Part of macOS
securitydKeychain and security
○ Leave it
Looks after your passwords, keys and sign-ins.
What it is
Runs the keychain and handles authentication for apps and the system.
If you stop it
macOS starts it again straight away. Leave it.
The verdict
○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.
In Activity Monitor
securitydsecurityd_systemsecdcoreauthdauthd
From Procession’s guide, in the words the app shows.