A Practical Privacy-Preserving Algorithm for Document Data

A huge number of documents such as news articles, public reports, and personal essays has been released on websites and social media. Once documents including privacy-sensitive information are published, the risk of privacy breaches increases; thus, documents should be carefully checked before publication. In many cases, human experts redact or sanitize documents before publishing; however, this approach is sometimes inefficient with regard to its cost and accuracy. Furthermore, critical privacy risks may remain in the documents. In this paper, we present a generalized adversary model and apply it to document data. This paper devises an attack algorithm for documents, which uses a web search engine, and proposes a privacy-preserving algorithm against the attacks. We evaluate the privacy risks for real accident reports from schools and court documents. As experiments using the real reports, we show that human-sanitized documents still include privacy risks, and our proposal would contribute to risk reduction.