It did not work for Skype[1]. This conversation has been about security through obscurity. You're describing their competitive advantage because competitors couldn't build external interfaces to the protocol; that's not security a security win, it's a business win, as you said.

[1] http://en.wikipedia.org/wiki/Skype_security#Flaws_and_potent...

Please point out security flaws in Skype's voice protocol. That list is a list of problems and flaws with Skype's software (which is, in general, shit). It doesn't seem to document any crypto failures. The largest security failing listed there is that it pulls ads over an unencrypted connection.

For all we know, the core Skype protocol may be perfectly implemented. The Wikipedia link states there's no peer-review.

So because we can't study it we assume it's perfect? That's the essence of the fallacy of security through obscurity.

As a corollary, just because you can't do a quick Google search for 0days in iOS or Windows doesn't mean they exist. In fact they do, and they're bought and sold on black markets or are kept secret by governments and the like.

You don't assume something is secure because you can't readily access documented flaws. You assume something is secure when it has undergone rigorous peer review, which, as you stated, does not exist.

Your argument seems to be that you can't simply find a laundry list of Skype flaws floating around. This is true. But it says positively nothing about the security or lack of security regarding Skype's protocol.

You said flat-out it did NOT work. I'm saying that it's not determinable, and so far, no published security holes in Skype exist. In fact, no real good details exist, despite plenty of people trying. Skype's probably the most popular IM/Voice/Video protocol in the world.

I agree that Skype's protocol may be terrible. But you cannot state that obscurity didn't help. "No one" is even able to connect to Skype, let alone break it, at this point.