Paper: Resampling and the Detection of LSB Matching in Colour Bitmaps

Andrew D. Ker
Oxford University Computing Laboratory, Parks Road, Oxford, England

Security, Steganography, and Watermarking of Multimedia Contents VII,
San Jose, CA, USA., 17-20 January 2005, pp. 1-15

(Original SPIE Digital Library Link)

Abstract

We consider the problem of detecting the presence of hidden data in colour bitmap images. Like straightforward LSB Replacement, LSB Matching (which randomly increments or decrements cover pixels to embed the hidden data in the least significant bits) is attractive because it is extremely simple to implement. It has proved much harder to detect than LSB Replacement because it does not introduce the same asymmetries into the stego image. We expand our recently-developed techniques for the detection of LSB Matching in grayscale images into the full-colour case. Not everything goes through smoothly but the end result is much improved detection, especially for cover images which have been stored as JPEG files, even if subsequently resampled. Evaluation of steganalysis statistics is performed using a distributed steganalysis project. Because evaluation of reliability of detectors for LSB Matching is limited, we begin with a review of the previously-known detectors.

1. INTRODUCTION: LSB STEGANOGRAPHY
1.1. LSB Replacement and LSB Matching
1.2. Detectors for LSB Matching
1.3. Evaluation Methodology

2. DETECTORS BASED ON CLOSE COLOUR PAIRS
2.1. Westfeld’s Detector
2.2. Performance Analysis

3. HISTOGRAM CHARACTERISTIC FUNCTION DETECTORS
3.1. Harmsen’s HCF COM Detectors
3.2. Performance Analysis

4. NOVEL DETECTORS
4.1. HCF COM Detectors Calibrated by Resampling
4.2. Alternative Methods of Calibration
4.3. Totalling Colour Components

5. CONCLUSIONS