目的 传统构造式图像信息隐藏算法通常直接将图像空域特征与秘密信息关联,对算法的安全性造成威胁。因此,本文将曲线绘制函数与信息隐藏相结合,提出一种以B样条控制点为特征,在图像空域间接隐藏信息的算法。方法 算法主要分为信息隐藏及信息提取两阶段。在信息隐藏阶段,发送方首先通过选取初始控制点、仿射变换及B样条曲线绘制生成多条参考曲线,然后利用曲线控制点的位置隐藏信息,最后为图像填充颜色,即完成含密纹理图像的构造。在信息提取阶段,提取方根据纹理曲线和图像颜色获得含密曲线及参考曲线,经对照计算即可提取出秘密信息。结果 本算法具有较高的隐藏容量、鲁棒性和安全性。实验结果表明,由本文算法生成的800×800像素图像,其最高隐藏容量可达2870bits,分别是另两种典型构造式信息隐藏算法的6.7和3.4倍,且在质量因子为10的JPEG（joint photographic experts group）压缩攻击下的提取误码率可低至0,优于鲁棒较强的选择式信息隐藏算法LDA-DCT（robust coverless image steganography based on DCT and LDA topic classification）以及与之类似的构造式信息隐藏算法。同时,抗隐写分析检测实验表明,在隐藏容量小于250bits时检测误差趋近于0.5。结论 本文以B样条曲线控制点为特征,在纹理图像的绘制过程中隐藏信息,有效提高了传统构造式图像信息隐藏算法的安全性、隐藏容量和鲁棒性。

Objective Information hiding techniques,including watermarking and steganography,have currently 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 through watermarking technology to protect the copyright of software or digital publications.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 easy detection.Therefore,some scholars have introduced coverless information hiding algorithms.Coverless information hiding does not mean secret communication without transmission media and does not modify the transmission media,realizingsecret information transmission by transmitting the original media without modification.The coverless information hiding algorithm can be divided into selective and constructed information hiding.Selective information hiding encodes or extracts features from the images in the image library and chooses the images corresponding to the secret information.By contrast,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 generally use visual signals such as pixels or patterns to hide the secret information directly in the image,resulting in a strong correlation between the image content and the secret information,which is easily identified by analyzing and detecting the image.Considering 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.The position of the control points is modified in accordance with the secret information.Therefore,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 and numbers and scrambles the subblocks for encryption.The midpoints of a group of subblocks are randomly selected to obtain a group of coordinate points as the initial control points of a B-spline curve.The control points of multiple groups of B-spline curves are then obtained by affine transformation of the initial control points.Consequently,the B-spline curves are drawn.The position of control points of each curve is changed in accordance with the secret information;that is,a texture image comprising stego curves is generated.Finally,the colors corresponding to the numbers of the selected subblocks are chosen 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 subblocks according to the colors of the stego image to calculate the initial control points.The edge detection of the stego texture image is conducted 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 variation 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 2 870 bits of secret information,which is 6.7 and 3.4 times of the hidden capacity of the two other texture constructive information hiding algorithms.The proposed algorithm has good robustness to common image attacks and has strong anti-JPEG compression capability.The SRNet algorithm is used for steganalysis,and the detection error is close to 0.5 when the hiding capacity is low,which indicates that detecting the proposed algorithm using traditional steganalysis algorithm is difficult.Conclusion In this paper,the control points of the 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,demonstrating its robustness to common image attacks and strong steganalysis resistance.