Chi-Square Attack
Definition
A specific steganalysis test for LSB substitution in images. It tests whether pairs of pixel values that are related by flipping the LSB (called PoVs, pairs of values) appear with equal frequency, which they will when LSB substitution has been applied across the image.
- Target
- LSB substitution steganography in images
- Tests
- Frequency equality of pairs of values (PoVs)
- Basis
- LSB flipping pairs pixel values symmetrically
- Domain
- Steganalysis
Common questions
Why does LSB substitution create equal-frequency pairs of values?+
LSB embedding flips the least significant bit of a pixel toward a value that shares the same upper bits, so after embedding a message across many pixels, each pair of values that differ only in that bit tends toward equal occurrence, a statistical signature the chi-square test detects.
Does the chi-square attack detect all forms of steganography?+
It is specific to LSB replacement and similar bit-plane embedding, not to spread-spectrum, transform-domain, or matching-based methods that avoid the pair-of-values symmetry, so a negative chi-square result does not rule out other embedding techniques.
Related terms
- Adaptive Embedding
- A steganographic strategy that concentrates embedding changes in high-texture or high-noise image regions where they are perceptually and statistically harder to detect....
- Calibration
- A steganalysis technique that estimates the cover image statistics by cropping or decompressing and re-compressing the test image to produce a reference....
- Convolutional Steganalysis Network
- A deep neural network trained end-to-end to classify cover versus stego images. Architectures such as XuNet, SRNet, and Yedroudj-Net use learned high-pass...
- LSB Substitution
- Least-significant-bit substitution: the lowest-order bit of each sample value (pixel colour channel or audio sample) is overwritten with one bit of the...
- Rich Model (SRM)
- A high-dimensional feature set for steganalysis constructed from joint statistics of pixel prediction residuals computed with many different filter kernels and quantisation...