Kerberos gained pre-eminence because it is clever, and because its developers, computer scientists at the Massachusetts Institute of Technology, released the source code, which let security experts around the world debug and refine the program line by line.

ECONOMIST: Microsoft

And in the meantime he's been spending his days on a hobby that periodically stuns the computer security world: seeking out cracks in the source code of Apple's iPhone, a device with more software restrictions than practically any computer on the market, and utterly obliterating its defenses against hackers.

FORBES: Magazine Article

While some of the deployed protocols are in the public domain, the source code for particular applications have not been released yet making it difficult for security researchers to render an informed opinion on its implementation.

FORBES: Pressure Increases On Silent Circle To Release Application Source Code