  Recently, a significant amount of interest has been developed in motivating
physicians to use e-health technology (especially Electronic Medical Records
(EMR) systems). An important utility of such EMR systems is: a next generation
of Clinical Decision Support Systems (CDSS) will extract knowledge from these
electronic medical records to enable physicians to do accurate and effective
diagnosis. It is anticipated that in future such medical records will be shared
through cloud among different physicians to improve the quality of health care.
Therefore, right protection of medical records is important to protect their
ownership once they are shared with third parties. Watermarking is a proven
well known technique to achieve this objective. The challenges associated with
watermarking of EMR systems are: (1) some fields in EMR are more relevant in
the diagnosis process; as a result, small variations in them could change the
diagnosis, and (2) a misdiagnosis might not only result in a life threatening
scenario but also might lead to significant costs of the treatment for the
patients. The major contribution of this paper is an information-preserving
watermarking scheme to address the above-mentioned challenges. We model the
watermarking process as a constrained optimization problem. We demonstrate,
through experiments, that our scheme not only preserves the diagnosis accuracy
but is also resilient to well known attacks for corrupting the watermark. Last
but not least, we also compare our scheme with a well known threshold-based
scheme to evaluate relative merits of a classifier. Our pilot studies reveal
that -- using proposed information-preserving scheme -- the overall
classification accuracy is never degraded by more than 1%. In comparison, the
diagnosis accuracy, using the threshold-based technique, is degraded by more
than 18% in a worst case scenario.
