Steve Jobs said Apple has resisted allowing third party developers to create iPhone and iPod Touch applications because of security concerns.

Apple's CEO posted an open letter, confirming reports that the iPhone SDK will be released in February 2008.

"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," wrote Jobs.

Jobs implied that the first iPhone SDK will be a step beyond what Nokia is doing with its developers. Nokia has a huge developer community that creates applications for both Java and Symbian-based phones, and Jobs said those applications require a digital signature to verify they have passed certain tests.

This has helped reduce growing concerns about smartphone security.

The iPhone has already faced its first security challenges. Security gurus like HD Moore have been releasing "rock solid" exploits that have been used by hackers and security professionals alike to allow albeit temporarily iPhone and iPod Touch applications.

Even if the flaws are fixed, Moore claimed that criminals can still exploit older flaws by rolling back the firmware to a pre-patched version. A Trojan released in 2005 used a similar firmware rollback on the Sony PlayStation Portable.

Apple still faces the challenge of striking the right balance between openness and security, however, it has acknowledged there are more options for keeping the iPhone secure than just limiting developers to Web- based applications.

"While this makes such a phone less than 'totally open', we believe it is a step in the right direction," said Jobs.