While it is already possible to embed multiple watermarks within a single set of data, current watermark embedding techniques do not provide a sufficiently reliable method of determining the order in which the watermarks were embedded. An ability to preserve watermark order would have important uses in applications requiring knowledge of the sequence of access events, such as recording the last person to access a data record and for tracing the misuse of data.

Aston researchers have invented a reliable method of determining the order in which multiple watermarks are embedded in data. The technology uses blind source separation techniques, in which the departure from independence of a blind source decomposition is exploited, allowing the embedding and recovery of multiple watermarks in the order in which they were embedded. This is a rare property that has many potential uses and is a major advance over existing methods. The approach can be applied to single and multivariate time series, of still images, audio and video.

This technology is particularly useful for organizations that use confidential digital data, such as healthcare organizations deploying Picture Archiving and Communications Systems (PACS) systems, and military and intelligence-gathering organizations that need to protect sensitive data, such as satellite images or audio and video recordings of operations.