Cycle Counting under Local Differential Privacy for Degeneracy-bounded Graphs
<|reference_start|>Cycle Counting under Local Differential Privacy for Degeneracy-bounded Graphs: We propose an algorithm for counting the number of cycles under local differential privacy for degeneracy-bounded input graphs. Numerous studies have focused on counting the number of triangles under the privacy notion, demonstrating that the expected $\ell_2$-error of these algorithms is $\Omega(n^{1.5})$, where $n$ is the number of nodes in the graph. When parameterized by the number of cycles of length four ($C_4$), the best existing triangle counting algorithm has an error of $O(n^{1.5} + \sqrt{C_4}) = O(n^2)$. In this paper, we introduce an algorithm with an expected $\ell_2$-error of $O(\delta^{1.5} n^{0.5} + \delta^{0.5} d_{\max}^{0.5} n^{0.5})$, where $\delta$ is the degeneracy and $d_{\max}$ is the maximum degree of the graph. For degeneracy-bounded graphs ($\delta \in \Theta(1)$) commonly found in practical social networks, our algorithm achieves an expected $\ell_2$-error of $O(d_{\max}^{0.5} n^{0.5}) = O(n)$. Our algorithm's core idea is a precise count of triangles following a preprocessing step that approximately sorts the degree of all nodes. This approach can be extended to approximate the number of cycles of length $k$, maintaining a similar $\ell_2$-error, namely $O(\delta^{(k-2)/2} d_{\max}^{0.5} n^{(k-2)/2} + \delta^{k/2} n^{(k-2)/2})$ or $O(d_{\max}^{0.5} n^{(k-2)/2}) = O(n^{(k-1)/2})$ for degeneracy-bounded graphs.<|reference_end|>
@article{hillebrand2024cycle,
    title={Cycle Counting under Local Differential Privacy for Degeneracy-bounded
  Graphs},
    author={Quentin Hillebrand, Vorapong Suppakitpaisarn, Tetsuo Shibuya},
    journal={arXiv preprint arXiv:2409.16688},
    year={2024},
    archivePrefix={arXiv},
    eprint={2409.16688},
    primaryClass={cs.CR cs.DS}
}