What is rdh?

RDH likely refers to Reversible Data Hiding. Here's some information about it:

Reversible Data Hiding (RDH) is a technique used in various applications such as medical imaging, military imaging, and forensics. The goal of RDH is to embed additional data into a carrier medium (e.g., an image, audio, or video) without causing significant perceptual distortion, and, more importantly, to be able to perfectly recover the original carrier medium after the embedded data is extracted.

Key aspects of RDH include:

• Embedding Capacity: The amount of data that can be embedded into the carrier medium. Higher capacity is generally desirable.
• Perceptual Quality: The level of distortion introduced to the carrier medium due to the embedding process. Techniques aim to minimize this distortion.
• Reversibility: The ability to perfectly restore the original carrier medium after the embedded data is extracted. This is the defining characteristic of RDH and separates it from general data hiding techniques.
• Security: Concerns whether the embedding process is secure and resistant to attacks that might try to detect the presence of hidden data or extract the data without authorization.

Common techniques used in RDH are:

• Difference Expansion: Exploits the differences between neighboring pixel values to create space for embedding data.
• Histogram Shifting: Modifies the histogram of the carrier medium to create space for embedding.
• Prediction Error Expansion: Predicts pixel values and uses the prediction error to embed data.
• Integer Transform: Uses integer-based transforms to create space for embedding.

Applications of RDH:

• Medical Imaging: Embedding patient information into medical images while ensuring the integrity of the images for diagnostic purposes.
• Military Imaging: Embedding authentication data into military images to verify their authenticity and prevent tampering.
• Forensics: Embedding watermarks into forensic images to track their provenance and ensure their integrity.
• Copyright Protection: Embedding copyright information into media files to protect against unauthorized distribution.

RDH offers a balance between data hiding and carrier medium preservation, making it a valuable technique in applications where the integrity of the carrier medium is critical.