Another reason to own an Apple computer.

Internal document from the Drug Enforcement Administration complains that messages sent with Apple's encrypted chat service are "impossible to intercept," even with a warrant.

Apple has disclosed little about how iMessage works, but a partial analysis sheds some light on the protocol. Matthew Green, a cryptographer and research professor at Johns Hopkins University, wrote last summer that because iMessage has "lots of moving parts," there are plenty of places where things could go wrong. Green said that Apple "may be able to substantially undercut the security of the protocol" -- by, perhaps, taking advantage of its position during the creation of the secure channel to copy a duplicate set of messages for law enforcement.

Christopher Soghoian, a senior policy analyst at the American Civil Liberties Union, said yesterday that "Apple's service is not designed to be government-proof."

"It's much much more difficult to intercept than a telephone call or a text message" that federal agents are used to, Soghoian says. "The government would need to perform an active man-in-the-middle attack... The real issue is why the phone companies in 2013 are still delivering an unencrypted audio and text service to users. It's disgraceful."