with members:
    - "cryptanalyzing an image encryption algorithm based on scrambling and veginere cipher"
    - "a chaotic image encryption scheme owning temp value feedback"
    - "breaking a chaotic image encryption algorithm based on modulo addition and xor operation"
    - "breaking an image encryption algorithm based on chaos"

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)