Secure JPEG steganography by LSB+ matching and multi-band embedding
A new steganographic algorithm is proposed for JPEG images by modifying the block DCT coefficients. Firstly, an embedding algorithm called LSB+ matching is generated to approximately preserve the marginal distribution of DCT coefficients. We further divide the DCT coefficients into four frequency bands, including the direct current (DC), low-frequency, middle-frequency, and high-frequency. Via matrix encoding, low data hiding rate and high embedding efficiency are achieved in high-frequency band, while the hiding rate is increased in the middle-frequency and DC bands, and highest in the low-frequency band. In addition, a coefficient selection strategy is employed to make the hidden message less detectable. The proposed algorithm is implemented on a set of 10000 images and tested with four steganalytic algorithms. The experimental results show that it outperforms the F5, nsF5 and LSB+ algorithms in terms of detection accuracy for the JPEG images at various levels of quality.