Abstract:

In order to improve the security of YASS algorithm, a modified high-randomness YASS algorithm namedVHD-YASS is proposed based on the virtual embedding blocks and the origin dithering of quantizers. In this algo-rithm, in order to improve the randomness of the embedding position, a virtual 8×8 H-block, which is used asa substitution of regular 8×8 H-block in the conventional YASS algorithm for message embedding, is created byrandomly selecting an irregular region in each B-block. Then, the shifts of origins of odd/ even QIM (Quantiza-tion Index Modulation) quantizers are controlled by a secrete key to avoid the DCT coefficient clusters due to themessage embedding under the condition of long QIM step. Finally, the proposed algorithm is compared with theconventional YASS algorithm and with two other improved YASS algorithms by experiments. The results show that,at the same embedding rate, the proposed algorithm attains a maximum detectability of 0.614, which is dramaticallyless than the conventional one of 0. 983, and that VHD-YASS is an effective steganography scheme because it is oflarge anti-steganalysis capability, excellent visibility and low complexity.

Key words: YASS algorithm, virtual embedding block, quantizer, origin dithering, observation domain, stegano-graphy analysis