How to protect files in the application from theft?

Question

Mobile development

I want to show the user files in the application (of any format), but at the same time I want to be sure that the user will not be able to download the entire file on his own, but will be able to use it only within the application (there is always access to the Internet to download files). How can such interaction be organized?
Available:
- a permanent connection to the server
- a set of files for viewing
- a mobile or web application
Required:
- prohibit downloading or saving files
- prohibit the interception of traffic (for example, encrypt it as securely as possible, but in these matters my knowledge == 0)

Answer 1

videostream. Any other methods, when the final file somehow gets on the user's computer and is opened for viewing, are usually easier and cheaper to decrypt than to encrypt.

Answer 2

It won’t take off - these are the eternal questions of all law enforcement officers: how to let them listen to music so that they don’t download it, how to let them watch a movie so they don’t save it, how to show a photo ... and so on. We also need to come up with self-destructing content (along with the browser).
Everything that has been uploaded to the user can be saved, viewed, decrypted and distributed. Yes, you can even take a screenshot. Change your business model.
The more you try to protect the content, the more inconvenient it will be for the end user to work with it, as a result, the user will spit and go to others.
The guys from www.star-force.ru are doing this, go to them.