system drive encryption question

[FHDATA]

hello,

I am not currently using debian as linux OS but
considering it ...


If I clean install debian (latest of course) and during
the install process have  its / (system drive)
encrypted with pass-phrase ....

then later on, can I add a key, residing on
a usb flash drive,  to that encryption?

if yes, is there a step-by-step method one can follow  to do that?



thank you,
F-