In image authentication research, a common approach is to divide a given image into a number of smaller blocks, and embed a fragile watermark into each and every block. The modifications can therefore be detected in the blocks that have been tampered with. The literature includes many authentication techniques for detecting modifications only. In this paper, we propose a method for recovering the damaged blocks using the magnitudes of DFT coefficients. If a given block is considered to be damaged, we divide it into 2x2 blocks, and replace the magnitude of the DFT coefficient F(0,0) with the corresponding magnitude of the original image. As the F(0,0) coefficients are always real, we quantized them and round them off. The file containing all of these coefficients are sent from the sender to the receiver using a public key scheme. As an image authentication system, we will use the scheme proposed by Wong and Memon. In their proposal, the image is partitioned into IxJ blocks, and a watermark is inserted into each block.