The digital signature and watermarking methods are used for image authentication. Digital signature encodes the signature in a file separate from the original image. Cryptographic algorithms have suggested several advantages over the traditional encryption algorithms such as high security, speed, reasonable computational overheads and computational power. A digital watermark and signature method for image authentication using cryptography analysis is proposed. The digital signature created for the original image and apply watermark. Images are resized before transmission in the network. After digital signature and water marking an image, apply the encryption and decryption process to an image for the authentication. The encryption is used to securely transmit data in open networks for the encryption of an image using public key and decrypt that image using private key.