The paper describes a possible implementation of a web service that allows a restricted group of authorized users to securely share a collection of medical images which they provide remotely, to constitute incrementally a database stored at the server which maintains a PKI. Watermarking technology is used for the identification of the originator and the recipient as well for the authentication of the images and embedding patient information in the related image. We devised a well known method to serve image authentication and invisible embedding of patient information. A 128-bit message authentication code based on the image digest is created, then this MAC as well as the encrypted patient info is embedded, in a reversible way, at pixels LSBs locations, after compressing them. The original image can hence be formally authenticated, and the patient information confidentially stored. For many doctors of under-development countries who aren?t connected at an HIS (Hospital Information System), the Internet is often the only accessible communication channel, so, the web-based architecture guarantees a low cost and reliable support to enhance collaborative research without defeating the secrecy and confidentiality required in their specific area.