Apple's iOS 7 beta 4 reignites rumours that iPhone 6 killer feature is fingerprint sensor

News that Apple has released iOS 7 beta 4, the latest test version of its forthcoming mobile OS, is still making the rounds, but already one programmer has made a startling discovery.

London-based developer Hamza Sood uncovered some intriguing code in beta 4's 'BioMetricKitUI' folder that potentially confirms rumours that Apple's next iPhone will deliver fingerprint scanning technology.

The strings of code in question explicitly refer to a, "Photo of a person holding an iPhone in their right hand while touching the Home Button," as well as noting, "A fingerprint that changes colour during the setup process."

It's thought that the references relate to illustrations that will help users set-up their next-gen iPhone, strongly suggesting that a biometric fingerprint sensor will be incorporated into a redesigned Home button on the device.

Potential uses for the sensor include unlocking the iPhone, but there's also obvious scope for deployment by third-party apps for security and identity verification purposes.

Provided the necessary API is made available by Apple, it could mean that banks and other financial institutions provisioning iOS apps for their user base will replace user IDs, passwords, and customer numbers with a simple swipe of the index finger.

Biometric technology would also likely play a central role in the next Passbook app.

Apple has been linked with fingerprint scanning for some time now, with rumours frequently swirling that the next iPhone will integrate biometric technology - speculation that got louder after Apple snapped up security company AuthenTec for $365 million last year.

The next-generation iPhone - likely to be dubbed the iPhone 5S or the iPhone 6 - is being tipped for a September launch.

It's also thought that Apple may be flirting with the release of a more affordable iPhone, potentially dubbed the iPhone 5C.

Such a device would likely swap the iPhone's traditional glass and aluminium construction for a plastic build and feature more modest specifications.