Message digests for photographic images and video contents

New multimedia database search tools require rapidity, compression, image
quality and copyright control. The two latter are often covered by embedding a
hidden watermark signal in the multimedia content. More effective and
recognized multimedia search methods are using hash functions. Hash functions
compute very short signatures characteristically very different from one media
to another. Typical requirement of hash functions are: easily computable,
provide short output bit length, and collision resistant.
In this thesis, an image hashing method for multimedia contents is presented
as an innovative solution for content identification and indexing. This new
one-way function for images extract some image features by different
computations along radial projections. The magnitude of change is related to
the amount of the change of the media (image, video). In watermarking, hashing
enables the creation of payloads that depend on the media content, and which
are thus resistant to the "copy attack" and collusion.
This thesis is available in the SIMILAR collection under the label « Presses
universitaires de Louvain » (ISBN 2-930344-58-X) and may be purchased online
at www.i6doc.com.