Dropbox as fileserver?

I have been searching all over, but have not been able to find a clear answer for my problem.

I am working on an app, where some elements (images and audio) need to be stored online for retrieval when needed. At the same time, many of these files are protected by copyright and have kindly been lent to our client under the condition, that the files are only accessible through the app.

I don't have experience with setting up servers, but I thought dropbox might provide a simple solution, since the files only need to be on the server, and not be altered by the app. It's a one-way communication.

I have gotten it to work in a test with a public dropbox folder, however, it needs to be in a password protected folder, so people with the direct link still need to log on, just in case.

Hope someone can provide me with an answer as to how to do this, or at least point me in the right direction (or tell me, if the idea is bad ;) )