Rumors that Apple will incorporate a fingerprint scanner into the iPhone 5S are once again surfacing.

According to a research note from KGI Securities analyst Ming-Chi Kuo, who has a pretty good batting average when it comes to Apple rumors, the iPhone 5S will indeed have a fingerprint scanner built in to the home button. This additional technology will necessitate a change hardware feature , however, as to accommodate the extra technology it will need to change from concave, as it has been since 2007, to a convex version. Additionally Kuo says that the home button will now feature a sapphire coating that will assist in keeping it from being scratched.

Convex home button creates space for fingerprint sensor; yield to improve. We think that a fingerprint sensor will be placed under the home button of iPhone 5S. However, assembling it could be difficult as the space under home button is limited as it already has to accommodate the Lightning connector, speaker and microphone. Thus, we think the shape of the home button could be changed from concave to convex to create more space for a fingerprint sensor.

Sapphire prevents home button from being scratched. A convex home button could be more easily scratched, so a harder material is required. We believe Apple will switch from plastic to sapphire, whose hardness is second only to diamond. Sapphire would protect the home button from being scratched and the fingerprint sensor from being damaged.

The addition of a fingerprint sensor to this year’s iPhone has been one of the most popular rumors going for some time now. We first saw it reported back in March, but it really picked up steam in July when references to fingerprint scanning were found in iOS 7 beta software.

With rumors that the iPhone 5S will make its debut on Sept. 10, we don’t have too long to wait to discover which rumors are true.