基于自适应哈夫曼编码的密文可逆信息隐藏算法

随着云存储和隐私保护的发展,密文域可逆信息隐藏作为一种可以在密文中嵌入秘密信息,保证嵌入后的信息可以无错误提取,并能无损恢复原始明文图像的技术,越来越受到人们的关注.本文提出了一种基于自适应哈夫曼编码的密文域可逆信息隐藏算法,对不同的图像采用不同的哈夫曼码字编码腾出空间来嵌入秘密信息.首先利用自然图像相邻像素间的相关性对原始明文图像进行像素值预测,从最高有效位到最低有效位,对原始像素值和预测像素值的相同比特位进行自适应的哈夫曼编码标记.然后,利用流密码对原始明文图像进行加密.最后在腾出的空间,通过位替换来自适应的嵌入秘密信息.由于哈夫曼编码和解码的可逆性,合法接收者可以对原始明文图像和秘密信息实现分离的无损恢复和提取.实验结果表明,与现有的几种方法相比,本文提出的方法具有更好的安全性和更高的嵌入率,在BOSSBase、BOWS-2和UCID三个数据集上的平均嵌入率比MPHC算法分别提高了0.09bpp、0.062 bpp和0.06bpp,在最佳情况下比MPHC算法能分别高出0.958 bpp、0.797 bpp和0.320 bpp,最差情况下的嵌入率比MPHC算法也分别高出了 0.01 bpp、0.039 bpp和0.061 bpp.     

Separable reversible data hiding in encrypted images based on scalable blocks

This paper proposes a new separable reversible data hiding method for encrypted images. Proposed scheme employs the pixel redundancy of natural images to construct embedding space. First, cover image is divided into multiple blocks with different scales. According to the pixel average value of each block, the lowest two bits of every pixel are vacated as reserved rooms. Subsequently, the whole image is encrypted by using stream cipher and the secret messages are finally embedded into the reserved rooms by the embedding key. Proposed scheme is separable in the sense that the recipient can achieve different function by the following ways: (a) If the recipient has only decryption key, an approximation plaintext image containing the embedded information can be obtained. (b) If the recipient has only embedded key, secret messages can be extracted correctly. (c) If the recipient has both decryption key and embedded key, he can not only extract the secret messages, but recover the original cover image perfectly. Extensive experiments are performed to show that our proposed schemes outperform existing reversible data hiding schemes in terms of visual quality, embedding capacity and security performance, even if a large-scale image database is used.

     

High-payload completely reversible data hiding in encrypted images by an interpolation technique

We present a new high-payload joint reversible data-hiding scheme for encrypted images. Instead of embedding data in the encrypted image directly, the content owner first uses an interpolation technique to estimate whether the location can be used for embedding and generates a location map before encryption. Next, the data hider embeds the additional data through flipping the most significant bits (MSBs) of the encrypted image according to the location map. At the receiver side, before extracting the additional data and reconstructing the image, the receiver decrypts the image first. Experimental results demonstrate that the proposed method can achieve real reversibility, which means data extraction and image recovery are free of error. Moreover, our scheme can embed more payloads than most existing reversible data hiding schemes in encrypted images.     

基于图像秘密共享的密文域可逆信息隐藏算法

针对当前密文域可逆信息隐藏算法嵌入秘密信息后的携密密文图像的容错性与抗灾性不强,一旦遭受攻击或损坏就无法重构原始图像与提取秘密信息的问题,提出了一种基于图像秘密共享的密文域可逆信息隐藏算法,并分析了该算法在云环境下的应用场景。首先,将加密图像分割成大小相同的n份不同携密密文图像。然后,在分割的过程中将拉格朗日插值多项式中的随机量作为冗余信息,并建立秘密信息与多项式各项系数间的映射关系。最后,通过修改加密过程的内置参数,实现秘密信息的可逆嵌入。当收集k份携密密文图像时,可无损地恢复原始图像与提取秘密信息。实验结果表明,所提算法具有计算复杂度低、嵌入容量大和完全可逆等特点。在（3,4）门限方案中,所提算法的最大嵌入率可达4 bpp;在（4,4）门限方案中,其最大嵌入率可达6 bpp。所提算法充分发挥了秘密共享方案的容灾特性,在不降低秘密共享安全性的基础上,增强了携密密文图像的容错性与抗灾性,提高了算法的嵌入容量与云环境应用场景下的容灾能力,保证了载体图像与秘密信息的安全。     

Double linear regression prediction based reversible data hiding in encrypted images

Existing prediction-based works on reversible data hiding in encrypted images usually embed the secret messages by referring to the difference between current pixel and its predicted value. An accurate prediction model may promote an improvement of embedding capacity. Existing schemes, however, may not work well due to involving a bad prediction model so that their embedding capacity cannot be improved further. To address the problem, this paper proposes a new reversible data hiding scheme in encrypted images by designing double linear regression prediction model. Proposed model can significantly improve the prediction accuracy of current pixel based on neighboring pixels, more auxiliary rooms are thus vacated to embed secret data. Furthermore, a prediction error map is constructed to mark the error positions caused by inaccurate prediction, which can be further compressed lossless to lower the capacity of auxiliary data. Reversible recovery for original image can be finally achieved successfully. Experimental results demonstrate that the proposed scheme significantly improves prediction accuracy and data embedding capacity by combining double linear regression prediction model and prediction error map, and then can achieve separable and lossless recovery for the original image. Compared with existing works, the proposed scheme can implement a higher visual quality of decrypted images, while maintaining a larger embedding capacity.

     

基于位平面压缩的密文医学图像可逆信息隐藏算法

针对目前医学图像可逆信息隐藏算法嵌入容量小、需要对图像进行感兴趣区域（ROI）划分、接收方操作不灵活等缺点,结合医学图像特点,提出了一种基于位平面压缩的可分离式密文域信息隐藏算法。首先,将256级灰度医学图像分解成8个位平面,压缩高4个位平面,用峰值点像素值填充压缩后的空间,重构图像;然后,对重构的图像头部、中部、尾部分别加密;最后,在尾部根据嵌入密钥选取位置,通过直方图平移算法嵌入信息,接收方可根据密钥持有情况实现信息提取与图像恢复的可分离操作。实验结果表明,通过压缩图像预留空间来存放信息避免了辅助信息的传输,能有效提高嵌入容量,同时具有较高的安全性。     

基于细粒度嵌入空间预留的密文域图像可逆信息隐藏方法

针对云数据管理中的用户隐私保护需求,密文域图像可逆信息隐藏受到了学术界的广泛关注.基于加密前预留空间的数据嵌入框架将载体图像分割成由图像块组成的两个独立区域,使用传统的可逆信息隐藏技术腾出数据嵌入空间,可以取得较好的性能.为了更好地利用图像的空间相关性,提出了一种细粒度的可伸缩嵌入空间预留策略.该策略将图像块重新排列,...     

基于Paillier的可分离密文域可逆信息隐藏

为了提高信息嵌入率和实现直接解密后无损恢复原始图像,提出了基于Paillier的可分离密文域可逆信息隐藏算法.首先图像拥有者利用Paillier算法对图像进行加密后上传云服务器;而后信息隐藏者在云服务器中生成三个零矩阵,通过构造尺寸大小为2×2的填充分块进行信息嵌入;接收方根据不同的密钥,实现信息提取与图像解密的可分离.实验结果表明,相比于传统的可逆嵌入算法,该算法直接解密后不会存在失真的现象,并且最大嵌入率可达到2 bpp.     

Reversible data hiding in compressed and encrypted images by using Kd-tree

In this paper, a joint scheme and a separable scheme for reversible data hiding (RDH) in compressed and encrypted images by reserving room through Kd-tree were proposed. Firstly, the plain cover image was losslessly compressed and encrypted with lifting based integer wavelet transform (IWT) and set partition in hierarchical tree (SPIHT) encoding. Then, several shift operations were performed on the generated SPIHT bit-stream. The shifted bit-stream was restructured into small chunks and packed in the form of a large square matrix. The binary square matrix was exposed to Kd-tree with random permutations and reserving uniform areas of ones and zeros for secret data hiding. After that, a joint or a separable RDH scheme can be performed in these reserved spaces. In the joint RDH scheme, the secret data were embedded in the reserved spaces before encrypting with multiple chaotic maps. Thus, secret data extraction and cover image recovery were achieved together. In the separable RDH scheme, the secret data were embedded in the reserved spaces after encrypting with multiple chaotic maps. Since message extraction and cover image recovery are performed separately, anyone who has the embedding key can extract the secret message from the marked encrypted copy, while cannot recover the cover image. A complete encoding and decoding procedure of RDH for compressed and encrypted images was elaborated. The imperceptibility analysis showed that the proposed methods bring no distortion to the cover image because there was no change to the original cover image. The experimental results showed that the proposed schemes can perform better for secret data extraction and can restore the original image with 100% reversibility with much more embedding capacity and security. The proposed schemes significantly outperform the state-of-the-art RDH methods in the literature on compressed and encrypted images.

     

自适应的密文彩色图像可逆数据隐藏算法

为了提高直方图平移算法嵌入率和图像感知质量,提出一种自适应的密文彩色图像可逆数据隐藏算法。利用Logistics混沌置乱加密算法对彩色图像进行加密;对加密后的图像块根据设定的波动阈值自适应地分成平滑块和陡峭块;对平滑块进行高平面位比特替换,对陡峭块进行直方图平移和多比特位嵌入来提升嵌入率和图像质量。实验结果表明,该算法具有较高嵌入容量且感知质量较好,当嵌入率为1.142bpp时,峰值信噪比可达35dB以上,并且抵抗噪声、剪切攻击时鲁棒性较好。     

Separable data hiding in encrypted image based on compressive sensing and discrete fourier transform

Reversible data hiding in encrypted images has become an effective and popular way to preserve the security and privacy of users’ personal images. Recently, Xiao et al. firstly presented reversible data hiding in encrypted images with use of the modern signal processing technique compressive sensing (CS). However, the quality of decrypted image is not great enough. In this paper, a new method of separable data hiding in encrypted images are proposed by using CS and discrete fourier transform, which takes full advantage of both real and imaginary coefficients for ensuring great recovery and providing flexible payload. Compared with the original work, the proposed method can obtain better image quality when concealing the same embedding capacity. Furthermore, image decryption and data extraction are separable in the proposed method, and the secret data can be extracted relatively accurately.     

Reversible data hiding with context modeling,generalized expansion and boundary map

This paper proposes a reversible data hiding scheme with high capacity-distortion efficiency, which embeds data by expanding prediction-errors. Instead of using the MED predictor as did in other schemes, a predictor with context modeling, which refines prediction-errors through an error feedback mechanism, is adopted to work out prediction-errors. The context modeling can significantly sharpen the distribution of prediction-errors, and benefit the embedding capacity and the image quality. To expand prediction-errors, the proposed scheme utilizes a generalized expansion, which enables it to provide capacities larger than 1 bpp (bits per pixel) without resorting to multiple embedding. Besides, a novel boundary map is proposed to record overflow-potential pixels. The boundary map is much shorter compared with either a location map or an overflow map even though it is not compressed. The combination of the context modeling, the generalized expansion and the boundary map makes the overall scheme efficient in pursuing large embedding capacity and high image quality. Experimental results demonstrate that the proposed scheme provides competitive capacity compared with other state-of-the-art schemes when the image quality is kept at the same level.     

基于位平面分割的密文域可逆信息隐藏算法

针对传统密文域可逆信息隐藏算法嵌入率低的问题,为提高嵌入容量,提出一种基于位平面分割的可逆信息隐藏算法。首先对高位平面进行定长游程编码压缩,压缩结果进行流加密并作为其头部信息,利用压缩冗余嵌入数据;然后对中位平面进行Logistic混沌加密;最后将低位平面进行位翻转,利用AGM（Adaptive Group Modification）方法嵌入数据。实验表明,该方法实现简单,嵌入率不超过0.5bpp时,解密后携秘图像的PSNR≈47.8dB,实现了解密与提取的可分离,提取后再解密图像可100%恢复。     

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。     

A reversible data hiding scheme using complementary embedding strategy

Obtaining good visual quality and high hiding capacity with reversible data hiding systems is a technically challenging problem. In this paper, we propose a simple reversible data hiding scheme that uses a complementary hiding strategy. The proposed method embeds one secret bit horizontally and vertically into one cover pixel of a grayscale cover image by decreasing odd-valued pixels and increasing even-valued pixels by one. Experimental results show that the hiding capacity measured by bit per pixel (bpp) of the proposed scheme is at least 1.21 bpp with a PSNR (peak signal-to-noise ratio) value greater than 52 dB for all standard test images. Especially in the case of four-layer embedding, the PSNR value of the proposed method is still greater than 51 dB at a hiding capacity of about 5 bpp for all standard test images. In addition, the proposed method is quite simple because it primarily uses additions and subtractions. These results indicate that the proposed scheme is superior to many existing reversible data hiding schemes introduced in the literature.     

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。     

密文域高嵌入率图像全位面可逆数据隐藏

目的 针对现有的加密域可逆信息隐藏算法未能充分利用图像的全部位平面的问题,提出了一种密文域高嵌入率图像全位面可逆数据隐藏。方法 对载体图像进行加密,然后将隐蔽信息嵌入到加密图像中,进行隐蔽传输,发送给接收者。本文将灰度图像的8个位平面都用来进行数据嵌入,并把每个位平面划分成不重叠的块,分为非连续块（块内像素值0,1都存在）和连续块（块内为全0或全1像素值）,按块进行重排列且将排列前的块标签嵌入到重排列图像中,使用流密码对图像进行加密。在数据嵌入阶段,提出了带修正信息的像素预测方法用于非连续块的嵌入。连续块中,保持块内右下角像素值不变,用于连续块的恢复,其他位置嵌入数据;非连续块中,对预测正确的像素嵌入数据,预测错误的像素保持不变。结果 实验过程实现了多种密文域可逆数据隐藏算法,本文进行大量对比实验,并在BOSSbase和BOWS-2数据集上进行验证,与其他方法比较,本文方法在BOSSbase和BOWS-2数据集上的嵌入率分别提升了42.1%和43.3%。结论 提出的加密图像可逆数据隐藏方案,通过对不同性质的块采用不同方法进行数据嵌入,利用图像全位面信息,使得方案能够获得更高的嵌入率,表明了本文方法的有效性。     

自适应编码的高容量密文可逆信息隐藏算法

随着数字信息技术的普及,密文可逆信息隐藏(reversible data hiding in encrypted images, RDHEI)逐渐成为云存储中隐私保护的研究热点.RDHEI作为一种能在密文中嵌入额外信息,并正确提取嵌入信息和无损恢复原始图像的技术,受到研究者的广泛关注.为了能在加密图像中嵌入充足的额外信息,提出了一种自适应编码的高容量RDHEI算法.首先,计算原始图像不同预测误差的出现概率并自适应的生成哈夫曼编码;然后,利用流密码加密原始图像,根据像素预测误差对应的哈夫曼码字对加密后像素进行标记;最后,以位替换方式将信息嵌入到已标记像素的预留空间中.经实验验证:该算法在正确提取嵌入信息的同时,无损地恢复了原始图像.与同类算法相比,该算法充分利用了图像本身的纹理特性,有效地提高了图像嵌入率.在UCID,BOSSBase和BOWS-2这3个图像集上,该算法的平均嵌入率达到3.162bpp,3.917bpp以及3.775bpp,与当前性能最佳算法相比,提升了0.263 bpp, 0.292 bpp以及0.280 bpp.     

Adjustable prediction-based reversible data hiding

Reversible data hiding has received considerable interest recently in the field of information hiding. However, most of difference expansion (DE-based) schemes suffer from the problem that image cannot be restored into its original one free from location map. Reversible data hiding scheme with location map cannot effectively raise hiding capacity; in addition, it also incurs the computational cost during embedding and extracting. This study presents a reversible data hiding scheme that is free of location map and thus the computational cost, associated with embedding and extracting, is lower than that of most DE-based schemes. Furthermore, our scheme solves the problem of the low embedding rate of Tseng and Hsieh?s scheme because our scheme takes advantage of the bulk of relatively high small prediction-errors to raise embedding capacity. Experimental results demonstrate that the proposed scheme achieves the larger payload and the better image quality than some existing schemes by an adjustable control factor. The performance of the proposed scheme is more stable for the different images.     

结合Kd-树和熵编码的密文图像可逆数据隐藏

目的 密文图像可逆数据隐藏技术既可以保证载体内容不被泄露,又可以传递秘密信息,在军事、医疗等方面发挥着重要的作用。然而,以往的大多数方法存在图像冗余未被充分利用、数据嵌入容量不足等问题。为解决这些问题,提出了一种结合Kd-树和熵编码的高容量密文图像可逆数据隐藏算法。方法 该方法在图像加密之前需要对图像应用中值边缘检测(median-edge detector,MED)算法计算预测误差,并把得到的预测误差绝对值图像划分为两个区域:S0区域和S1区域。根据Kd-树标签算法和熵编码生成辅助信息,在对图像使用加密密钥K_e加密之后嵌入辅助信息,生成加密图像;在秘密数据嵌入阶段,根据附加信息和数据隐藏密钥嵌入秘密数据,生成载密图像;在解密阶段可以根据附加信息、图像加密密钥和数据隐藏密钥提取秘密数据并无损恢复图像。结果 实验测试了BOWS-2(break our watermarking system 2nd)数据集,平均嵌入容量为3.910 bit/像素。与现有的几种方法进行比较,该算法可以获得更高的秘密数据嵌入容量。结论 该方法在图像加密前腾出空间,与相关算法相比,实现了更高的嵌入容量,并且可以实现原始图像的无损恢复。