pi@fwipt01 ~ $ sudo wpa_passphrase Test_SSID passphrase_for_testing | sudo tee -a /etc/wpa_supplicant/wpa_supplicant.conf
network={
	ssid="Test_SSID"
	#psk="passphrase_for_testing"
	psk=7b0f850b9e4294e6d72a7acbbb8201f3e55aa15db9e582157e7905319dddc542
}

pi@wifi-gw:~ $ sudo vi /etc/wpa_supplicant/wpa_supplicant.conf
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=DE

network={
   ssid="SSID"
   psk="PASSWORD"
}