In this paper, we adapt the image lossless watermarking modulation proposed by De Vleeschouwer et al., based on the circular interpretation of bijective modulations, to the protection of medical relational databases. Our scheme modulates the numerical attributes of the database. It is suited for either copyright protection, integrity control or traitor tracing, being robust to most common database attacks, such as the addition and removal of tuples and the modification of attributes' values. Conducted experiments on a medical database of inpatient hospital stay records illustrate the overall performance of our method and its suitability to the requirements of the medical domain.

Databases represent today great economical and strategic concerns for both enterprises and public institutions. In that context, where data leaks, robbery as well as innocent or even hostile data degradation represent a real danger, and watermarking appears as an interesting tool. Watermarking is based on the imperceptible embedding of a message or watermark into a database in order, for instance, to determine its origin as well as to detect if it has been modified. A major advantage of watermarking in relation to other digital content protection mechanisms is that it leaves access to the data while keeping them protected by means of a watermark, independent of the data format storage. Nevertheless, it is necessary to ensure that the introduced distortion does not perturb the exploitation of the database. In this chapter, we give a general overview of the latest database watermarking methods, focusing on those dealing with distortion control. In particular, we present a recent technique based on an ontological modeling of the database semantics that represent the relationships in between attributes-relationships that should be preserved in order to avoid the appearance of incoherent and unlikely records.