Crucial software application keys for the Apple iPhone Software Developer Kit (SDK) have been leaked on to the web - potentially enabling anyone to develop their own iPhone applications.

The catch, of course, is that the SDK isn't actually available until the end of February and Apple is sure to have invalidated the key by then... unless someone's preparing to leak the SDK as well.

The SDK key, which comprises a string of 32 numbers and letters, has appeared on two different websites - Austin Heap and Zibri - but no other information has been given, says The Unofficial Apple Weblog (TUAW).

Apple has created the Software Development Kit to bring true third-party applications to the iPhone. Third-party apps had been limited to web applications that run in the iPhone's Safari web browser - a move that was heavily criticised by some in the Mac developer community.

Hacking the iPhone

The availability of an SDK - and the application key to go with it - will also be a boon to third-party iPhone hackers who want to and have been developing their own apps outside the legitimate channels provided by Apple. Apple CEO Steve Jobs compared the hacking efforts to a cat and mouse game - with Apple being the mouse.

Hacking the iPhone has undoubtedly bought considerable benefits to some users, enabling them to bypass Apple's single-partner phone contract deals with the likes of AT&T and O2. Buying hacked or 'unlocked' phones was also the only way to get an iPhone in the UK before its launch here in September last year.

However, hacking is not without its problems - a quick whizz round the web will reveal hundreds of squealing iPhone owners (iPhowners) who had their baubles 'bricked' by a software update from Apple.

Malware beware?

More serious is the threat of malware on the iPhone. After all, if you're prepared to go to a dodgy source to install a third-party app, SDK or SDK key, what's to stop some malicious prankster from wreaking havoc on your phone by offering an apparently legit app?

FUD or not, one of the reasons Apple has limited the ability to develop third-party apps on the iPhone is precisely because it doesn't want a repeat of the malware problems that other mobile phone platforms like Windows Mobile have experienced. As Apple CEO Steve Jobs says on Apple's Developer Connection website:

"It will take until February to release an SDK because we're trying to do two diametrically opposed things at once - provide an advanced and open platform to developers while at the same time protect iPhone users from viruses, malware, privacy attacks, etc. This is no easy task.

"Some claim that viruses and malware are not a problem on mobile phones — this is simply not true. There have been serious viruses on other mobile phones already, including some that silently spread from phone to phone over the cell network. As our phones become more powerful, these malicious programs will become more dangerous. And since the iPhone is the most advanced phone ever, it will be a highly visible target.

"Some companies are already taking action. Nokia, for example, is not allowing any applications to be loaded onto some of their newest phones unless they have a digital signature that can be traced back to a known developer.

"While this makes such a phone less than "totally open," we believe it is a step in the right direction. We are working on an advanced system which will offer developers broad access to natively program the iPhone's amazing software platform while at the same time protecting users from malicious programs."