Hi I can provide you with a Touch ID authentication sample for your project. Here is an overview:
+ I will provide a sample project with instructions on how to add this code into your own project. The code sample will be written in Objective-C.
+ The code will first evaluative if the device is capable for Touch ID input, and will fall back to your current method of password input on older devices.
+ On devices that have Touch ID the code will handle all edge cases, such as fail, cancelled by user, cancelled by system -- and of course SUCCESS :)
+ In the case of success I will add an instruction so that you can see where the user is authenticated.
Is your current project written in Objective-C? I can have this ready for you today or any time during the weekend. My bid is to provide the code example with clear instructions on how to implement it easily into your code, however I don't offer any support for the actual payment gateway code your are using, just how to bypass the password login but will be happy to help you best I can.
Regards,
Elliott McAllister