How to implement a secure video streaming website?
This is quite a complicated problem with a lot of possible approaches; a whole book could be written about it (your question is probably too broad).

That said, have you checked out Videola?  Videola is a Drupal-based distribution for creating subscription-based websites.  It's made by Lullabot, one of the leading Drupal companies, and they use it to power their learning network, Drupalize.me.