The Wifi master key is not a password to crack other people's encrypted wifi hotspots, but a known resource to gather free public wifi hotspots. If you search for wifi in the WiFi master key database, it will automatically connect. It doesn't allow you to access other people's encrypted wifi. If you entered a wifi before, you can't now. Maybe the owner of wifi didn't encrypt it before, but now it is encrypted, or you don't continue to enjoy wifi.
Cracking someone else's WiFi password is an invasion of others' privacy and an immoral act.
In fact, the easiest way is to ask him for the wifi password.