Apple patents secure code

Apple, which is in the process of switching to computers based on the omnipresent Intel processor, has filed a patent application describing a method for securely running Mac OS X on specific hardware.

The Mac maker has applied for a patent to cover a "system and method for creating tamper-resistant code". Apple describes ways of ensuring that code can be limited to specific hardware, even in a world in which operating systems can be run simultaneously, in so-called virtual machines. The patent application was made in April of 2004, but only made public last Thursday.

In its application, Apple describes a means of securing code using either a specific hardware address or read-only memory (ROM) serial number. Apple also talks about securing the code while interchanging information among multiple operating systems. Mac OS X, Windows and Linux are called out specifically in the filing.

"This invention relates generally to the field of computer data processing and more particularly to techniques for creating tamper-resistant software," Apple says in its patent filing. Specifically, Apple refers to the technique of "code obfuscation", in which software makers employ techniques that make it harder for those using debuggers or emulators to figure out how a particular block of code is working.

Apple's patent application comes as the company prepares to offer its Mac OS X operating system for Intel-based chips, with the first machines scheduled to go on sale next year.

Historically, the company has had to worry less about the Mac running on non-Apple hardware because it has used different chips and other components from those that power Windows PCs. With its move to Intel chips, though, the innards of the Mac will become more similar to those of its Windows-based counterparts.

The company said it is not planning on supporting Windows or other operating systems on the Intel-based Macs it sells but has also said it doesn't plan on taking steps to prevent Mac owners from running other operating systems.

"We won't do anything to preclude that," Apple Senior Vice-president Phil Schiller told ZDNet UK's sister site, CNET News.com, in June.

However, Schiller also said Apple has no plans to allow its operating system to run on non-Apple hardware. "We will not allow running Mac OS X on anything other than an Apple Mac," he said. An Apple representative declined to comment on Wednesday on the patent filing. Clearly, though, Apple is gearing up the intellectual property push around the Intel move.

The company has reportedly been beefing up the technology that constrains the Intel versions of Mac OS X to run only on authorised machines, to this point a set of test Macs given to developers. The company has also applied for a trademark on Rosetta, its technology for running existing Mac programs on the Intel chips.