Abstract: In order to increase the capacity and robustness of watermarking, this paper presents a digital watermarking algorithm based on image size invariant visual cryptography. Firstly, the watermark of binary image is scrambled in order to reduce the pixel correlation. Then the low bit of carrier image is altered by using basic matrix of（2, 2）visual cryptography scheme and watermark value. Experimental results show the algorithm has better robustness performance under image processing attack. The method is accomplished easily and the embedded data is larger. It is a simple and reliable watermarking algorithm.

Key words: image size invariant, visual cryptography, basic matrix, least significant bit