These are the basic steps to telling whether a keyvault is good or bad. This however does NOT determine whether a keyvault is banned or not
For this you will need:
Hex editor
And a keyvault lol
1.First off make sure the kv is along the lines of Kv_dec.bin it can be diffrent but as long as it has .bin at the end its ok. Also if it is 16.0KB
2.Once you have your kv open it up in Your favorite Hex Editor i am using Hxd
3.Once opened make sure there is 7 lines that are empty in the very beginning if it dosent have this right off the bat it is fake.
4. Make sure there is a large space in the kv it should separate two paragraphs
5.Make sure at the end it says Signature Cerification and certificatecollection at the end and there is a space at the very end with no writing at the bottom after the space.
Now i heard there is also a program called "Keyvaults modder" which can determine this as well, but because im old school ;D i prefer checking this way ^_^