My problem is just that the proposed mechanism relies on already having an even more perfect mechanism, and thus cannot be the "only one", but is in fact strictly weaker than this other mechanism. So we have a contradiction, and we can get rid of the notion that there exists such a thing as an "unbreakable" system (or, alternatively, that it is a useful concept)
This is pretty powerful. It means that organization which and periodically move physical assets securely can send information in a manner that is secure even if quantum computers reach their full potential.
Incidentally, the mechanism for sharing the pad doesn't have to be 100% secure, as long as you can reliably detect any compromises. If someone opens the briefcase while it's in transit, you just generate new pads and send another briefcase. To compromise the system, an adversary has to compromise the pad in transit without being detected.
It is the good standard for crypto systems. Yes it's unworkable in practice but that's exactly why nobody really uses it. It is useful for teaching and making comparisons.
Before you send your submarine to sea for example, you can provide them with many gigabytes of one time pad. They can then use this for their most secret communication.
Lots of SSL sessions are going on right now. It only takes a vulnerability like CVE-2014-0160 to change the score by 100 or so.
Briefcases: 1 in the last day
SSL sessions: 100 in the last day
Edit: if only CVE-2014-0160 had some evocative name.
I wouldn't trust some keys that had been lying around on an unencrypted hard drive for 1,2,10 years!
In real-world implementations I think the security is probably based around a large number of men with guns.
Nit: I would consider one time pad to be a method of encryption.
Now for 1,2,10 years depending on your rate of communication you can communicate using the one time pad.
>why not just send the actual message via that mechanism?
The point is you only have to exchange pads periodically, not every time you communicate.