In this paper we present a securing patient medical images and authentication system to increase the security, confidentiality and integrity of medical images transmitted through the Internet. A public key encryption technique was used to encrypt the patient capturing fingerprint and then embed it into the patient medical image. The fingerprint has been encrypted using the Rivest-Shamir-Adelman (RSA) public-key encryption algorithm. Then, by embedding the encrypted patient's fingerprint using a technique for digital watermarking in the Discrete Cosine Transform (DCT) domain makes the medical image be robust to several common attacks. The experimental results on different medical imaging modalities demonstrate the efficiency and transparency of the watermarking system.