A widely used method of embedding hidden data inside images by manipulating…
2026
A widely used method of embedding hidden data inside images by manipulating the Least Significant Bits (LSB) of pixel values belongs to which category of steganography ?
- A.
Transform-domain steganography
- B.
Spread spectrum steganography
- C.
Substitution-based steganography
- D.
Distortion-based steganography
Show answer & explanation
Correct answer: C
Concept: Image-steganography techniques are classified by where and how the secret data is embedded relative to the cover image. The standard categories are: substitution-based (spatial-domain) methods, which directly overwrite redundant, low-order elements of the raw cover data; transform-domain methods, which first convert the cover into another mathematical domain (e.g. frequency/coefficient space) and embed there; spread-spectrum methods, which scatter the secret across a wide portion of the spectrum using a spreading code; and distortion-based methods, which encode data through a known sequence of deliberate modifications recovered by comparison with the original.
Category | Defining mechanism |
|---|---|
Substitution-based | Directly overwrites redundant bits of the raw cover data (e.g. pixel values) with secret-data bits |
Transform-domain | Transforms the cover (e.g. via DCT/DWT) and embeds by adjusting the resulting coefficients |
Spread-spectrum | Spreads the secret across a wide frequency band using a pseudo-random spreading code |
Distortion-based | Applies a known sequence of deliberate changes and recovers data by comparing the result with the original |
Application: The stem describes manipulating the Least Significant Bits (LSB) of pixel values — this is a direct, in-place overwrite of low-order bits of the raw pixel data. No domain transform is involved, and no frequency spreading or distortion-comparison step is used; the secret bits simply replace the LSBs.
Rule out transform-domain: LSB embedding never transforms the image into another domain (no DCT/DWT step) before writing the secret bits, so this category does not fit.
Rule out spread-spectrum: LSB embedding writes each secret bit into one specific pixel’s bit position; it does not spread the signal across a range of frequencies using a spreading code, so this category does not fit.
Rule out distortion-based: LSB embedding is recovered by reading the same bit positions back, not by comparing a distorted cover against the original to infer changes, so this category does not fit.
Confirm substitution-based: LSB embedding is the textbook spatial-domain substitution technique — it overwrites redundant low-order pixel bits directly with the secret data, matching this category exactly.
Result: The described LSB manipulation is Substitution-based steganography.