US Patent 10083196 Creating secure virtual databases storing masked data

A database storage system creates secure snapshots or virtual databases based on a source database that stores sensitive information. The database storage system applies a masking function to the sensitive data and stores the masked data in the secure snapshot. The database storage system creates secure snapshots that share masked database blocks with other secure snapshots. The database storage system shares masked database blocks by storing information identifying a previously created masked database block for a new secure snapshot. If a masked database block for the new secure snapshot is different from the previously created masked database block, the database storage system stores metadata including the difference between the two masked database blocks. The database storage system allows sharing any transformed database blocks across snapshot, if the transformed database blocks are obtained by applying a transformation function to data of the source database.