Information Hiding
and its Applications
Steganography and Watermarking
A detailed look at Steganography
   ◦ Text Steganography
   ◦ Hypertext Steganography
   ◦ Audio Steganography
   ◦ Image Steganography
   ◦ Steganography in Open System
Image Steganography Techniques
   ◦ Spatial Domain LSB Insertion
   ◦ Masking and Filtering
   ◦ DCT-based Steganography
   ◦ Wavelet-based Steganography
How to Detect Steganography
   ◦ Blind Detection
   ◦ Analytical Detection

Applications of Information Hiding

Several interesting applications may be achieved by using the techniques of information hiding. We briefly mention some of these applications:

1. Copyright Protection:

The pressing need of protecting intellectual property rights is the main driving force of the research in information hiding. A digital watermark representing the copyright information can be embedded into the media data so that the owners can claim their ownership of the data in court by extracting the watermark unambiguously if someone infringes on their copyright.

2. Fingerprinting:

The application of fingerprinting works in a slightly different way to protect the media content. To avoid unauthorized duplication and distribution of the multimedia content, an author can embed a distinct label as fingerprint into each copy of the data. If an unauthorized copy is found later, the origin of the copy can be traced by retrieving the fingerprint. Besides, if the fingerprint represents certain customers' personal information such as the credit card number, the original buyers will think twice before they distribute the received data to others because they will run the risk of spreading their own personal information around.

3. Authentication:

Multimedia data in digital format facilitate modifying and editing but problems arise when the possibly tampered data are to be used for legal purposes or the authenticity of the data is important to the users. In such situations, the data must be credible, the information content in the signal is not modified in transit to its destination. Information hiding provides a tamper-proofing tool for digital content. Once the content is manipulated, the embedded signal or watermark will be affected or even destroyed so that its status or existence can be used to verify the integrity of the content. Although authentication of media content can be achieved through conventional cryptographic techniques, the advantage of using information hiding is that the authenticator is inseparably bound to the content, which simplifies data handling.

4. Usage Control:

In some applications in which the multimedia content needs special hardware for copying or viewing, a digital watermark can be used to control the usage, such as the permission of viewing, listening or recording, etc. If the media player or recorder detects illegal copies based on an unmatched watermark, it will refuse to play or record the digital data.

5. Convert communication:

The nature of media data, such as images, audio and video, provides a good host for hiding the high-volume information in steganographic applications. By using the innocuous host media data as a cover, we may fool possible eavesdroppers to communicate with the trusted party secretly. From a communication viewpoint, the host media can be seen as a secret channel. Obviously, covert communication may be of military usage. Besides, some governments limit the usage of encryption services and information hiding may be a way to bypass the restriction.

6. Broadcast monitoring:

Broadcast monitoring is one of the potential applications that can be achieved by information hiding techniques. Advertisers, who pay the television or radio stations for commercial advertisements, would like to ensure those advertisements be broadcast as promised. The insertion and detection of the hidden signal may help them to verify this without involving much human effort for monitoring. Broadcast monitoring via information hiding can be achieved by either watermarking or steganography. We may embed the signal in some particular segments of the broadcast channels, which are available but not used for content transmission. The drawback is that special equipment may be required for handling the additional signal. Embedding a digital watermark in the media content as the controlled signal has the advantage of being fully compatible with the installed broadcast equipment. The primary disadvantage is its comparatively complicated embedding/detection process.

7. Annotation:

The bits embedded into the media data may comprise an annotation, giving further information about the media content. For example, a photographic image could be labeled to describe the time and place the photograph was taken, a procedure that could be done automatically by the processor in a camera. In multimedia databases, a digital watermark may represent a serial number or an index for efficient management. Besides, a digital watermark can be a flag to indicate types and properties of the content, which may possibly be used to track pornography on the network. In medical applications, embedding the date and patient's name in medical images could be a useful safety measure.

Reference:
Information Hiding in Digital Images: Watermarking and Steganography, by Po-Chyi Su, May 2003.