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: "towards a design philosophy for interoperable blockchain systems"
  Abstract: In this paper we discuss a design philosophy for interoperable blockchain systems, using the design philosophy of the Internet architecture as the basis to identify key design principles. Several interoperability challenges are discussed in the context of cross-domain transactions. We illustrate how these principles are informing the interoperability architecture of the MIT Tradecoin system.

Connected through hyperedge HE-1 (induced by source paper "verifiable smart contract portability"):
  with members:
    - "blockchain based supply chain traceability token recipes model manufacturing processes"
    - "towards application portability on blockchains"
    - "applying software patterns to address interoperability in blockchain based healthcare apps"
    - "an empirical analysis of smart contracts platforms applications and design patterns"
    - "casper the friendly finality gadget"

Connected through hyperedge HE-2 (induced by source paper "decentralized trusted computing base for blockchain infrastructure security"):
  with members:
    - "hyperledger fabric a distributed operating system for permissioned blockchains"

Connected through hyperedge HE-3 (induced by source paper "implementation of smart contracts using hybrid architectures with on and off blockchain components"):
  with members:
    - "on and off blockchain enforcement of smart contracts"
    - "scilla a smart contract intermediate level language"
    - "designing secure ethereum smart contracts a finite state machine based approach"
    - "runtime verification for business processes utilizing the bitcoin blockchain"
    - "optimized execution of business processes on blockchain"
    - "enigma decentralized computation platform with guaranteed privacy"
    - "when money learns to fly towards sensing as a service applications using bitcoin"

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)