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: "spaced repetition and mnemonics enable recall of multiple strong passwords"
  Abstract: Abstract—We report on a user study that provides evidencethat spaced repetition and a speciﬁc mnemonic technique enableusers to successfully recall multiple strong passwords over time.Remote research participants were asked to memorize 4 Person-Action-Object (PAO) stories where they chose a famous personfrom a drop-down list and were given machine-generated randomaction-object pairs. Users were also shown a photo of a scene andasked to imagine the PAO story taking place in the scene (e.g.,Bill Gates—swallowing—bike on a beach). Subsequently, theywere asked to recall the action-object pairs when prompted withthe associated scene-person pairs following a spaced repetitionschedule over a period of 127+ days. While we evaluated severalspaced repetition schedules, the best results were obtained whenusers initially returned after 12 hours and then in 1:5 increasingintervals: 77% of the participants successfully recalled all 4stories in 10 tests over a period of ˇ 158 days. Much of theforgetting happened in the ﬁrst test period (12 hours): 89%of participants who remembered their stories during the ﬁrsttest period successfully remembered them in every subsequentround. These ﬁndings, coupled with recent results on naturallyrehearsing password schemes, suggest that 4 PAO stories couldbe used to create usable and strong passwords for 14 sensitiveaccounts following this spaced repetition schedule, possibly witha few extra upfront rehearsals. In addition, we ﬁnd statisticallysigniﬁcant evidence that with 8 tests over 64 days users whowere asked to memorize 4 PAO stories outperform users whoare given 4 random action-object pairs, but with 9 tests over 128days the advantage is not signiﬁcant. Furthermore, there is aninterference effect across multiple PAO stories: the recall rate of100% (resp. 90%) for participants who were asked to memorize1 PAO story (resp. 2 PAO stories) is signiﬁcantly better than therate for participants who were asked to memorize 4 PAO stories.These ﬁndings yield concrete advice for improving constructionsof password management schemes and future user studies.

Connected through hyperedge HE-1 (induced by source paper "bicycle attacks considered harmful quantifying the damage of widespread password length leakage"):
  with members:
    - "cash a cost asymmetric secure hash algorithm for optimal password protection"
    - "can t you hear me knocking identification of user actions on android apps via traffic analysis"
    - "naturally rehearsing passwords"
    - "calibrating data to sensitivity in private data analysis"
    - "de anonymizing social networks"

Connected through hyperedge HE-2 (induced by source paper "update tolerant and revocable password backup extended version"):
  with members:
    - "ransomware a rising threat of new age digital extortion"
    - "password generators old ideas and new"
    - "when privacy meets security leveraging personal information for password cracking"

Connected through hyperedge HE-3 (induced by source paper "usability of humanly computable passwords"):
  with members:
    - "towards human computable passwords"
    - "naturally rehearsing passwords"

Connected through hyperedge HE-4 (induced by source paper "client cash protecting master passwords against offline attacks"):
  with members:
    - "cash a cost asymmetric secure hash algorithm for optimal password protection"
    - "naturally rehearsing passwords"
    - "optimizing password composition policies"
    - "calibrating data to sensitivity in private data analysis"

Connected through hyperedge HE-5 (induced by source paper "cash a cost asymmetric secure hash algorithm for optimal password protection"):
  with members:
    - "client cash protecting master passwords against offline attacks"
    - "naturally rehearsing passwords"
    - "gotcha password hackers"
    - "optimizing password composition policies"

Connected through hyperedge HE-6 (induced by source paper "towards human computable passwords"):
  with members:
    - "analysis of boolean functions"
    - "human computable passwords"
    - "naturally rehearsing passwords"
    - "gotcha password hackers"
    - "optimizing password composition policies"
    - "on the complexity of random satisfiability problems with planted solutions"

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)