The single watermark algorithms always merely have a single function. In order to overcome this drawback

a multi-purpose dual watermark algorithm of color images based on the speeded up robust feature(SURF)is proposed in this paper. First

the original image was transformed from RGB to YUV space and the SURF points and vectors of original image are extracted. A 64-dimensional vector is constructed according to the main direction of the SURF point that meets the scale condition

then the vector is split into two 32-dimensional sub-vectors. The robust zero-watermarking sequence is produced by comparing the cosine angles between the sub-vectors and a secret reference vector. Then

the original image is divided into 2×2 sub-blocks and the fragile watermark is produced after XOR operations on the singular value norms of sub-blocks. Lastly

the fragile watermark is embedded into the least significant bit(LSB) in the space domain of the image original. copyright is identified by the bit correct rates(BCR)between the original robust zero-watermarking sequence and the watermark sequence extracted from the tested image. Content authentication is accomplished by judging whether the fragile watermark is consistent with the image least significant bit. The experimental results show that the algorithm not only has good invisibility and high computational efficiency

but also can achieve the dual function of copyright protection and content authentication.