Late yesterday Apple released a very minor update to it’s iPhone operating system, iOS 5. Shortly after the phone’s release a few months ago, Apple released a build of iOS 5.0.1. Yesterday’s update is, confusingly, also iOS 5.0.1, but it is a slightly newer build of the software. The change is decidedly odd, as Apple usually does not release new builds of the same versions of its software, except in beta testing. The update seems even stranger, however, when you consider that iOS 5.1 is likely to drop fairly soon.

Initial reports were that it was unclear what exactly Apple had changed with the new build. That changed after a fairly well-known figure in the iOS jailbreak community, MuscleNerd, reported that the change had left the iPhone’s file system unencrypted.

What that means is that the files responsible for Siri, the iPhone 4S’s vaunted voice assistant feature, are now unencrypted and accessible to programmers. With access to those files, jailbreakers could port Siri to older devices without breaking Apple’s encryption, and therefore without violating Apple’s copyright. Apple has claimed that Siri would not work properly on older phones because they lack the processing power of the iPhone 4S. The app on which Siri is built, Siri Assistant, which was acquired by Apple last year, ran on the iPhone 4, as well as the iPhone 3GS.

Why Apple would have decrypted the file system is anyone’s guess. The likeliest explanation is that it was a mistake, and that either the update got published accidentally, or it was a rush job. If so, then we can expect it to be re-encrypted with iOS 5.1, if not sooner. In the meantime, however, we can probably expect ports of Siri to start showing up in the jailbreak community fairly soon.

[Hat Tip: Cult of Mac]