  Recent study has found out that after multiple times of recompression, the
DCT coefficients of JPEG image can form an embedding domain that is robust to
recompression, which is called transport channel matching (TCM) method. Because
the cost function of the adaptive steganography does not consider the impact of
modification on the robustness, the modified DCT coefficients of the stego
image after TCM will change after recompression. To reduce the number of
changed coefficients after recompression, this paper proposes a robust
steganography algorithm which dynamically updates the robustness cost of every
DCT coefficient. The robustness cost proposed is calculated by testing whether
the modified DCT coefficient can resist recompression in every step of STC
embedding process. By adding robustness cost to the distortion cost and using
the framework of STC embedding algorithm to embed the message, the stego images
have good performance both in robustness and security. The experimental results
show that the proposed algorithm can significantly enhance the robustness of
stego images, and the embedded messages could be extracted correctly at almost
all cases when recompressing with a lower quality factor and recompression
process is known to the user of proposed algorithm.
