I installed SDK 15.3.0 build 59ac345 and started working though the DFU secure boot loader example. In the 15.3.0 documentation it says
You can find the source code and the project file of the example in the following folder: <InstallFolder>\examples\dfu\bootloader_secure_ble
But that boot loader_secure_ble directory isn't present. Did I miss a step here on installing the SDK?
RICHMAES-MBP:dfu richmaes$ pwd
RICHMAES-MBP:dfu richmaes$ ls -alrt
drwxr-xr-x 8 richmaes staff 256 Feb 14 13:06 open_bootloader
drwxr-xr-x 4 richmaes staff 128 Feb 14 13:15 secure_dfu_test_images
drwxr-xr-x 22 richmaes staff 704 Feb 14 13:19 secure_bootloader
drwxr-xr-x 18 richmaes staff 576 Mar 15 08:41 ..
drwxr-xr-x 6 richmaes staff 192 Mar 15 08:42 .
-rw-r--r-- 1 richmaes staff 631 Mar 15 08:42 dfu_public_key.c
You have probably done everything correctly. That folder location stated in the documentation is wrong. The correct folder location is "<project root>\examples\dfu\secure_bootloader", where you will find the folders for various development boards, then folders for the supported toolchains, then project files. This is also the case for SDK 15.2 (and possibly some earlier versions as well.)
Thank you for asking, this way we are aware of the issue and can correct it. We appreciate that!