Encryption_key is missing in original site_config.json

I can’t get the encryption key in the original site1.local site_config.json file(it is missing), i only get the encryption key in my custom app site_config.json file which cause me encryption key is invalid.

Can i know the reason why encryption key is not present in site1.local ? where can i get it ? Note: i read some of the code and i realize in my db._Auth , the attribute encrypted is 0 of all Users, but the password is like encrypted string in db.