Reversible data hiding in encrypted images (RDHEI) is a technology that embeds data directly in the encrypted images without decryption or knowledge of the content of the images. However, it is difficult to vacate room from the encrypted image. This problem limits the embedding capacity of the existing RDHEI methods. In this paper, we propose a new RDHEI method designed to supply large embedding capacity without pre-processing of the original images. Using a block-level encryption scheme, the proposed method partially retains the spatial correlation in the high bit-planes of the encrypted image, while the content of the image is held securely. The data hider can compress the high bit-planes of the encrypted image to vacate high-capacity room using Huffman compression coding. In addition, image recovery and data extraction are separable and error-free at the receiver side. The receiver can retrieve the lossless original image without the embedded data using only an encryption key or by extracting the secret data directly from the encrypted image without decryption using only the data-hiding key. The experimental results and comparison proved that the proposed method performs better than previous methods in terms of embedding capacity and visual quality.

加密图像中的可逆数据隐藏 (RDHEI) 是一种将数据直接嵌入到加密图像中的技术，无需解密或了解图像的内容。然而，很难从加密图像中腾出空间。这个问题限制了现有 RDHEI 方法的嵌入能力。在本文中，我们提出了一种新的 RDHEI 方法，旨在提供大嵌入容量而无需对原始图像进行预处理。使用块级加密方案，所提出的方法在加密图像的高位平面中部分保留了空间相关性，同时安全地保存了图像的内容。数据隐藏器可以使用霍夫曼压缩编码压缩加密图像的高位平面以腾出大容量空间。此外，图像恢复和数据提取在接收端是可分离且无差错的。接收者可以仅使用加密密钥或通过直接从加密图像中提取秘密数据而无需仅使用数据隐藏密钥解密来检索没有嵌入数据的无损原始图像。实验结果和比较证明，所提出的方法在嵌入容量和视觉质量方面都优于以前的方法。