【作者】 叶新友；

【导师】 张基温； 钱雪忠；

【作者基本信息】 江南大学 ， 轻工信息技术与工程， 2009， 硕士

【摘要】 随着WWW网络的发展,任何一个网络用户都可以很轻易地复制、传递信息。这给数据的传送带来了极大的方便的同时,又带来了安全上的问题。随之产生的一个问题是如何在网络上保护不同多媒体作品(视频、音频等)的版权。相应的解决措施有密码系统和数字水印。密码具有完整而严密的理论证明,并且实现起来方便可靠。但同时密码系统的应用要求数据的发送和接收者必须有共享的密码,并且,加密后的数据一旦被解密就不再有什么安全性,加密通常也会改变多媒体数据的形式。而数字水印则不同,它可以将有关作者以及其它的有关版权的信息加入到视频和音频数据中,并且一旦加入,非法用户就不可能在多项式时间内去除它,合法用户可以获取此信息来证明版权的有效性。所以数字水印在保护多媒体数据方面具有密码系统无法比拟的优越性。论文首先介绍了图像信息压缩的基本知识,以及静止图像压缩的国际标准JPEG。接着介绍了数字水印的一般知识。在分析传统水印算法的基础上,本着算法必须在实现上是比较简单、在理论上不太复杂、并且具有较好的健壮性和安全性原则,论文对传统水印算法进行了改进。实验表明:改进后的算法能够经受攻击者常见的攻击。攻击者为给系统提取水印制造足够的麻烦,必须对图像在感官上造成显而易见的变换,这时,经受变化的图像在一定程度上已经没有应用价值。改进后的算法在稳定性和安全性上有较大提高。更多还原

【Abstract】 With the development of World Wide Web, any network user can copy and transfer information easily, which makes data transmission quite convenient. At the same time, security problems follow. How to protect copyrights of all kinds of multimedia productions, such as video, audio etc. becomes an serious problem.Cryptography and digital watermark are two effective measurements. Cryptography has already been demonstrated by integrated and rigorous theories, which can be implemented conveniently and unfailingly. But during the application of cryptography, the sender and receiver must share the cipher. Besides, once the encrypted data is cracked, security is nothing. The form of encrypted data has changed also. Opposite to cryptography, the technology of watermark is able to add some kinds of information, such as authors, copyrights etc. to video and audio data. Qualified user can validate the copyright by getting the information. But unqualified user can’t obtain the information in the multinomial time. Therefore, watermark has unexampled superiority over cryptography in the part of multimedia data protection.In this paper, image information compression and the quiescence image compression international standard JPEG are introduced firstly. The basic knowledge of watermark is followed. Based on the following principals simply implement, simple theory security, traditional watermark algorithm is improved through analyzing it . Experiment results indicate that the improved algorithm can undergo familiar attacks.更多还原