If you truly want to be secure, you need an air gap between your machine and the network. Nothing else is 100% effective.
Hey, if someone happens to guess your 4096-bit keyword, your crypto is broken... it could happen! The chances are 1 in 24096, but it could happen - therefore, no crypto is 100% secure! Yet, in practice, we can use that crypto, because it's practically impossible to guess that keyword. It's theoretically not 100% effective/secure, but it doesn't have to be to be usable.
I guarantee you the NSA has a full handbook full of undisclosed flaws they've found in linux and OSS software that they can exploit against any target they want, just like they have 0 day exploits for windows and proprietary software.
The NSA is not some kind of X Files or Men in black, they don't have any alien technology. Linux is used in many security-conscious applications, and security professionals are constantly auditing the code. A properly hardened Linux-system will not be easily penetrated by NSA, if the user doesn't do anything stupid.
It's kind of amusing actually - what you are asking for is DRM, isn't it? Some way of preventing an outside source from copying your private video. lol
Example: PGP is a way of preventing an outside source from reading your communications/viewing your data, it's an encryption method. A software used for privacy. The users have control here, only the sender and intended recipient of the communication/data have access to it. The key here is user control.
DRM is fundamentally user-hostile: it's a way of wresting the control of the computer away from the user. It's a way to make software/data "tamper proof", in order to prevent copying/unauthorized use/etc.
There's a very clear difference: one is for the benefit for the user, and is entirely controlled by the user. The other is user-hostile, and can never be in the user's control, can never be open-source.