题 目：基于离散傅里叶变换（DFT）的数字水印算法研究
专 业：安全防范工程
作 者：
指导教师：
摘 要
数字水印（Digital Watermark）技术，是一种基于内容的、非密码机制的计算机信息隐藏技术。数字水印技术是属于图像隐藏技术的一个分支，在维护数字信息版权方面有着广泛的应用，具有较好的抗干扰能力和保密特性。它是将一些标识信息（即数字水印）直接嵌入数字载体当中（包括多媒体、文档、软件等）或是间接表示（修改特定区域的结构），且不影响原载体的使用价值，也不容易被探知和再次修改，但可以被生产方识别和辨认。
本课题主要研究基于离散傅里叶变换（DFT）的数字水印算法，通过Matlab软件仿真实现数字图像水印的嵌入和提取,变换域数字水印方法是先将图像变换到频率域，改变图像的频率域系数，然后进行反变换得到加入水印的图像，具体为：通过软件MATLAB进行算法的实现和仿真测试，本算法结合了Arnold置乱方法、经典相关性检测方法和傅立叶域特性，并在嵌入时采用嵌入两个不相关伪随机序列的方法，有效的提高了水印的安全性和相关性检测的准确率，是对经典相关性检测方法的一种改进。
实验结果表明，算法具有良好的不可见性，并且对于一般的图像处理操作具有良好的鲁棒性，性能优于传统的傅里叶域数字水印算法。
关键词：离散傅里叶变换；信息隐藏；数字水印；DFT；MATLAB
Title：Digital watermarking algorithm based on discrete Fourier transform (DFT) is studied
Speciality： Safety Precaution Project
Applicant：
Supervisor：
ABSTRACT
Digital watermarking (Digital Watermark) technology is a content-based, non-coded mechanism of computer information hiding technology. Digital watermarking technology is a branch of image hiding technology, which is widely used in the maintenance of digital information copyright, and has good anti-interference ability and confidentiality characteristics. It is to embed some identification information (i.e. digital watermarking) directly into the digital carrier (including multimedia, document, software, etc.) or indirectly (modify the structure of a specific area), and does not affect the use value of the original carrier, nor is it easy to be detected and modified again, but can be recognized and recognized by the manufacturer.
This paper mainly studies the digital watermarking algorithm based on discrete Fourier transform (DFT), which is embedded and extracted by Matlab software simulation. The transform domain digital watermarking method is to transform the image into frequency domain, change the frequency domain coefficient of the image, and then reverse transform to obtain the image with watermark. The algorithm is implemented and simulated by software MATLAB. The algorithm combines the Arnold scrambling method, the classical correlation detection method and the Fourier domain characteristics, and embeds two uncorrelated pseudorrelated random sequences when embedding, It effectively improves the security of watermark and the accuracy of correlation detection, and is an improvement of classical correlation detection method.
The experimental results show that the algorithm has good invisibility and robustness to the general image processing operation, and its performance is better than that of the traditional Fourier domain digital watermarking algorithm.
Keywords: discrete Fourier transform; information hiding; digital watermarking; DFT;MATLAB
