Digital Watermarking Algorithm For Voyage Data Recorder Based On Wavelet Transformation

Voyage Data Recorder (VDR) can record ship navigation status and manipulation information, and take an important role on navigation safety on the sea and accident analysis. The massive sound and image data of VDR needs to be saved reliably, but they may be tampered deliberately or altered unconsciously. Therefore, it is an urgent problem to carry out effective security protection to the information collected and correctly analyze the causes of shipwreck. Digital watermarking is an important technique for protection of copyright of digital works. It embeds secret information into the digital works in order to prove its authenticity, but it can not reduce the value of works.In this paper, we research digital watermarking in discrete wavelet transform domain mainly. At first, this paper presents basic principle and typical algorithms of digital watermarking. And then, discuss four kinds of digital watermarking algorithms in DWT domain. (1) Bring forward a robust watermarking algorithm based on human visual system of radar images. Take radar image with DWT in YCbCr color space and analyse distributing feature of it. So use the method of redundant embedding. Combine of the characteristics of the human visual system to determine the minimum detectable difference of the image to achieve the maximum watermark embedding. Get good balance between the robustness and transparence of watermark. (2) Bring forward a multipurpose watermarking algorithm of radar images. Embed two kinds of watermark with different purpose in a radar image. For reducing the interference between the two watermarks, embed robust watermark in the middle-low frequence coefficients and fragile in the high frequence part of DWT in YCbCr color space which has a good effect. For increasing the security of watermark, use chaos system and public key arithmetic respectively to encrypt the robust and fragile watermarks before embedding. It makes the two kinds of watermark realize purpose and be difficult damaged. (3) Bring forward a watermarking algorithm based on human auditory system of driver's voice. It combine of characteristic of human auditory system to embed two-value image watermark in audio watermark. It use lift discrete wavelet transform to improve the operation speed of system and ensure the robustness and transparence of watermark. (4) Bring forward a dual watermarking algorithm which embeds two kinds of watermarking in different positions in DWT domain. For increasing the security of watermark, use chaos system and public key arithmetic respectively to encrypt the robust and fragile watermarks before embedding. And adjust the quantity step of watermark based on energy ratio. The experimental results show that the algorithms in the paper get to the expected effect.