关键词: 奇异值分解（SVD）变换, 盲水印, 量化步长, 直流系数

Abstract: Combining SVD transform，this paper proposes a blind digital watermarking algorithm based on DC coefficients of DCT-domain.This algorithm executes DCT transform on each 8×8 block of the original image，and executes SVD transform on each 2×2 block of the collection of the DC coefficients.The quantization step Q is used to quantify the max singular value in order to embed the watermark in the result of the quantization.Because the DC coefficients are chosen for SVD transform，and the results of SVD represent the internal properties instead of the visual features，this algorithm gets a better robustness and transparency.The experiment results show that it can effectively resist the tampering attacks such as：median filtering，JPEG compression，noise and so on.The extraction process becomes very easy and convenient because it does not require the original image to involve in.

Key words: Singular Value Decomposition（SVD） transform, blind watermarking, quantization step, Direct Current（DC） coefficients