迭代贝叶斯更新在度量隐私下比传统方法更准,且可证明收敛性。
On the Consistency and Performance of the Iterative Bayesian Update
- 用迭代贝叶斯更新估计隐私保护数据分布,优于矩阵求逆等方法。
- 在度量隐私机制下,该方法误差显著更低,且随着样本增多趋于真实分布。
- 首次证明其一致性,适用于无限数据类型场景,适合隐私建模研究者。
在用户数据隐私保护的场景中,估计用户敏感属性的分布至关重要。局部隐私模型通过本地扰动机制使用户发布带噪数据,再由收集方进行分布估计。本文实验表明,在度量隐私机制下,迭代贝叶斯更新(IBU)显著优于矩阵求逆(INV)和RAPPOR等方法;而数学分析揭示了INV在此类机制下表现不佳的原因。相反,在典型局部差分隐私机制(如k-RR、RAPPOR)下,IBU与INV性能相当。此外,文献中声称IBU具有一致性(即随样本增加估计收敛于真值),但缺乏证明。本文首次基于其为最大似然估计的性质,给出正式一致性证明。最后,针对敏感数据为无限字母表的情况,提出适配IBU的新方法,使其仍能有效运行。
原文摘要 · Abstract (English)
In many situations, estimating the distribution of users' data concerning certain attributes is important. To facilitate this estimation while safeguarding users' privacy, the local privacy model is commonly employed, in which each user applies a local protection mechanism to release a noisy version of their original data to the data collector. The original distribution is then estimated using methods such as Matrix Inversion (INV), RAPPOR's estimator, and iterative Bayesian update (IBU). In this article, we experimentally demonstrate that IBU significantly outperforms the other methods when user data is protected through metric privacy mechanisms. We also explain the mathematical reason for the suboptimal performance of INV under those metric privacy mechanisms. Conversely, IBU exhibits performance similar to INV under typical mechanisms of local differential privacy, specifically the k-RR and RAPPOR. In addition, we investigate IBU's consistency, which is a crucial property as it means that the estimate converges to the true distribution as the number of data points increases. In the literature, IBU is claimed to be consistent, but there is no proof for this claim. We provide a formal proof of consistency leveraging the fact that IBU is a maximum likelihood estimator. Finally, we examine scenarios involving an infinite alphabet for sensitive data and propose a method allowing IBU to operate effectively in these situations.
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