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 "messageguard retrofitting the web with user to user encryption"):
  Abstract: Users today share a great deal of private information on the Web. While HTTPS protects this data during transmission, it does not protect data at rest, nor does it protect user data from the websites which store or transmit that data. These issues can be addressed with user-to-user encryption, an approach where data is encrypted and decrypted at the user's computer and is opaque to websites. In this paper we present MessageGuard, the first system that retrofits the Web with user-to-user encryption and is designed to work with all websites, in all browsers, on all platforms. We demonstrate that MessageGuard operates out-of-the-box on 47 of the Alexa top 50 sites, has minimal performance overhead, and is rated as highly usable by study participants.

Includes members:
  Member "tls in the wild an internet wide analysis of tls based protocols for electronic communication":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "privacyscore improving privacy and security via crowd sourced benchmarks of websites")
  Member "we re on the same page a usability study of secure email using pairs of novice users":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "private webmail 2 0 simple and easy to use secure email")
  Member "private webmail 2 0 simple and easy to use secure email":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "enhancing email functionality using late bound content")
  Member "why johnny still still can t encrypt evaluating the usability of a modern pgp client":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "private webmail 2 0 simple and easy to use secure email")
  Member "johnny and jane analyzing secure email using two novice users":
    also connected through other hyperedges:
      (none)

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)