## 3 Proposed Method  
In the proposed method, the image is considered as two parts: the center and probably more important part, and the image's exterior part, as seen in Figure 1. In photographs, the important thing, person or the main object is usually centered or around the center. The main idea in this study is to watermark the center of the image with a robust watermark to prove ownership, with a watermark strength that does not degrade the fidelity of the image to a marked extent. After that, the center part and outer part are divided into blocks and the center blocks are paired with the outer blocks of the image, watermarking the image digest of the inner block to the outer block for authentication purpose.  
The center part is watermarked with a robust watermark to prevent someone who knows the algorithm from cropping only the center part and using it without permission. The center part is watermarked in the DWT domain with the method proposed in [20]. The DWT of the center part and watermarking are shown in Equations (3) and (4). The watermark is embedded into the low frequencies, which are located in the LL1 band. This watermark does not degrade fidelity very much. The watermarked images after the center part watermarking have a PSNR value of 57, which is a very high fidelity value. In this study, the main concern is the authentication part. Because of this, no experimental results for the robust watermark are provided. For those interested in the method and success of robust ownership watermarking that is used for the inner parts, please see [20].  
\[[\mathrm{LL1},\mathrm{LH}\mathrm{LL1},\mathrm{HH1}\leftarrow\mathrm{DWT}( \mathrm{Center\;Image})] \tag{3}\]  
\[\mathrm{LL1}\leftarrow\mathrm{LL1}+\alpha*(\mathrm{Binary\;Image\;Watmark}) \tag{4}\]  
As a next step, the \(LL1\) bands of the inner blocks are represented in binary form by making the values 1 that are greater than the threshold value and assigning a value 0 in other cases. The threshold value is decided so as to make the number of ones and zeros almost equal to each other in the whole inner part. This is done to embed the watermark in a more balanced way to decrease the negative effect on fidelity.  
In Figure 1, the center part is contoured with thick black lines. The center part is divided into blocks that are of reduced area compared to the outer block sizes. The algorithm depends on a prime number \(K1\). The prime number \(K1\) will be given to the authenticator program that is used on the other side. After making pairs of blocks, one from the inner part and one from the outer part, a binary image is calculated from the inner block and that binary image block is embedded in the corresponding outer block. The outer blocks are greater in size compared to the inner blocks. This offers greater precision on the inner part to decide which block(s) are changed. This is reasonable because, in most of the images, the important person or thing is generally placed in the center part of the image. Moreover,  
Figure 1: Image consisting of inner part and outer part divided into blocks.  
the watermark storing capacity of the outer block increases as the block size increases. In Figure 2, the difference in block size is shown more clearly.