human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "tandem securing keys by using a central server while preserving privacy"):
  Abstract: Users' devices, e.g., smartphones or laptops, are typically incapable of securely storing and processing cryptographic keys. We present Tandem, a novel set of protocols for securing cryptographic keys with support from a central server. Tandem uses one-time-use key-share tokens to, unlike traditional threshold-cryptographic solutions, preserve users' privacy with respect to a malicious central server. Additionally, Tandem enables users to block their keys if they lose their shares, and it enables the server to limit how often an adversary can use an unblocked key. We prove Tandem's security and privacy properties, and we empirically show that it causes little overhead using a proof of concept implementation. To illustrate Tandem's advantages we use it to secure attribute-based credentials keys using a central server without hurting the privacy properties provided by the credential system.

Includes members:
  Member "when a small leak sinks a great ship deanonymizing tor hidden service users through bitcoin transactions analysis":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "investigating mmm ponzi scheme on bitcoin")
  Member "when the cookie meets the blockchain privacy risks of web payments via cryptocurrencies":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "sok blockchain technology and its potential use cases")

Question: Please tell me which class the source paper 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)