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: "security problems with improper implementations of improved fea m"
  Abstract: This paper reports security problems with improper implementations of an improved version of FEA-M (fast encryption algorithm for multimedia). It is found that an implementation-dependent differential chosen-plaintext attack or its chosen-ciphertext counterpart can reveal the secret key of the cryptosystem, if the involved (pseudo-)random process can be tampered (for example, through a public time service). The implementation-dependent differential attack is very efficient in complexity and needs only O(n^2) chosen plaintext or ciphertext bits. In addition, this paper also points out a minor security problem with the selection of the session key. In real implementations of the cryptosystem, these security problems should be carefully avoided, or the cryptosystem has to be further enhanced to work under such weak implementations.

Connected through hyperedge HE-1 (induced by source paper "cryptanalyzing an encryption scheme based on blind source separation"):
  with members:
    - "a general quantitative cryptanalysis of permutation only multimedia ciphers against plaintext attacks"
    - "on the design of perceptual mpeg video encryption algorithms"
    - "on the security of the yen guo s domino signal encryption algorithm dsea"

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)