Key File Extension
Key refers to Programme key file. Some softwares use this kind of extension. It can be opened by kaspersky software.
Some softwares save the passcodes on the file with key extension during the licencing.
For example these softwares use key files:
-AntiVir Personal Edition
-Avira product key
Softwares like Kaspersky may control passcodes on the internet, if you want to skip this process you can use better progammes like Nod32 instead of dealing with key file search.
If you buy the software, you should backup your key file properly. Because, the trojan files that get into your computer will try to search the files with key extension.
What needed to Open Key file extensions.
Kaspersky Anti virus software license process
Links about Key file extension