Hackers port iPhone 4S' Siri to rival devices

Apple's personal assistant cracked open

Hackers say they've reverse engineered the Siri personal assistant that debuted in last month's release of the iPhone 4S, a feat that allows them to make it work from virtually any device.

To back up their claim, the hackers – from the mobile-application developer Applidium – released a collection of tools on Monday that they say can be used to build Siri-enabled applications on devices that were never authorized to offer the proprietary Apple feature. The tools, written in the Ruby, C, and Objective-C languages, are the result of painstaking sleuthing into the way Siri communicates with a remote server Apple dedicates to the service.

"Today, we managed to crack open Siri's protocol," the Applidium developers wrote in a blog post. "As a result, we are able to use Siri's recognition engine from any device. Yes, that means anyone could now write an Android app that uses the real Siri! Or use Siri on an iPad!"

The chances of someone using the findings to mass produce a Siri app for unauthorized devices is slim, since the hack requires a valid iPhone 4S unique identifier to be sent to the server. That means Apple could easily revoke identifiers that are used an abnormally high number of times, or from an abnormally high number of different locations.

But there doesn't appear to be anything stopping individual iPhone 4S owners from using the hack to expand the number of devices that work with Apple's proprietary natural-language app.

The Applidium developers reverse engineered Siri by setting up their own HTTPS servers with an SSL, or secure sockets layer, certificate they signed themselves. That allowed them to observe the commands Siri sent to Apple's server, which is located at guzzoni.apple.com. They eventually found that the body of such requests is little more than a binary plist whose contents can be deciphered using the Mac OS X plutil tool.

Interestingly, Siri sends a huge amount of data to the Apple server, and it uses the Speex audio codec to compress raw audio data before it is transmitted. When Siri operates in text-to-speech mode, Apple's server applies a confidence score and time stamp to each word.

iPhone fans who are excited by the possibility of this hack are advised to move quickly. Apple has long killed iOS bugs that make jailbreaks possible shortly after they're discovered, so it wouldn't be surprising to see the closing of this hole that allows Siri to be ported to rival devices. ®

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