Speaking of the Department of Justice’s obsession with Apple, Jeremy Scahill and Josh Begley reported in an article last year for the Intercept on the CIA’s attempts to break their security measures:
By targeting essential security keys used to encrypt data stored on Apple’s devices, the researchers have sought to thwart the company’s attempts to provide mobile security to hundreds of millions of Apple customers across the globe. Studying both “physical” and “non-invasive” techniques, U.S. government-sponsored research has been aimed at discovering ways to decrypt and ultimately penetrate Apple’s encrypted firmware. This could enable spies to plant malicious code on Apple devices and seek out potential vulnerabilities in other parts of the iPhone and iPad currently masked by encryption. […]
The documents do not address how successful the targeting of Apple’s encryption mechanisms have been, nor do they provide any detail about the specific use of such exploits by U.S. intelligence. But they do shed light on an ongoing campaign aimed at defeating the tech giant’s efforts to secure its products, and in turn, its customers’ private data.
Apparently, iOS 9 — which was announced and released well after this article was published — made internal encryption far more difficult to break.