A high stego-image quality steganographic scheme with reversibility and high payload using multiple embedding strategy

Tian’s method is a breakthrough reversible data embedding scheme with high embedding capacity measured by bits per pixel (bpp) and good visual quality measured by peak signal-to-noise ratio (PSNR). However, the embedding capacity and visual quality of this method can be significantly improved. Thus, we propose a simple reversible steganographic scheme in spatial domain for digital images by using the multiple embedding strategy. The proposed method horizontally and vertically embeds one secret bit into one cover pixel pair. The experimental results show that the proposed reversible steganographic method achieves good visual quality and high embedding capacity. Specifically, with the one-layer embedding, the proposed method can obtain the embedding capacity of more than 0.5 bpp and the PSNR value greater than 54 dB for all test images. Especially, with the five-layer embedding, the proposed method has the embedding capacity of more than 2 bpp and the PSNR value higher than 52 dB for all test images. Therefore, the proposed method surpasses many existing reversible data embedding methods in terms of visual quality and embedding capacity.     

利用像素置换的自适应可逆信息隐藏

目的 像素置换作为一种可逆信息隐藏方式具有良好的抗灰度直方图隐写分析能力,但嵌入容量偏小一直是其缺陷。针对这一问题,提出了一种基于像素置换的自适应可逆信息隐藏算法。方法 首先,与传统2×2像素块结构相比构造了尺寸更小的像素对结构,使得载体图像可以被更稠密地分割,为嵌入容量的提升提供了基数条件。其次,提出适用于该新像素结构的可嵌像素对（EPP）筛选条件,避免嵌入过程引起图像质量大幅下降。之后,根据EPP的灰度趋势差异对其进行自适应预编码,提高Huffman编码压缩比,进一步提升算法嵌入容量。最终,通过像素置换嵌入信息。结果 与2×2像素块结构的非自适应图像隐写算法相比,在同样保证灰度直方图稳定性的情况下该算法的PSNR提高了32%左右,嵌入容量提高了95%以上。其中自适应性对嵌入容量提升的贡献极大。结论 本文算法同时具有抗灰度直方图隐写分析能力与高嵌入容量性的可逆信息隐藏。算法构造了更高效的可嵌单位,并且针对不同载体图像的特点对其可嵌区域进行差异化编码。实验结果表明,本文算法在具有更好的不可见性的同时,嵌入容量得到大幅提升。     

Adaptive reversible watermarking with improved embedding capacity

Embedding capacity is one of the most important issues of the reversible watermarking. However, the theoretical maximum embedding capacity of most reversible watermarking algorithms is only 1.0 bits per pixel (bpp). To achieve a higher capacity, we have to modify the least significant bit (LSB) multiple times which definitely lowers the quality of the embedded image. To this end, this paper proposes a novel reversible watermarking algorithm by employing histogram shifting and adaptive embedding. Specifically, the amount of the embedded watermark is adaptively determined in terms of the context of each pixel. For pixels with small prediction error, we modify the second, third and even the fourth LSBs as well to embed more than one watermark bit. Consequently, the proposed method achieves the embedding capacity larger than 1.0 bpp in single-pass embedding as well as bringing relatively low embedding distortion. The superiority of the proposed method is experimental verified by comparing with other existing schemes.     

基于中值预测的四轮嵌入可逆信息隐藏算法

传统基于预测误差直方图平移的可逆信息隐藏算法大多通过固定顺序来扫描原始图像,从而进行数据嵌入,这种方式没有考虑图像本身的纹理信息,导致无效移位像素点较多,伪装图像视觉质量较差。为解决该问题,提出一种基于中值预测的四轮嵌入可逆信息隐藏算法,以在提高嵌入容量的同时降低伪装图像的失真率。利用相邻像素之间具有较强相关性的特点,在较小的误差值处聚集大量像素点,以得到更陡峭的预测误差直方图并提高嵌入容量。对每个像素点定义复杂度,根据复杂度的高低对预测误差进行排序,优先在图像平滑区域嵌入数据,从而有效减少无效移位像素点个数,降低伪装图像的失真率。实验结果表明,该算法的最大嵌入率可以达到0.3 bpp,在0.1 bpp的嵌入率下峰值信噪比高达55.15 dB,与非对称直方图算法、误差直方图移位算法等相比,其具有较高的嵌入容量和较小的视觉失真率。     

图像分区选择的像素值排序可逆数据隐藏

目的 基于像素值排序（PVO）的数据隐藏算法因其高保真的优越性受到广泛重视,并不断得到改进。本文提出一种图像分区选择思想,以进一步充分利用图像的嵌入空间,改善PVO算法的嵌入性能,提高载秘图像的信噪比。方法 原始PVO算法通常采用预测差值“1”进行数据隐藏,对平滑像素组有较好的利用率和隐蔽性,而对毛躁像素组隐秘性能明显下降,算法性能与图像像素分布情况密切相关。本文在PVO算法基础上提出图像分区选择的思想,首先,将原始图像分为若干区域,然后按移位率从小到大的顺序依次选择图像区域;其次,在每个区域中选择合适的嵌入预测误差;最后,按顺序在被选区域利用该区域的最优嵌入差值完成信息嵌入。结果 假设将图像划分为8×8个区域,对本文算法与原始PVO算法进行比较,当嵌入量为1×10⁴ bit时,Elaine图像的移位率由81.59%降为74.40%,载秘图像的峰值信噪比（PSNR）值由55.388 2提高为56.996 9,提高了1.608 7,采用其他图像并就不同嵌入量进行实验,各图像PSNR值均表现出不同程度的提高。其次,将图像分别划分为2×2、4×4、8×8、16×16个分区,当嵌入量为1×10⁴ bit时,Lena图像PSNR由原始PVO的59.204 6逐渐增加至60.846 9,其他图像在不同嵌入量时PSNR均随着分区数的增加而有不同程度的提高。结论 本文提出的基于图像分区选择的改进PVO算法,可根据像素分布情况增加对嵌入空间的利用,在相同嵌入量情况下,改进后的算法能够获得更高的PSNR值;在一定分区数量条件范围内,分区数量与图像PSNR值表现出正相关性,随着分区数量的增加,图像PSNR值随之增加;本文方法在一定程度上改善了嵌入容量,弥补了因分区数量增加带来的辅助信息增加的问题。     

Hiding secret data in images via predictive coding

This paper presents a prediction-based image-hiding scheme that embeds secret data into compression codes during image compression. This scheme employs a two-stage structure: a prediction stage and an entropy coding stage. The secret data is embedded into the difference values of a given image after the prediction stage is performed.According to the experimental results, the image quality is better than Jpeg-Jsteg and its improved scheme (Inform. Sci. 141 (1-2) (2002) 123). The average image quality of the stego-images in the proposed scheme is greater than 50 dB when the hiding capacity is 1 bit per pixel, whereas those values in Jpeg-Jsteg and scheme in Chang et al. (Inform. Sci. 141 (1-2) (2002) 123) are 37.04 and 33.73 dB, respectively. The hiding capacity of the proposed scheme is 65,536 bits when the hiding capacity is 1 bit per pixel, whereas it is 53,248 bits in scheme (Inform. Sci. 141 (1-2) (2002) 123) and less than 3000 bits in Jpeg-Jsteg.     

结合层次结构和直方图平移的无损数据隐藏

针对现有基于差值直方图方法利用原始图像结构关系上的不足,提出了一种基于层次结构和差值直方图平移的无损数据隐藏方法RDH-HSDHS。RDH-HSDHS利用原始图像数据块中像素的差值形成直方图,充分利用图像中相邻像素间的相关性嵌入数据,为了进一步利用数据块中的参考像素进行数据嵌入,将参考像素组成新的图像进行下一层水印嵌入,直到当前层的嵌入容量小于解码所需的附加信息的长度或隐秘图像质量小于给定阈值。实验仿真结果表明,RDH-HSDHS能较好利用原始图像的全局和局部特性,在嵌入容量和隐秘图像质量之间达到较好的折中,在隐秘图像质量超过30 dB的同时,嵌入容量大于0.75 bit/pixel。另外,与相似方法的性能比较证明了提出方法的优势。该方法能有效应用于高质量需求的图像载体中进行信息隐藏。     

Improved Dual-image Quality with Reversible Data Hiding Using Translocation and Switching Strategy

Dual-image reversible data hiding (RDH) is a technique for hiding important messages. This technology can be used to safely deliver secret messages to the recipient through dual images in an open network without being easily noticed. The recipient of the image must receive the two stego-images before the secret message can be completely retrieved. Imperceptibility is one of the main advantages of data hiding technology; to increase the imperceptibility, the quality requirements of the stego-images are relatively important. A dual steganographic image RDH method, called a DS-CF scheme that can achieve a better steganographic image quality using the center folding (CF) strategy. In this paper, we developed a translocation and switching strategy (TaS) to shorten the distances between the stego-pixel coordinates and the cover pixel coordinates after information being hidden. Compared with the DS-CF scheme, our proposed DS-TaS scheme can effectively improve the quality of the steganographic images at the same level of embedding capability. The experimental results show that the PSNR of our DS-TaS scheme at = 1 was 55.66 dB, which is an increase of 1.5 dB, and is 51.43 dB for = 2, 46.66 dB for = 3, and 40.91 dB for = 4. In addition, the PSNR values of the stego images was increased by 1.5, 0.29, 0.29, and 0.19 dB, respectively. This shows that our proposed dual-image RDH method can optimize the visual quality of the stego-images and is better than many other dual-image RDH techniques.     

改进的双线性插值算法在信息隐藏中的应用*

针对传统信息隐藏算法隐藏容量小和对图像质量影响较大的缺点,提出了一种新的信息隐藏算法。利用灰度级插值的方法来修改秘密信息嵌入点的像素灰度值,为隐藏秘密信息创造出更大的冗余空间;同时采用新的相邻像素差值计算方法以实现秘密信息的嵌入,使得嵌入大量秘密信息后,载密图像的质量得到很好的保证。实验结果表明,当PSNR＞40 dB时,最低也可以隐藏145 800 bit。与传统的算法相比,隐藏容量有了更大提升的同时,PSNR值也保持在很高的水平。     

Embedding capacity raising in reversible data hiding based on prediction of difference expansion

Most of the proposed methods of reversible data hiding based on difference expansion require location maps to recover cover images. Although the location map can be compressed by a lossless compression algorithm, this lowers embedding capacity and increases computational cost during the procedures of embedding and extracting. The study presents an adaptive reversible data scheme based on the prediction of difference expansion. Since each cover pixel generally resembles its surrounding pixels, most of the difference values between the cover pixels and their corresponding predictive pixels are small; therefore, the proposed scheme gains from embedding capacity by taking full advantage of the large quantities of smaller difference values where secret data can be embedded. The proposed scheme offers several advantages, namely, (1) the location map is no more required, (2) the embedding capacity can be adjusted depending on the practical applications, and (3) the high embedding capacity with minimal visual distortion can be achieved. Moreover, the experimental results demonstrate that the proposed scheme yields high embedding capacity by comparing the related schemes that are proposed recently.     

Reversible data hiding for high quality images using modification of prediction errors

In this paper, a reversible data hiding scheme based on modification of prediction errors (MPE) is proposed. For the existing histogram-shifting based reversible data hiding techniques, though the distortion caused by embedding is low, the embedding capacity is limited by the frequency of the most frequent pixel. To remedy this problem, the proposed method modifies the histogram of prediction errors to prepare vacant positions for data embedding. The PSNR of the stego image produced by MPE is guaranteed to be above 48 dB, while the embedding capacity is, on average, almost five times higher than that of the well-known Ni et al. techniques with the same PSNR. Besides, MPE not only has the capability to control the capacity-PSNR, where fewer data bits need less error modification, but also can be applied to images with flat histogram. Experimental results indicate that MPE, which innovatively exploits the modification of prediction errors, outperforms the prior works not only in terms of larger payload, but also in terms of stego image quality.     

基于自适应MSB与差值预测的大容量密文域可逆信息隐藏算法

为提高密文域可逆信息隐藏（reversible data hiding in encrypted images,RDH-EI）的嵌入容量,提出了一种基于自适应MSB（most significant bit）与差值预测的RDH-EI方案。首先将图像进行分块,然后进行块级加密和置乱以抵抗对于加密图像的分析。在嵌入数据阶段,对于自适应MSB预测的方法进行改进,将没有嵌入数据的块,利用部分块内像素之间差值很小的特点采用自适应差值预测的方法嵌入数据,以块中左上角像素为目标像素,用于预测其他像素从而腾出更多的嵌入空间。实验结果表明,所提方法具有可逆性和可分离性,并且在自适应MSB预测方法的基础上进一步提高了嵌入容量,对于512×512大小的灰度图像,平均嵌入容量提高了大约7 445 bit。     

基于码分多址复用的双重加密可逆信息隐藏

针对多数密文域可逆信息隐藏算法嵌入容量小、加密算法单一的问题,提出一种双重加密的方法,并利用码分多址复用（CDMA）的思想嵌入秘密信息。加密时将图像分块,先对像素块进行多粒度置乱加密,再对块中每个像素的中间2位用流密码加密。信息嵌入采用码分多址的思想,选取k个长为4的相互正交的矩阵嵌入k层秘密信息,利用矩阵的正交性实现秘密信息多层嵌入,在提高嵌入容量的同时保证了对像素点的较小改变。对不满足嵌入条件的像素块嵌入伪比特,可避免使用位置图。拥有信息提取密钥的合法接收者可以提取秘密信息;拥有图像解密密钥可以近似恢复原始图像;拥有两种密钥既可提取秘密信息又可无损恢复原始图像。实验结果表明,512×512灰度图像Lena在峰值信噪比（PSNR）大于36 dB时最大嵌入容量133 313 bit。所提算法增强了加密图像安全性,在保证可逆性的同时大大提高密文域可逆信息隐藏嵌入容量。     

自适应高容量医学图像可逆数据隐藏算法

提出了一种新的医学图像无损数据隐藏算法,根据医学图像特点,将隐秘信息分别嵌入在感兴趣区域和非感兴趣区域中。在非感兴趣区域中,采用自适应整数变换方法增大嵌入容量并控制失真;在感兴趣区域,采用最低有效位替换方法控制水印图像质量。实验结果表明,算法的嵌入容量在1.2bpp到1.7bpp之间,而峰值信噪比保持在43dB左右。与现有相关算法相比,嵌入容量具有明显优势并保持较高的图像质量。另外,本方法计算复杂度低,能方便应用于实际的医学信息系统中。     

彩色图像信息密写新方法

为实现彩色图像中的安全隐写,首先通过混沌映射算法将图像去相关处理,再经过离散正弦变换, 提出以彩色图像为载体的安全隐写方法,应用二值图像信息嵌入技术,将隐蔽信息隐藏在颜色分量的较高层位面中,可实现优良的隐蔽性和较大的嵌入量。所使用的二值图像数据隐藏方案包括一组完备的规则,能够准确判断边缘像素是否可承载嵌入数据,保证嵌入数据的无差错盲提取,并可引入密钥以增强安全性。实验表明,在彩色图像中数据嵌入量达到每像素1.5 b时视觉不可察觉,峰值信噪比保持在40 dB以上,直方图无异常,并能抵御多种有效的隐写分析算法,兼顾了隐蔽信息容量和安全性。同时,解决了含密图像进行压缩或作任何有损的格式变换、数据嵌入、信息提取、抵御隐写分析算法难题。     

Development of a data hiding scheme based on combination theory for lowering the visual noise in binary images

In order to raise the embedding capacity and simultaneously reduce the artifact effect caused by embedding secret messages into binary images, a novel data hiding method based on the combination theory is proposed. In the proposed scheme, a secret position matrix is designed to improve the hiding capacity which is capable of preventing the least distortion based on the combination theory. Our new scheme enables users to conceal more than one bit of secret data by changing at most one pixel in one subimage. We have derived a formula for computing the payload and the possible modification pixels of a block. Compared with the existing schemes in terms of the hiding capacity and the visual artifacts, as our experimental results show, the proposed scheme is capable of providing a better image quality protector even with a more efficient secret data hider.     

Quadruple Difference Expansion-Based Reversible Data Hiding Method for Digital Images

ABSTRACT

Lossless data hiding is a special type of data hiding technique that guarantees not only the secret data but also the ability of cover media to be reconstructed without any distortion. A latest lossless data hiding technique is proposed by Hong Lin Jin's that is based on hiding only one data bit in the spatial domain in gray-level image. However, this method uses double difference expansion to embed bits which results in a small embedding capacity. For this purpose, we propose an improved algorithm with the potential of increasing the payload capacity and maintaining good image quality. The proposed improved algorithm is characterized by two aspects. First, the proposed improved reversible data hiding scheme is enhanced to exhibit data hiding in color palette images. Second, the embedding level is improved by using quadruple difference expansion to guarantee the embedding of 2-bit data into color images. Experiments of the proposed improved method have been conducted over several well-known test images. The results show that the proposed improved method significantly improves the embedding capacity over Hong Lin Jin's scheme by the range of 15–35% for grayscale images and 20–46% for color images while still maintaining the quality of the stego-images.     

基于块参照像素的无损信息隐藏算法

提出一种具有高嵌入容量的图像无损信息隐藏算法。首先将载体图像分成互不重叠的子块,然后在每块中选定一个参照像素,并计算参照像素与块内其它像素的差。在像素差直方图移位产生冗余空间之后,机密信息就可以无损地嵌入到这些冗余空间中。该方法在机密信息提取后可完全恢复载体图像,而且提取机密信息和恢复载体图像不需要除机密信息长度之外的任何信息。实验结果表明了该算法的有效性。     

Huffman-code strategies to improve MFCVQ-based reversible data hiding for VQ indexes

Data hiding, which embeds secret data into cover media, is one type of technology used to achieve the multimedia security. A reversible data hiding method has the characteristic that the cover media can be completely reconstructed after secret data are extracted. Recently, some reversible data hiding schemes have focused on the vector quantization (VQ)-compressed format. Using the modified fast correlation vector quantization (MFCVQ) concept, Lu et al. proposed a reversible data hiding scheme for VQ-index tables. In this paper, a new MFCVQ-based scheme is proposed. Specifically, our method will enlarge the embedding capacities by embedding multiple bits into a VQ index, thereby reducing the compressed bit rates by applying the Huffman-code concept and the 0-centered classification. Experimental results indicate that this method has greater pure embedding capacities and fewer compressed bit rates than that of previous MFCVQ-based methods.     

A lossless data hiding scheme based on three-pixel block differences

This paper proposes a data hiding scheme that losslessly embeds a message into a cover image using the two differences—between the first and the second pixel as well as between the second and the third pixel—in a three-pixel block. In the cover image, an absolute difference between a pair of pixels is selected to embed the message if the number of pixel pairs with the difference in the image is the largest. To embed a bit “1” or “0”, the selected difference is increased by 1 or left unchanged, respectively. In the best case, a three-pixel block can embed two bits “11” and only the central pixel needs to be increased or decreased by 1. The average payload capacity among the test images can be up to 2.08 bits per pixel (bpp).