In step A1. ( https://devzone.nordicsemi.com/b/blog/posts/getting-started-with-nordics-secure-dfu-bootloader )
nrfutil.exe keys generate private.key
I got
C:\Users\george>nrfutil keys generate private.key
Usage: nrfutil keys [OPTIONS] KEY_FILE
Error: Got unexpected extra argument (private.key)
What is the problem here ?