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: "cryptanalysis of a noncommutative key exchange protocol"
  Abstract: In the papers by Alvarez et al. and Pathak and Sanghi a non-commutative based public key exchange is described.#R##N#A similiar version of it has also been patented (US7184551).#R##N#In this paper we present a polynomial time attack that breaks the variants of the protocol#R##N#presented in the two papers. Moreover we show that breaking the patented cryptosystem US7184551#R##N#can be easily reduced to factoring. We also give some examples to show how#R##N#efficiently the attack works.

Connected through hyperedge HE-1 (induced by source paper "on the algebraic structure of e_p m and applications to cryptography"):
  with members:
    - "group key management based on semigroup actions"
    - "public key cryptography based on semigroup actions"

Connected through hyperedge HE-2 (induced by source paper "group key management based on semigroup actions"):
  with members:
    - "an active attack on a multiparty key exchange protocol"
    - "public key cryptography based on semigroup actions"

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.IT(Information Theory)