基于CDMA技术的多水印算法

将码分多址（CDMA）思想引入水印系统以实现多水印方案。在水印嵌入过程中，每一用户以自己的密钥作为种子生成一个伪随机分布的地址码，并用该地址码将自己的欲嵌入信息调制为载波信号，然后以相加的方式把载波信号叠加入载体。在提取时，该用户使用相同的地址码，通过计算地址码和载体之间的相关系数，从载体中提取自己的嵌入信息。实验证明该算法可以实现多个用户独立嵌入和检测自己的水印信息，完全能满足多水印的要求。

Multiple watermarking algorithm based on CDMA technique

Code division multiple access(CDMA) technique was conceptually introduced to watermarking system to realize multiple watermark resolution.Before the watermark embedded,each user used his private key as a seed to generate an address code subjected to pseudorandom noise distribution.Each watermark was modulated into a carrier signal with its corresponding address code.And then these carrier signals were added to host media.During watermark detection,using the same address code,each user extracted his watermark from the detected media via calculating the correlation coefficient between address code and watermarked vector of the detected media.The experiment results show that this scheme can embed and extract watermarks independently for each user and is capable of multiple watermarking.