Abstract
Nowadays, more and more researchers are interested in reversible data hiding in encrypted images (RDHEI), which can be applied in privacy protection and cloud storage. In this paper, a new RDHEI method on the basis of hierarchical quad-tree coding and multi-MSB (most significant bit) prediction is proposed. The content owner performs pixel prediction to obtain a prediction error image and explores the maximum embedding capacity of the prediction error image by hierarchical quad-tree coding before image encryption. According to the marked bits of vacated room capacity, the data hider can embed additional data into the room-vacated image without knowing the content of original image. Through the data hiding key and the encryption key, the legal receiver is able to conduct data extraction and image recovery separately. Experimental results show that the average embedding rates of the proposed method can separately reach 3.504 bpp (bits per pixel), 3.394 bpp, and 2.746 bpp on three well-known databases, BOSSBase, BOWS-2, and UCID, which are higher than some state-of-the-art methods.
Highlights
Reversible data hiding (RDH) has gained increasing attention [1,2]
The reversible data hiding (RDH) methods based on the above technologies cannot be directly applied to encrypted images
We present a new high-capacity reversible data hiding in encrypted images (RDHEI) method by applying hierarchical quad-tree coding and multi-MSB prediction
Summary
Reversible data hiding (RDH) has gained increasing attention [1,2]. By applying this technique, additional data can be embedded into a multimedia cover [3], while data extraction and original cover recovery can be both realized without loss. In [26], Chen et al designed a block-based rearrangement mechanism and extended the run-length code to compress the MSB planes of the original image, which made full use of the redundancy in plaintext domain and effectively freed up the embedding room for secret data. In [27], Yin et al performed pixel prediction and compressed the differences between the original values and the predicted ones by Huffman coding They used the stream cipher to execute image encryption, and embedded additional data into the room vacated by the Huffman coding through multiple MSB substitution. The contributions of this paper include: (1) A hierarchical quad-tree coding scheme with high compression ratio is proposed; (2) data extraction and image recovery can be completed separately; and (3) our method outperforms some of the state-of-the-art methods in embedding rate.
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