High Capacity Reversible Data Hiding in Encrypted Image Based on Intra-Block Lossless Compression

The cover image is generally encrypted by a stream cipher in existing reversible data hiding in encrypted image (RDHEI) methods. As pixel correlation is seriously damaged, more than one pixel should be employed to carry one bit such that the quite limited capacity is achieved. To overcome this issue, a new RDHEI method with high capacity, that preserves pixel correlation and exploits it to vacate embedding room, is proposed in this paper. First, we propose a block-level encryption scheme which combines block-level stream cipher and block-level permutation, and all blocks are classified into usable blocks (UBs) and unusable blocks (NUBs) by preserving the correlation of pixels in blocks. Then, UB is reconstructed to vacate room for data embedding, because the pixels in blocks share the same most significant bits (MSBs). To ensure reversibility, the number of NUBs between current UB and the previous one is also embedded along with additional data, and the blocks are rearranged in a reversible way such that UBs are always in front of NUBs. Experimental results show that not only the embedding capacity is significantly improved but also the hidden data can be losslessly extracted, and the cover image can be perfectly recovered.

Automated summary

This paper proposes a new RDHEI method that preserves pixel correlation to provide embedding space and solve the issues of damaged pixel correlation and limited embedding capacity in existing methods. The method utilizes block-level encryption scheme and block-level rearrangement to achieve reversible data hiding, significantly improving embedding capacity and enabling lossless extraction of hidden data.