C:Program Files (x86)Androidsdkplatform-tools>adb devices
List of devices attached
007667324ccb229b        unauthorized

cd ~/.android
adb push adbkey.pub /data/misc/adb/adb_keys

adb kill-server
adb start-server

delete the computers adb key: rm /data/misc/adb/adb_key on device

(I have no idea if in case of multiple authorized computers the additional keys are in a new line of the file or if they are in new files. I have only 1 computer.)

stop all adb processes "killall adb" in linuxoids and "taskkill /IM adb.exe" in windows or simply the taskmanager in both.

restart the phone

toggle usb debugging off and on

connect

use adb

click authorize