Watermarking for Multilevel Access to Statistical Databases

Increased corporate, government and academic demand has prompted official statistics to release individual respondent data (microdata) in addition to the traditional tabular data. Microdata must be masked by a statistical disclosure control (SDC) method before being published, because otherwise the statistical confidentiality of respondents would be compromised. A novel application of watermarking is discussed in this paper which allows multilevel access to numerical microdata: depending on her clearance, the data user can remove more or less of the masking. Nonprivileged users just see the published data, but as the clearance of a user increases she can get a data set which is closer and closer to the original one.