Abstract: This thesis introduces the concept of digital watermark，and proposes one kind of DCT-based blind encryption watermark algorithm.Using International Data Encryption Algorithm（IDEA） encrypt the watermark image pixel or image file，according to human visual frequency response theory determine watermark embedded position to achieve the blind watermark，then using discrete cosine transform relize data embedded and extracted.The experimental results show this algorithm can realize the encryption data blind watermark and this algorithm can effectively protect data.

Key words: blind watermark, discrete cosine transform, International Data Encryption Algorithm, human visual frequency response

摘要： 介绍了数字水印的相关概念，提出了一种基于离散余弦变换的加密图像盲水印算法。利用国际数据加密算法（IDEA）对水印图像像素或图像文件进行加密，根据人眼视觉频率响应理论确定水印嵌入位置以实现盲水印，利用离散余弦变换（DCT）实现数据的嵌入和提取。实验表明：提出的算法能够实现加密数据盲水印，并对水印数据提供有效的保护。

关键词: 盲水印, 离散余弦变换, 国际数据加密算法, 人眼视觉频率响应