郦姝伊, 韩彦芳, 乐燕芬, 姚恒, 秦川(上海理工大学)
目的 构造式信息隐藏是一种以秘密信息为驱动，通过生成含密载体实现信息隐藏的技术。传统的构造式信息隐藏算法通常将秘密信息以像素位置或图案样式等空域信息直接表示在生成图像中，导致图像内容与秘密信息的关联性较强，易通过对空域进行特征检测发现秘密信息。因此，本文提出一种基于B样条生成纹理图像的构造式信息隐藏算法，以B样条控制点作为含密特征并生成图像，实现秘密信息于图像空域的间接隐藏，有效提高了算法的安全性。方法 在信息隐藏阶段，发送方将空白画布分块、编号、置乱，通过随机选取一组图像子块获得初始控制点，利用仿射变换生成多组控制点，根据秘密信息改变控制点位置并绘制B样条曲线，即可生成含密纹理图像。最后选取初始控制点对应颜色填充图像，即获得最终的彩色含密纹理图像。在信息提取阶段，提取方同样对图像分块、编号、置乱，并根据接收图像的颜色获得B样条曲线的初始控制点，并对接收图像进行边缘检测提取纹理曲线。最后结合初始控制点与纹理曲线求解含密控制点，进而提取秘密信息。结果 本文算法所生成纹理图像的隐藏容量可随纹理样式的改变而改变，在生成800?800像素的彩色图像时，平均可隐藏2870比特秘密信息，为另两种典型的构造式信息隐藏算法隐藏容量的6.7及3.4倍。本文算法对多种JPEG压缩等常见图像处理攻击具有较好的鲁棒性。本文利用TLBP算法对生成的512?512像素图像进行抗隐写分析能力检测，实验结果表明，当隐藏容量小于250比特时检测误差趋近于0.5，含密纹理图像无法通过隐写分析算法检测出来。结论 本文利用B样条曲线的控制点为特征实现图像空域的间接信息隐藏，解决了传统构造式信息隐藏算法图像内容与秘密信息关联较强的问题。且此纹理图像生成算法的隐藏容量可灵活调整，对常见的图像攻击具有较强的鲁棒性，同时具有较强的抗隐写分析能力。
Constructive Information Hiding with B-spline Driven Texture Generation
Li Shuyi, Han Yanfang, Le Yanfen, Yao Heng, Qin Chuan(University of Shanghai for Science and Technology)
Objective Nowadays, information hiding techniques, including watermarking and steganography, have become effective and important applications for secret communication. For a country or an organization, information hiding technology can be used to realize the communication of confidential information, using watermarking technology to protect the copyright of software or digital publications. The information hiding technologies always realize information hiding by modifying the transmission carrier. However, with the continuous development of steganalysis technology, information hiding algorithms suffer from the risk of being easy to be detected. Therefore, some scholars put forward coverless information hiding algorithms. Coverless information hiding does not mean secret communication without transmission media, but does not modify the transmission media and realizes the purpose of secret information transmission by transmitting the original media without modification. The coverless information hiding algorithm can be divided into selective information hiding and constructed information hiding. Selective information hiding encodes or extracts features from the images in the image library, and selects the images corresponding to the secret information. Constructive information hiding is a technology that uses secret information as the driver to generate secret communications media to realize information hiding. However, traditional constructive information hiding algorithms usually use visual signals such as pixels or patterns to directly hide the secret information in the image, resulting in a strong correlation between the image content and the secret information, which is easy to be found by analyzing and detecting the image. In view of the widespread use of B-spline curves in computer graphics, this paper proposes a constructive information hiding algorithm based on B-spline to generate texture images. According to the secret information, the position of the control points are changed, so that the secret information is indirectly hidden in the image special domain and has no direct relationship with the spatial characteristics. Method In the information hiding stage, the hider first divides the blank canvas into blocks, numbers and scrambles the sub-blocks for encryption. And midpoints of a group of sub-blocks were randomly selected to obtain a group of coordinate points as the initial control points of a B-spline curve. Then, the control points of multiple groups of B-spline curves are obtained by affine transformation of the initial control points, and the B-spline curves are drawn by them in turn. The position of control points of each curve is changed according to the secret information, that is, a texture image composed of stego curves is generated. Finally, the colors corresponding to the numbers of the selected sub-blocks are selected from the color library to fill the texture image, that is, the construction of the color stego texture image is completed. In the information extraction stage, the extractor first blocks, numbers and scrambles the image with the same key, and then extracts the indexes of sub-blocks according to the colors of the stego image, so as to calculate the initial control points. And the edge detection of the stego texture image is carried out to obtain stego curves. Finally, the control points of stego curves are obtained by combining the stego curves and the initial control points, and then the secret information is extracted. Result The hidden capacity of the texture image generated by the algorithm in this paper can change with the change of texture shape. In the comparison experiment of hidden capacity, for the color image with the same size of 800×800 pixels, the algorithm in this paper can hide 2870bits of secret information, which is 6.7 and 3.4 times of the hidden capacity of the two other texture constructive information hiding algorithms respectively. The proposed algorithm has good robustness to common image attacks, and has strong anti-JPEG compression ability. The TLBP algorithm is used for steganalysis, and the detection error is closer to 0.5 when the hiding capacity is lower, which indicates that the proposed algorithm is difficult to be detected by traditional steganalysis algorithm. Conclusion In this paper, the control points of B-spline curve are used as features to realize indirect information hiding in image spatial domain, which solves the problem of strong management of image content and secret information in traditional constructive information hiding algorithm. The hidden capacity of this texture image generation algorithm can be adjusted flexibly, and it has strong robustness to common image attacks and strong steganalysis resistance.