论文标题

局部衰减:非数字查询的差异隐私通过局部敏感性

Local Dampening: Differential Privacy for Non-numeric Queries via Local Sensitivity

论文作者

Farias, Victor A. E., Brito, Felipe T., Flynn, Cheryl, Machado, Javam C., Majumdar, Subhabrata, Srivastava, Divesh

论文摘要

差异隐私是根据强大隐私保证的数据发布的最新正式定义。文献中已经提出了多种机制来释放数字查询的输出(例如,拉普拉斯机制和光滑的灵敏度机制)。这些机制通过向真实查询的输出添加噪声来确保差异隐私。添加的噪声量通过全局灵敏度和查询的局部灵敏度进行校准,这些概念衡量了个人对查询输出的添加或去除的影响。使用局部灵敏度的机制增加了更少的噪声,因此具有更准确的答案。但是,尽管已经进行了一些通用机制,用于使用全局灵敏度(例如,指数机制)释放非数字查询的输出,但文献缺乏使用局部敏感性来释放非数字查询输出的通用机制来降低问题的输出中的噪声。在这项工作中,我们纠正了这种缺点并呈现局部衰减机制。我们适应了非数字环境的局部灵敏度的概念,并利用它来设计一种通用的非数字机制。我们提供了与指数机制的理论比较,并在哪些条件下表明局部抑制机制比指数机制更准确。我们通过将其应用于三种不同的问题来说明局部衰减机制的有效性:(i)百分位选择问题。我们报告数据库中的第p-the元素; (ii)有影响力的节点分析。鉴于有影响力的指标,我们释放了最具影响力的节点,同时保留网络中节点之间关系的隐私; (iii)决策树归纳。我们提供对ID3算法的私人改编,以从给定的表格数据集构建决策树。

Differential privacy is the state-of-the-art formal definition for data release under strong privacy guarantees. A variety of mechanisms have been proposed in the literature for releasing the output of numeric queries (e.g., the Laplace mechanism and smooth sensitivity mechanism). Those mechanisms guarantee differential privacy by adding noise to the true query's output. The amount of noise added is calibrated by the notions of global sensitivity and local sensitivity of the query that measure the impact of the addition or removal of an individual on the query's output. Mechanisms that use local sensitivity add less noise and, consequently, have a more accurate answer. However, although there has been some work on generic mechanisms for releasing the output of non-numeric queries using global sensitivity (e.g., the Exponential mechanism), the literature lacks generic mechanisms for releasing the output of non-numeric queries using local sensitivity to reduce the noise in the query's output. In this work, we remedy this shortcoming and present the local dampening mechanism. We adapt the notion of local sensitivity for the non-numeric setting and leverage it to design a generic non-numeric mechanism. We provide theoretical comparisons to the exponential mechanism and show under which conditions the local dampening mechanism is more accurate than the exponential mechanism. We illustrate the effectiveness of the local dampening mechanism by applying it to three diverse problems: (i) percentile selection problem. We report the p-th element in the database; (ii) Influential node analysis. Given an influence metric, we release the top-k most influential nodes while preserving the privacy of the relationship between nodes in the network; (iii) Decision tree induction. We provide a private adaptation to the ID3 algorithm to build decision trees from a given tabular dataset.

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