Preserving Privacy in Sequential Data Release against Background Knowledge Attacks

TL;DR

This paper demonstrates how sequential background knowledge can be exploited to breach privacy in serial data releases and proposes a defense method using Jensen-Shannon divergence to mitigate this risk.

Contribution

It introduces a formal model for sequential background knowledge attacks and presents a novel defense algorithm, filling a gap in privacy protection for sequential data releases.

Findings

Sequential background knowledge can be effectively mined and used to identify sensitive information.

The proposed Jensen-Shannon divergence-based defense outperforms existing solutions.

Extensive experiments validate the effectiveness of the proposed privacy-preserving technique.

Abstract

A large amount of transaction data containing associations between individuals and sensitive information flows everyday into data stores. Examples include web queries, credit card transactions, medical exam records, transit database records. The serial release of these data to partner institutions or data analysis centers is a common situation. In this paper we show that, in most domains, correlations among sensitive values associated to the same individuals in different releases can be easily mined, and used to violate users' privacy by adversaries observing multiple data releases. We provide a formal model for privacy attacks based on this sequential background knowledge, as well as on background knowledge on the probability distribution of sensitive values over different individuals. We show how sequential background knowledge can be actually obtained by an adversary, and used to identify with high confidence the sensitive values associated with an individual. A defense algorithm based on Jensen-Shannon divergence is proposed, and extensive experiments show the superiority of the proposed technique with respect to other applicable solutions. To the best of our knowledge, this is the first work that systematically investigates the role of sequential background knowledge in serial release of transaction data.