Which technique hides information in significant parts of the cover image, such as cropping and compression?

Which technique hides information in significant parts of the cover image, such as cropping and compression?

• A. Distortion Techniques
• B. Substitution Techniques
• C. Transform Domain Techniques
• D. Spread Spectrum Techniques

Answer: (C)

Transform-domain techniques embed hidden data into the image’s frequency components rather than directly into pixel values. These coefficients reflect the image’s meaningful structure, with low-frequency parts carrying the major content. By hiding data in these components, the secret information becomes tied to how the image is built rather than to a single pixel, so common processing like compression—which quantizes and alters these coefficients—can still preserve the payload, and cropping tends to affect the image content in ways that transform-domain methods can accommodate more robustly than simple pixel manipulation. In contrast, methods that alter pixel values directly or spread data in less integrated ways are more vulnerable to being removed or corrupted by cropping and compression.

Transform-domain techniques embed hidden data into the image’s frequency components rather than directly into pixel values. These coefficients reflect the image’s meaningful structure, with low-frequency parts carrying the major content. By hiding data in these components, the secret information becomes tied to how the image is built rather than to a single pixel, so common processing like compression—which quantizes and alters these coefficients—can still preserve the payload, and cropping tends to affect the image content in ways that transform-domain methods can accommodate more robustly than simple pixel manipulation. In contrast, methods that alter pixel values directly or spread data in less integrated ways are more vulnerable to being removed or corrupted by cropping and compression.