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: "ritm revocation in the middle"
  Abstract: Although TLS is used on a daily basis by manycritical applications, the public-keyinfrastructure that it relies on still lacks anadequate revocation mechanism. An ideal revocationmechanism should be inexpensive, efficient, secure, and privacy-preserving. Moreover, risingtrends in pervasive encryption pose new scalability challenges that a modern revocationsystem should address. In this paper, weinvestigate how network nodes can delivercertificate-validity information to clients. Wepresent RITM, a framework in which middleboxes (as opposed to clients, servers, or certificationauthorities) store revocation-related data. RITMprovides a secure revocation-checking mechanismthat preserves user privacy. We also propose totake advantage of content-delivery networks (CDNs) and argue that they would constitute a fast and cost-effective way to disseminate revocations. Additionally, RITM keeps certification authoritiesaccountable for the revocations that they haveissued, and it minimizes overhead at clients and servers, as they have to neither store nor download any messages. We also describe feasibledeployment models and present an evaluation ofRITM to demonstrate its feasibility and benefitsin a real-world deployment.

Connected through hyperedge HE-1 (induced by source paper "proxy certificates the missing link in the web s chain of trust"):
  with members:
    - "the rise of certificate transparency and its implications on the internet ecosystem"
    - "tracking users across the web via tls session resumption"
    - "pki safety net pkisn addressing the too big to be revoked problem of the tls ecosystem"

Connected through hyperedge HE-2 (induced by source paper "blockpki an automated resilient and transparent public key infrastructure"):
  with members:
    - "securify practical security analysis of smart contracts"
    - "pki safety net pkisn addressing the too big to be revoked problem of the tls ecosystem"
    - "keeping authorities honest or bust with decentralized witness cosigning"
    - "efficient gossip protocols for verifying the consistency of certificate logs"

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)